OCCURENCE AND ABUNDANCE OF SELECTED PEST END BENEFICIAL
ARTHROPODS IN RELATION TO PEANUT PLANT
PHENOLOGY, IRRIGATION, AND INSECTICIDES.
by
IDRISSA OUSMANE AHIROU DICKO
B.S., Université de Ouagadougou
M.S., University of Georgia
A Dissertation Submitted to the Graduate Faculty of The
University of Georgia in Partial Fulfillment
of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
ATHENS, GEORGIA
1989
OCCURf:Ef\\C[ lU.) MWIW!Ir,CE or SEL ECTlD PEST /',rw CEr:rr l CJP,L
ARTH~orODS IN RELATION TO PEA~UT PLANT
Pr: EI.'J L(1 r. Y, lF: r ] Gf\\Tl 0ri, fI, ND H: S[ CTl Cl [) [ S
by
IDRISSA ousr'~M,E AMIROUDICKO
?-,-
A._
_ ,
.1
Approved:
Grad~
Date
RE~3UME DE LA THESE
NFLUENCE DE LA PHENOLOGIE DES PLANTS. L'IRRIGATION. ET LES INSECTICIDES
SUR L'ABONDANCE AU CHAMP nE~; INSECTE~: NUISIBLES ET DES
ARTHROPODES UTILES INFEOrES A L'ARACHIDE
JNIVERSITE DE GEORGIE. ATHENS USA. 1989
IDRISSA OUSMANE A. DICKO
2
INTRODUCTION ET JUSTICATION DE LA RECHERCHE
Les dégâts des insectes terricoles et du feuillage de
l'arachide, Arachis hypogaea L.,
sont évalués à des dizaines,
voire des centaines de millions de dollars américains chaque
année. Selon. Womack et al.
(1988),
les pertes de rendement
de l'arachide en Georgie,
dues seulement à quelques sept
espèces d'insectes nuisibles,
totalisent plus de 21 millions
de dollars US.
Ces pertes énormes ont conduit les paysans à
adopter l'utilisation systématique et abusive des insecticides
sans relation aucune avec la dynamique réelle des populations
des insectes nuisibles et de leurs ennemis naturels.
Cette
approche de lutte contre les insectes phytophages,
connue sous
le nom de "tape-mouche",
porte en elle-même les limites de son
utilité.
En effet, autant elle peut réduire les "symptômes" des
attaques des nuisibles,
autant elle n'affecte que peu ou pas les
conditions propices au pillulement de ces arthropodes
(Geir et
Clark,
1970).
il est aussi établi que l'utilisation fréquente et
non justifiée des insecticides conduit souvent à de nombreux effets
indésirables, dont
les plus cités sont les coüts de production
inutilement élevés
(French,
1971; Lynch et al,
1984),
la pollution
de l'environnement
(Belton,
1953; Beck,
et al.,
1962),
la destruc-
tion des arthropodes utiles,
notamment
les prédateurs et les parasi-
toïdes,) Smith et Jackson,
1975; Smith et al.,
1975), et l'apparition
de la résistance aux pesticides au sein des populations d'insectes
traités
(Luck,
1977). Aussi s'avère-t-il de plus en plus désirable
qu'une approche de lutte contre les nuisibles,
aussi efficace et
moins destructive de l'environnement que les insecticides,
soit
développée et mise à
la disposition des agriculteurs.
3
Depuis les travaux pionniers de French (1971),
la lutte
intégrée est l'approche préconisée pour minimiser les pertes de
rendement de l'arachide dues aux insectes déprédateurs.
la lutte
intégrée a été définie par les experts de la FAO (1980)
comme
étant un système de lutte aménagée, qui,
compte tenu du milieu
particulier et la dynamique des populations des espèces considérées,
utilise toutes les techniques et méthodes appropriées de façon aussi
compatible que possible en vue de maintenir les populations des
ravageurs è des niveaux où ils ne causent pas de dommages économiques.
En clair,
la détermination des seuils de dommages économiques et de
nuisibilité des insectes phytophages,
et ce, en rélation avec les
stades phénologiques de l'arachide les plus sensibles aux dégats
des nuisibles, demeure un préalable è la mise en place d'un
programme de lutte intégrèe. Un tel programme nécessite aussi
une connaissance approfondie de l'impact des méthodes de lutte,
potentiellemnt utilisables,
sur les populations des arthropodes
nuisibles, et la détermination de leurs effets sur les populations
des prédateurs et parasitoîdes. Tandis que de nombreux chercheurs ont
essayé de jeter les bases de lutte intégrée contre les insectes
nuisibles du coton (Bariola et al.,
1971; Byerly et al.,
1978;
Ellington et al.,
1984) et du soja (Dumas et al.,
1964; Farlowet
Pitre,
1983), peu de travaux semblabes ont porté sur les insectes
inféodés à
l'arachide.
L'objectif principal de la présente étude était de proposer
des solutions aux pertes de rendement de l'arachide dues aux attaques
des insectes nuisibles,
tout en cherchant è identifier l'impact de
ces solutions sur les populations des prédateurs et des parasitoïdes.
L'étude a porté sur quatre essais tous conduits au champ de 1987 à
1989 dans le sud de
l~ Georgie , USA.
4
I.
COMPARAISON DE L'EFFICACITE DES METHODES D'ESTIMATION DES
POPULATIONS DES INSECTES INFEODES A L'ARACHIDE
Idrissa O.
DICKO et Robert E.
LYNCH
(Résultats soumis pour publication
dans
le Journal of Agric Entomol.)
Le suivi permenent de l'évolution des populations des insectes
nuisibles et de leurs ennemis naturels,
au cours de la période
de croissance des cultures, est une nécessité pour le développement des
programmes de lutte intégrée.
Cependant,
comme l'a souligné Southwood
(1978),
il est pratiquement impossible de dénombrer tous les arthropodes
dans un habitat donné.
Aussi, doit-on souvent procéder à
l'estimation
des populations
par
la
pratique de l'échantillonnage.
Cette
constatation a conduit les chercheurs spécialistes de l'entomofaune de
l'arachide à proposer plusieurs méthodes d'échantillonnage devant
permettre le suivi des fluctuations des populations des arthropodes
associés à
la légumineuse au champ. Malheureusement,
chaque méthode
n'est potentiellemnt efficace que pour l'échantillonnage de quelques
espèces d'arthropodes données,
et ce en fonction de certains stades
de croissance bien précis de l'arachide au moment de
l'échantillonnage.
Ainsi, dans le cadre d'initiation d'un programme de lutte intégrée
contre les nuisibles de l'arachide,
en Georgie,
USA,
il s'est avéré
nécessaire de procéder à la comparaison de l'efficacité de plusieurs
méthodes d'échantillonnage utilisées routinièrement par les agents du
service de la vulgarisation agricole afin d'identifier celles qui
permettraient une quantification correcte et rapide des arthropodes
inféodés à l'arachide. Plus précisement,
la comparaison a été effectuée
entre les captures de quatre méthodes d'échantillonnage suivantes:
(1)
le filet fauchoir;
(2)
la methode d'echantillonnage par
5
prélèvements des fleurs;
(3)
la méthode d'échantillonnage par
prélèvement des bourgeons terminaux;
et
(4)
la méthode par prélèvement
et lavage des plants entiers.
Contre toute attente.
le nombre d'arthropodes collectés par la
méthode de prélèvement et lavage de plants entiers a été moins élevé
que ceux obtenus respectivement par les trois autres méthodes
d'échantillonnage. Seuls le filet
fauchoir et le prélèvement des
bourgeons terminaux ont permis de detecter les pics de populations
réflectant
les fluctuations "normales" des densités de principaux
insectes phytophages de l'arachide dans le sud de la Georgie. En effet.
la technique des bourgeons terminaux s'est révélée particulièrement
efficace pour l'estimation des populations des insectes de petites
dimensions.
tels que les immatures et les adultes des thrips.
Frankliniella fusca
(Hinds)
et les premiers stades larvaires des
Noctuidae appartenat aux espèces de Heliothis ~ (Boddie)
et de
Stegasta bosqueella
(Chambers).
Le filet fauchoir.
par contre. a
permis la capture d'un plus grand nombre d'insectes mobiles.
notamment
le jassid. Empoasca fabae
(Harris)
et l 'hemiptère prédateur.
Geocoris sp., et les derniers stades larvaires de H.
zea.
Ainsi,
il
.
- --
ressort de la présente étude que l'utilisation combinée des
méthodes d'échantillonnnage par les bourgeons terminaux et le filet
fauchoir suffirait à elle seule à générer assez d'information sur les
fluctuations saisonnières des populations de principaux
arthropodes
communément rencontrés dans l 'agroécosystème de l'arachide.
6
II.
DISTRIBUTION TEMPORELLE DES POPULATIONS DES ARTHROPODES INFEODES
A L'ARACHIDE EN RELATION AVEC LA PHENOLOGIE DES PLANTS
Idrissa O.
Dicko et Robert E.
Lynch
(Résultats soumis pour publication
dans J.
Agricultural Entomology)
Un des principes fondamentaux de
la lutte intégrée est
qu'aucune mesure de contr6le ne doit être prise à
l'encontre d'un
insecte nuisible à moins qu'il ait été prouvé que
l'insecte est
présent sur une culture donnée et qu'il y est en nombre suffisamment
élevé pour provoquer des dommages économiques
(Stern et al ..
1959;
Pedigo.
1986). Ce principe a stimulé de nombreux travaux de recherche
orientés vers l'identification de principaux facteurs déterminant les
fluctuations des populations des insectes nuisibles de l'arachide
(Leuck.
1967; Morgan.
1975; Lynch et Garner.
1980). Malheureusement.
la plupart des travaux n'ont porté que sur la dynamique des populations
d'une seule espèce d'insecte nuisible à
la fois.
Ceci est d'autant plus
regrettable que l'arachide.
au champ.
est toujours attaquée par un
ensemble d'insectes phytophages.
De même.
l'existence d'une relation
potentielle entre la phénologie de l'arachide et les densités au
champ des populations des insectes nuisibles n'a fait
l'objet que de
peu de recherche.
et ce.
bien que Smith (1980). Jones et al ..
(1982).
et Smith et Barfield (1982) aient montré que la réponse de l'arachide
à
la défoliation est fonction du stade phénologique des plants
au moment de la défoliation.
L'objectif de la présente étude était de déterminer la
distribution temporelle des insectes nuisibles de
l'arachide et de
leurs ennemis naturels associés
(prédateurs et parasitoïdes).
tout en
essayant d'établir la rélation entre les densités des populations de
ces arthropodes et la phénologie des plants.
7
La distribution temporelle des insectes nuisibles de
l'arachide et leurs ennemis naturels a été établie en 1986.
1987.
et 1988. à Tif ton.
en Georgie.
USA.
en échantillonnant hebdomadai-
rement les populations des arthropodes dans 6 parcelles. d'environ
1/4 hectare chacune.
Les méthodes d'échantillonnage utilisées étaient
le filet fauchoir et le prélèvement de bourgeons terminaux. méthodes
préalablement testées et prouvées efficaces pour l'estimation des
densités des arthropodes de l'arachide. Au cours de chaque année
d'expérimentation.
les échantillonnages sont effectués de mi-Juin à fin
Septembre. Les principaux stades phénologiques de l'arachide.
tels que
définis par Boote
(1982).
correspondant aux différentes périodes
d'échantillonnage étaient également notés.
Les densités de populations des thrips.
Frankliniella fusca
(Hinds).
les plus élevées ont été observées au cours des premiers stades
de croissance végétative de l'arachide.
Au cours de ces stades avant
floraison.
le nombre des thrips par bourgeon terminal de l'arachide
atteignait des densités de 4 à 5 thrips par bourgeon. dépassant ainsi
le seuil de dommages économiques qui est de 1 thrips par bourgeon
terminal.
Par contre.
les pics des populations des larves de principaux
lépidoptères phytophages de l'arachide que sont Heliothis zea (Boddie).
Elasmopalpus lignosellus
(Zeller).
et Stegast? bosqueella (Chambers),
n'ont été observés qu'au cours des stades de réproduction des plants
se situant entre la période de prolongation des gynophores et celle de
l'initiation des gousses.
Néanmoins,
au cours des 3 années d'expéri-
mentation,
les densités de populations des lépidoptères n'ont atteint
que rarement le seuil de dommages économiques évalué ct 4 larves par
0.30 m de ligne de semis.
Ces résultats montrent.
qu'à l'exception
peut-être des thrips.
les densités de la plupart des insectes
8
nuisibles sur l'arachide justifient rarement
les applications
systématiques d'insecticides telle qu'adoptées par les paysans
georgiens.
les populations des arthropodes prédateurs.
notamment les
araignées et Geocoris. généralement peu détectables en début de saison
culturale. augmentent graduellement au fur et à mesure que
la saison
progresse.
pour atteindre des densités sensiblenlent élevées entre
mi-Août et début Septembre de chaque année.
soit au des stades
phénologiques de
l'arachide correspondant à
l'initiation.
remplissage.
et maturation des gousses.
Les hyménoptères parasitoïdes.
tels que
Microplitis croceipes
(Cresson).
Pristomerus spinator (F.).
Cardiochiles
~igriceps Viereck. Netelia heroic~ Townes. et Meteorus sp .. sont
toujours plus abondants dans les parcelles d'observation au cours des
2 dernières semaines d'Août
(remplissage des gousses).
Ainsi.
au regard
des fluctuations temporelles des populations des arthropodes utiles.
en
Georgie.
il est probable que toute application insecticide non
selectif effectuée entre les stades phénologiques de
l'arachide allant
de
l'initiation à
la maturation des gousses risque de se faire aux
dépends des prédateurs et des parasitoîdes.
III.
INFLUENCE DE L'IRRIGATION SUR LES DENSITES DE POPULATIONS
DE PRINCIPALES ESPECES D'INSECTES NUISIBLES ET
D'ARTHROPODES UTILES INFEODES A L'ARACHIDE
Idrissa O. Dicko et Robert E. Lynch
(résultats en préparation pour publi-
dans le Journal Entomol. Science)
L'effet du déficit du sol en eau sur la croissance et la
réproduction des plants.
et sur la maturation des gousses et graines
9
de l'arachide a fait
l'objet de nombreux travaux de recherche de la
part des physiologistes. Boote et Hammond
(1981)
ont montré qu'un
déficit se produisant entre le 40ème et le 82ème jour après semis
réduirait la croissance végétative des plants d'arachide en interférant
avec le taux d'expansion des feuilles,
la formation des noeuds,
et
l'élongation des fanes ou tiges.
Lee
(1972)
observa qu'une humidité
rélative inférieure à 50% était susceptible d'influer négativement
sur la formation des fleurs et sur l'initiation et développement des
gynophores.
Cox (1977)
rapporta qu'un manque d'eau dans le sol
causerait des pertes de rendement d'autant plus élevées que
le manque se produirait au cours de
la phase phénologique de pleine
production des gynophores.
Contrairement aux physiologistes,
les entomologistes
se sont peu intéressés aux investigations sur l'effet potentiel du
déficit hydrique sur la distribution spatio-temporelle des arthropodes
de la légumineuse.
Les deux seules études du genre connues de nous sont
celle de Tappan et Gorbet
(1986)
conduite en Floride et les travaux de
Agnew et Smith (1989) menés au Texas.
Ainsi,
la présente étude a été initiée pour pallier au manque
d'information sur l'impact de l'irrigation artificielle sur les
populations des arthropodes de l'agroécosystème de
l'arachide,
surtout
que 45% des terres destinées à
la culture arachidière sont
systématiquement irriguées en Georgie. Nous nous sommes aussi
intéressés à
l'effet potentiel
indirect que pourrait avoir
l'irrigation de complément sur la distribution et dégâts des
mêmes arthropodes à travers son impact sur la croissance et
développement des plants.
10
L'expérimentation a été conduite en 1986 à Tif ton,
Georgie.
Le
dispositif expérimental utilisé était le dispositif blocs Fisher
randomisés à 2 traitements
(irrigation et non-irrigation ou témoin)
et à 5 réplications.
Les apports complémentaires en eau,
d'environ
20 mm par date d'irrigation,
ont été effectués par aspersion
(utilisation de sprinklers). Des irromètres,
implantés à 15 cm dans le
profil du sol,
ont été utilisés pour déterminer les périodes nécessitant
l'irrigation de complément.
Les densités de populations des arthropodes
ont été déterminées par des échantillonnages au filet fauchoir et par
prélèvement des bourgeons terminaux.
L'irrigation artificielle a significativement réduit les
populations des thrips,
Frankliniella fusca
(Hinds),
les larves du
lépidoptère Stegasta bosqueella
(Chambers),
et celles du lépidoptère
borer des racines et des gousses de
l'arachide,
Elasmopalpus
lignosellus
(zeller).
Les densités de populations de Heliothis zea
(Boddie)
ont été peu affectées par l'irrigation.
Bien que l'impact de
l'irrigation ait été minimal sur les densités de populations de
plusieurs espèces d'arthropodes prédateurs, y compris Geocoris sp.,
Nabis sp., Hippodamia convergens Guerin-Menville,
et Coleomegilla
maculata Lengi,
elle a favorisé significativement
l'augmentation du
nombre d'araignées prédatrices du genre Misumenops dans les parcelles
irriguées.
Ainsi,
il est apparu de notre étude que la pratique
d'irrigation artificielle pourrait
jouer un rOle important dans les
programmes de lutte intégrée.
En effet,
en plus de son impact direct
sur la croissance des plants,
l'irrigation
contribue effectivement
à
la réduction des populations de certaines espèces d'insectes
nuisibles et leurs dégâts sur l'arachide, mais aussi elle
11
favorise
la concentration de certains groupes d'arthropodes utiles
dans les parcelles irriguées.
IV.
EFFET DES APPLICATIONS INSECTICIDES SUR LES POPULATIONS
DES ARTHROPODES DE L'ARACHIDE
Idrissa O.
Dicko et Robert E.
Lynch
(résultats en préparation pour publication
dans le jornal of Economie Entomology)
Autant
les insecticides sont décriés de nos jours par les
environnementalistes a cause de leur effet quelquefois polluant.
autant ils sont considérés par les entomologistes comme devant être
une composante essentielle de tout programme de lutte intégrée contre
les insectes nuisibles.
En effet.
a chaque fois que les densités des
insectes ravageurs approchent les seuils de dommages économiques ou de
nuisibilité il existe peu de méthodes.
autres qu'insecticides
(toutes natures confondues).
qui soient capables d'éviter aux paysans
des pertes de rendements difficilement supportables
(Luck.
1977;
Knipling.
1979). Néanmoins,
l'utilisation des insecticides dans les
programmes de lutte intégrée nécessite une appréciation correcte de
leur impact sur les facteurs abiotiques et biotiques composant l'agro-
écosystème. Aussi.
devient-il de plus en plus souhaitable d'adjoindre
aux tests habituels d'évaluation de l'efficacité des insecticides
contre les insectes phytophages des volets d'études se rapportant a
la détermination de leurs effets sur les prédateurs et
les parasitoîdes
et sur le matériel végétal sur lequel
les tests sont conduits.
La présente étude a porté non seulement sur la quantification
de l'impact des applications insecticides sur les insectes nuisibles
de l'arachide et les arthropodes utiles. mais elle s'est aussi
12
intéressée à
la détermination de
l'effet direct de ces produits
chimiques sur la croissance et réproduction de la légumineuse.
Les essais ont été conduits en 1987 et 1988 dans des parcelles
expérimentales. d'environ 40 m de long sur 15 m de
large.
situées dans
la Station de Recherches de L'USDA.
à Tif ton.
Les trois traitements
suivants.
disposés en blocs Fisher à 6 répétitions.
ont été évalués:
(1) To:
traitement témoin;
(2) Tl:
traitement insecticide comportant
une application unique de Aldicarb
(Temik).
0.84 i.a/ha.
au semis. et
une ou de plusieurs applications de Chlorpyrifos
(Lorsban).
2.18 i.a
/ha.
et/ou Methomyl
(Lannate).
2.34 l/ha.
à
chaque fois que les densités
des insectes nuisibles atteignent
le seuil de dommages économiques;
et
(3) T2 Contrôle insecticide comprenant l'Aldicarb épandu au semis et 2
fois par semaine à partir des semis jusqu'à mi-Juillet
(40 jours)
plus
des pulvérisations hebdomadaires de Methomyl de mi-Juillet au début
Septembre de chaque année.
plus des épandages hebdomadaires de
Chlorpyrifos du début Juillet à fin Août.
La taille des populations du thrips. frankliniella fusca
(Hinds).
et du jasside. Empoasca fabae
(Harris).
dans les parcelles
ayant subi un seul traitement au semis à
l 'Aldicarb était significati-
vement plus petite que celle observée dans
les parcelles témoins.
De même.
les applications multiples de Methomyl ont causé une réduction
significative des densités de populations de Heliothis ~
(Boddie).
Néanmoins.
aucun des traitements insecticides n'a pernlis l'obtention de
de rendement en graines de l'arachide statistiquement plus élevé que
celui obtenu des parcelles non traitées.
Ces résultats confirment
le
fait que la pression des insectes nuisibles en Georgie ne justifie pas
toujours le programme d'applications systématiques d'insecticides tel
que pratiqué par les agriculteurs de la région.
13
Tous les traitements insecticides ont négativement affecté
les populations des arthropodes prédateurs. y compris Geocoris
sp., Nabis sp.
et de Misumenops sp. mais la réduction n'a été
significative que dans les parcelles ayant réeu des applications
multiples de Methomyl.
L'application de l'
Aldicarb au semis a
engendré une augmentation sensible des populations des larves de
li- ~ dans les parcelles ayant subi ce traitement. et ce. sans
qu'il ait eu une réduction significative du nombre des prédateurs.
Similairement,
la pesée hebdomadaire des plants.
faite conjointement
avec l'échantillonnage des insectes,
a montré que
l'application de
l'Aldicarb promotait la croissance végétative de l'arachide.
Ainsi,
il est probable qu'en stimulant la croissance foliaire,
l'Aldicarb
rendrait les plants de l'arachide plus attractifs aux femelles des
noctuidae gravides è
la recherche des sites de ponte.
Cette hypothèse
avait déjè été formulée par Rummel et Reeves
(1971)
et Morrison et al.
(1979)
pour expliquer l'augmentation du nombre des larves des lépidop-
tères nuisibles sur le coton et sur
le soja traités aux carbamates.
A notre connaissance,
par contre.
c'est la première fois que ce type
de relation possible entre l'arachide.
les carbamates.
et la taille des
populations des noctuidae phytophages a été signalé.
CONCLUSION
De l'ensemble des résultats de la présente étude,
l'on peut
tirer. entre autres.
les conclusions suivantes:
1.
les densités des populations de la plupart des arthropodes inféodés
a l'arachide au champ peuvent être efficacement estimées par
l'utilisation combinée du filet fauchoir et la méthode d'échantil-
lonnage par prélèvement des bourgeons terminaux.
Ces méthodes
14
peuvent d'autant plus être recommandées aux paysans qu'elles sont
peu chères.
rapides. et aisées a manipuler.
2. Telles que déternlinées par le filet
fauchoir et
la technique des
bourgeons terminaux.
les fluctuations temporelles des populations
des insectes nuisibles en Georgie.
USA.
a l'exception des thrips.
ne
justifient pas l'utilisation massive des insecticides telle que
pratiquée par les paysans de
la région.
Pire.
les applications
insecticides.
lorsqu'effectuées aux stades phénologiques de
l'arachide allant de
l'initiation a la maturation des gousses.
pourraient sérieusement nuire aux arthropodes prédateurs et
parasitoîdes qui habituellement contribuent au contrOle naturel des
populations des nuisibles.
3.
La pratique de
l'irrigation artificielle pourrait être une composante
importante du programme de
lutte intégrée car non seulement elle
permet de réduire
les populations et les dégâts de insectes
nuisibles de l'arachide.
tels que Frankliniella fusca
(Hinds).
Stegasta bosqueella
(Chambers).
et Elasmopalpus
lignosellus
(Zeller).
mais aussi.
elle favorise
l'augmentation du nombre des prédateurs
dans les parcelles irriguées.
4.
Bon nombre de traitements insecticides ne sont pas toujours
justifiés sur la base de pertes réelles de rendement de l'arachide.
en Georgie. Mieux.
l'utilisation de certains produits insecticides.
notarrunent
les formulations granulées des carbamates.
pourrait
promouvoir une croissance foliaire abondante aux dépends
de la fructification de
l'arachide et aussi provoquer une
augmentation des densités des populations des
larves des
lépidoptères
nuisibles.
--'~--
15
REFERENCES CITEES
FAO.
1980. La lutte intégrée contre les insectes nuisibles du
sorgho.
Rome.
Italie.
Pour le reste des références citées dans le corps du texte.
prière
bien vouloir consulter la lisle complête des références figurant
dans les copies de
la thèse ci-jointes.
,',!
DJ CEO
CI. ~ P;-l t'il\\ ~
('; \\.;
~":., _ ~ !il,-j i.: '·::_.'l:~.l ( li
i t : t i..ll:.: l , : c • '. ; l i
r, r l ): 1 (; ,[, ,: : ':, f, l l < t i (' :, t fI r t l:, [,', r' i,:, i !: ,( " ( l (1 ~l,\\ , ]) 1 ; l ',: \\ ,l,
lnscct icidl's,
(L1ndé!' the direct iOIl of RClLCf;l E. Lyr;U;)
Influence of plant phenol ogy, irrigation, and insecti(id~s on
seasonal abund~nce of selected pest and beneficial arthropods in
peanut was evalusted at Tif ton, GA.
Pest species includcd,
frankl'iniella fu~ca (Hinds), Stegasta bosoueella (Chambers), Heliothis
zea (80ddie), Elasr;,oralpus lignosellus (Zeller), and Empoascè fahae
(Harris).
1he seasonal abundance of beneficial arthropods, Grius
insidiosus (Say), Geocoris spp., nabids, spiders, and parasitoids was also
evaluated.
Population estimates of these arthropods were cor~ared
during the 3-year study using whole plant, te!'~inal, flower. 21d sweEp
net sampling methads.
lhe sdmpling efficiencies of the four methods varied with
devel!'p'm~lJtal stage and feeding behavior of a particular species.
HO\\·lev~~,~.t was found that a cornbination of terminal examination and
s\\'leePI~(çould yield valuable information about the seasonal cbundarlce
of most ~rthropods associated with peanut.
Converted to quantitative
val ues, 1. e ., "pel- pla nt" value s, pop ulat i Cfi est i mat es by thE ~ e hw
sampling ffiethods are li~ely to provide more reliable information than
.'
./
beat and shake methods;presently used to sample peanut insects.
~
~
Thrips populations in terminals reached peak densities in early
vegetative stages, but declined sharply at the onset of flowering.
Densities of H. zea, f. lionosellus, and~. boscueella coincic€:d
~ith pe2nut gfowth stag~s most susceptibl~to damage.
Highest predator
In 1986, overht:'éld irrigation significantly reduced pO~lulètions of
thrips, red-necked peanutworm, and lesser cornstalk borer larvae, while
increasing infestations by potato leafhopper.
Irrigation had little
impact on populations of corn earworm larvae or predators, with the
exception of spiders whose populations were significantly higher in
irrigated than in nonirrigated peanut.
Aldicarb applied at planting effectively controlled thrips and
potato leafhopper infestations, but encouraged an increase in H. zea
larval populations.
Combined applications of aldicarb, methomyl, and
chlorpyrifos controlled thrips, leafhoppers, and corn earworm.
However,
none of the insecticides had a significant effect on larvae of ~.
bosqueella or I. liqnosellus.
Populations of Geocoris spp., nabids, and
spiders were reduced by multiple insecticidal applications.
Under pest
population levels encountered in this study, insecticides did not
significantly increase pod yield.
INDEX WORDS: Peanut Growth Otages, Seasonal Abundance, Sampling
Methods, Irrigation, Insecticides, Frankliniella
fusca, Steqasta bosqueella, Hel iothis zea,
Elasmopalpus liqnosellus, Empoasca fabae,
Predators, Parasitpids
/
ACKNOWLEOGEMENTS
First and foremost, l would like to thank my advisor, Or. Robert E.
Lynch, for his guidance, support, and most of all, for his patience and
friendship.
am also extending my gratitude to my committee members,
Ors. Arden Lea, Charlie Rogers, Jim Outcher, and John All.
To the late
member of my committee, Or. Eugene Brady, l would like to say rest in
peace, and may God accept you for what you were:
A good man and a good
teacher.
A special thank you to Dr. Oarl Snyder and his colleagues, Mrs.
Bernadette Allard, Eva Miller, and Edna Fischer for their warm
friendship and support.
Vou really made me feel at home.
My deepest gratitude to Mr. Richard Layton, Mr. Lloyd Copeland,
Ors. Willard Wynn and Alex Huryn, and Mrs. Louise Brice.
l would not
have made it without your cooperative help.
To my true friends, Aime Joseph Nianogo and his family, Oerek
Focho, Constantin Zana Somda, Hsiao Wen Feng, and Francois NGuessan, l
would like to simply say thank you for the wonderful memories at The
Un i vers ity of Georg i a.
.1
!
iv
OEDICATION
To my family, Odile, Nassirou, Souley, and to all my brothers and
sisters, Bassirou, Nassourou, Abdouramane, Oumar, Souley, Salou, and
Diaratou.
To all the people of Dori and Burkina Faso.
./
1
i i i
TABLE OF CONTENTS
DEDICATION.......................................................
iii
ACKNOWLEDGMENTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
i v
LIST OF TABLES...................................................
ix
LIST OF FIGURES..................................................
xv
CHAPTER l : GENERAL INTRODUCTION
.
CHAPTER II : REVI EW OF LITERATURE.. .. . .. .. .. .. .. . .. .. .. .. .. . . . .. .
3
Literature Cited............................................
13
CHAPTER III : COMPARISON OF METHODS FOR SAMPLING
INSECTS ASSOCIATED WITH PEANUT....................................
23
Abstract
" . . . . . . . . . . . . .
. . . . .
24
Introduction.................................................
2.5
Materi al sand Methods........................................
27
Results and Discussion.......................................
30
Conclusions
'.
37
Literature Cited.............................................
76
CHAPTER IV : SEASONAL ABUNDANCç OF SELECTED PEANUT
PESTS AND BENEFICIAL ARTHROPODS AS INFLUENCED BY
PLANT PHENOLOGY ........................•.......................... 80
Abstract .. " . . . . . . ... . . . . . . ... . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . .
81
Introduction.................................................
82
Materi al sand Methods........................................
83
Results and Discussion
86
v
vi
Conclusions.................................................
98
Literature cited............................................
133
CHAPTER V : EFFECT OF IRRIGATION ON POPULATIONS OF
PEST AND BENEFICIAL ARTHROPODS OF PEANUT
139
Abstract ..... , . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .
140
Introduction................................................
141
Materials and Methods.......................................
142
Results and Discussion......................................
143
Conclusions.................................................
149
Literature Cited............................................
160
CHAPTER VI : INFLUENCE OF INSECTICIDE APPLICATION REGIMES
ON PEANUT AND PEANUT ARTHROPODS.
164
Abstract....................................................
165
Introduction................................................
166
Materials and Methods.......................................
168
Results and Discussion......................................
170
Concl us ions
': . . . . . . . . . . . . . . . . . .
183
Literature Cited............................................
204
CHAPTER VII: GENERAL CONCLUSIONS.......
211
LITERATURE CITED.................................................
216
.1
APPENDIX
.;.....................................
236
1
Table 3-2. Relative frequencies for arthropods
collected in peanut by four sampling methods,
Tifton, GA., 1986.
237
Table 3-3. Relative frequencies for arthropods
collected in peanut by four sampling methods,
Tifton, GA., 1987..........................................
242
vii
lable 3-4. Relative frequencies for arthl"Opods
collected in peanut by four sampling methods
lifton, GA., 1988
247
LI ST OF TABLES
Table
Page
3-1
Schedule of sampling dates for estimating
arthropod populations in pean ut at Tifton,
GA, 1986-1988.
67
3-5
Mean population density estimates for insects
in peanut at Tif ton, GA, as obtained by four
samp li ng methods, 1988. .
.
68
4-1
Average monthly rainfall in Tifton, GA, 1986-
1988.
115
4-2
Sampling dates and ccrres~onding peanut growth
stages, 1986-1988.
116
4-3
Seasonal abundance of immature and adult thrips,
Frankliniella fusca ~Hinds), in peanut
at Tifton, GA, colle:ted from different growth
stages of plants, 1986-1988
.
117
'4-4
Seasonal abundance of larvae and adults of the
corn earworm, Heliothis zea (Boddie), in
,1
peànut at Tifton, GA, collected from different
!
growth stages of plants, 1986-1988
.
119
4-5
Seasonal abundance of larvae and adults of the
lesser cornstalk borer, Elasmopalpus lignosellus
vii i
ix
Table
Page
(Zeller), in peanut at Tifton, GA, collected from
different growth stages of plants, 1986-1988
121
4-6
Seasonal abundance of the red-necked peanutworm,
Stegasta bosqueella (Chamb.), larvae in peanut
at Tifton, GA, collected from different growth
stages of plants, 1986-1988
123
4-7
Seasonal abundance of adult potato leafhoppers,
Empoasca fabae (Harris), in pean ut at Tifton,
GA, collected from different growth stages of
plants, 1986-1988.
125
4-8
Seasonal abundance of predators collected from
different growth stages of peanut at Tifton, GA,
1986-1988
127
4-9
Combined numbers of predators / sweep sample as
related to pean ut plant phenologies, Tifton, GA,
1987-1988.
129
4-10
Seasonal abundance of adult parasitoid wasps,
Microplitis croceipes (Cresson), Pristomerus
spinator (Fabricius), and Netelia heroica
,1
Townes, Cardiochile~ nigriceps Viereck, and
Meteorus sp. collected from peanut at Tifton,
GA, 1986-1988. . ...'. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
131
5-1
Rainfall and supplemental irrigation for
Florunner peanut grown under irrigated and
nonirrigated conditions in Tifton, GA., 1986
151
x
Table
Page
5-2
Effect of irrigation on populations of tobacco
thrips, Frankliniella fusca (Hinds),
infesting Florunner peanut, Tifton, GA, 1986
152
5-3
Effect of irrigation on populations of
Heliothis zea (Boddie), Stegasta
bosqueella (Chamb.), and Elasmopalpus
lignosellus (Zeller), larvae infesting
Florunner peanut, lifton, GA, 1986
153
5-4
Effect of irrigation on populations of
adult Heliothis zea (Boddie), and
Elasmopalpus lignosellus (Zeller),
infesting Florunner peanut, lifton, GA,
1986
154
5-5
Effect of irrigation on populations of
potato leafhopper, Empoasca fabae
(Harris), infesting Florunner peanut,
lifton, GA, 1986.
155
5-6
Effect of irrigation on populations of
predators on Florunner peanut, lifton,
GA, 1986
156
5-7
Influence of irrigation on plant density,
number of pegs and pods for Florunner peanut,
Tifton, GA, 1986.
157
5-8
Influence of irrigation on fresh weight of
Florunner peanut plants, Tifton, GA, 1986.
158
xi
Table
Page
5-9
Influence of irrigation on dry weight of
Florunner peanut plants, Tifton, GA, 1986.
159
6-1
Effect of insecticides on populations of
tobacco thrips, Frankliniella fusca (Hinds),
immatures in Florunner peanut, Tifton, GA,
1987-1988
186
6-2
Effect of insecticides on populations of tobacco
thrips, Frankliniella fusca (Hinds), adults
in Florunner peanut, Tifton, GA, 1987-1988.
187
6-3
Influence of insecticides on foliage damage
by insects to Florunner-~~anut, Tifton, GA.,
1987-1988.
188
6-4
Effect of insecticides on populations of
of red-necked peanutworm, Stegasta bosqueella
(Chamb.), larvae in Fiorunner peanut, Tifton, GA,
1987 -1988 . .
' ,' :
,
189
6-5
Effect of insecticides on populations of corn
earworm, Heliothis zea (Boddie), larvae
in Florunner peanut, Tifton, GA, 1987-1988.
.a9D
6-6
Effect of insecticides on populations of corn
1,
earworm Heliothis zea (Boddie), moths
in Florunner peanut, Tifton, GA, 1987-1988.
191
6-7
Effect of insecticides on populations of
potato leafhopper, Empoasca fabae (Harris),
adults in florunner peanut, Tifton, GA.,
1987-1988.
192
xii
Table
Page
6-8
Effect of insecticides on populations of
lesser cornstalk borer, Elasmopalpus
lignosellus (Zeller), larvae in Florunner
peanut, lifton, GA, 1987-1988
193
6-9
Effect of insecticides on populations of
lesser cornstalk borer, Elasmopalpus lignosellus
(Zeller), moths in Florunner peanut, lifton, GA,
1987-1988.
194
6-10
Effect of insecticides on populations of
spiders in Florunner peanut, lifton, GA,
1987-1988.
195
6-11
Effect of insecticides on total predator
populations in Florunner peanut, lifton
GA., 1987 -1988.
196
6-12
Effect of insecticides on populations of
parasitic Hymenoptera in Florunner peanut,
lifton, GA, 1987-1988
197
6-13
Influence of insecticides on plant density
and reproductive st~pctures of Florunner
peanut, lifton, GA.{ 1987-1988
198
6-14
Influence of insecticides on fresh weight
of Florunner peanut plants, lifton, GA,
1987-1988
200
6-15
Influence of insecticides on dry weight
of Florunner peanut plants, lifton, GA,
1987-1988
201
xiii
Table
Page
6-16
Influence of insecticides on yield of
Florunner peanut, lifton, GA., 1987-1988
202
6-17
Pearson correlation coefficients for selected insect
pest species versus dry weight of above ground
vegetative structures and pods of Florunner peanuts
203
i
~.;:--
i
.~ 1 .,.
l _ J. ~.' .i.':
F) ,.
Figu!'2
3-?
xv
Figure
Page
3-6
Combined population estimates of nymphal
and adult potato leafhopper, Empoasca fabae
(Harris) in peanut at Tifton, GA, determined by
three sampling methods in 1988
49
3-7
Estimates for corn earworm, Heliothis zea
(Boddie), in peanut at Tifton, GA, determined
by three sampling methods in 1986-1987
51
3-8
Estimates for corn earworm, Heliothis zea
(Boddie), in peanut at Tifton, GA, determined
by three sampling methods in 1988.
53
3-9
Estimates for red-necked peanutworm, Stegasta
bosqueella (Chamb.), in pean ut at Tifton, GA,
obtained by three sampling methods in 1986-
1987
55
3-10
Estimates for red-necked peanutworm, Stegasta
bosqueella (Chamb.), in peanut at Tifton, GA,
determined by three sampling methods in 1988.
57
3-11
Population estimates for nymphs and adults of
Geocoris spp. in peanut at Tifton, GA,
determined ~y two methods in 1986-1987.
59
3-12
Population estimates for nymphs and adults of
Geocoris spp. in peanut at Tifton, GA,
determined by two sampling methods in 1988.
61
xvi
Figure
Page
3-13
Population estimates for nymphs and adults of
Orius insidiosus (Say) in peanut in Tifton,
GA, determined by four sampling methods in
1986-1987.
63
3-14
Population estimates for nymphs and adults of
Orius insidiosus (Say) in peanut at Tifton,
GA, determined by four sampling methods in
1988
65
4-1
Seasonal abundance of the tobacco thrips,
Frankliniella fusca (Hinds), in peanut
at Ti fton, GA, 1986-1988. .
101
4-2
Seasonal abundance of corn earworm, Heliothis
zea (Boddie), moths and larvae in peanut at
Tifton, GA, 1986-1988
103
4-3
Seasonal abundance of lesser cornstalk borer,
Elasmopalpus lignosellus (Zeller), moths and
larvae in pean ut at Tifton, GA, 1986-1988
105
4-4
Seasonal abundance of red-necked peanutworm,
Stegasta bosqueella (Chamb.), larvae
in peanut at Tifton, GA, 1986-1988:
107
4-5
Seasonal abundance of adult nabids, lady
beetles, Geocoris spp. and spiders
co 11 ected From pea-nut at Ti fton, GA,
1986-1988
109
xvii
Figure
Page
4-6
Seasonal abundance for combined predator
species collected from peanut at Tifton,
GA, 1987-1988
111
4-7
Seasonal abundance of adult parasitic wasps,
Microplites croceipes (Cresson), Cardiochiles
nigriceps Viereck, Pristomerus spinator (F.)
Netelia heroica Townes, Meteorus sp. collected
from peanut at Tifton, GA, collected on different
growth stages of plants, 1987-1988
113
.1
!
-1
- -
1.
GENERAL INTRODUCTION
Damage to peanut, Arachis hypogaea L., by soil and foliar insects
amounts to tens, if not hundreds of millions of dollars each year.
According to Womack et al. (1988), losses in peanut in Georgia due to
seven insect species alone were over $21 million in 1986.
These drastic
lasses have prompted most farmers to adopt a systematic spraying
timetable for peanut pests based on little or no knowledge of the
dynamics of pest and beneficial insect populations.
This 'fly-swat'
approach to insect control often bears the causes for its limited
success, for it may only reduce symptoms while leaving unaffected the
circumstances which induce pest outbreaks (Geir and Clark 1970).
Indiscriminate use of insecticides also leads to many undesirable
effects, such as , unnecessary control costs (French 1971, 1973, Lynch et
al. 1984), undesirable build-up of insecticidal residues (Belton 19~3,"
Beck et al. 1962), and destruction of beneficial insects (Smith and
Jackson 1975, Smith et al. 1975).
Therefore, it is desirable to develop
more comprehensive pest control methods which minimize both crop losses
and ecological disturbances.
Integrated pest management (IPM) is the most appropriate approach
for the control of insect pests of peanut.
One of IPM's most basic
principles is that no control measures be undertaken against a pest
species unless it is known that the pest is present and/or the pest is
present in a sufficient density to cause economic loss (Stern et al.
1
2
1959, Pedigo et al. 1986).
Thus, any sound IPM program relies on an
adequate knowledge of insect population levels conducive to crop damage
and requires the determination of plant growth stages most likely to be
damaged by such populations.
It also necessitates a better
understanding of the impact of applied control measures on populations
of both pests and beneficial insects, as well as their impact on the
dynamics of crop growth and yield.
While cotton and soybean insects
have been intensively investigated in recent years, such crucial
information on the ecosystem of the peanut crop is generally lacking.
Similarly, few studies have attempted to address the possible negative
effects of cultural and chemical control methods, routinely aimed at
peanut insect pests, on populations of beneficial arthropods associated
with peanut plants.
The purpose of this study is to investigate the insect fauna of -
peanut encountered in South Georgia, with special consider3tion for
identification of pest and beneficial insects and the qua~tification of
populations of these arthropods at all the major growth s~ag~s of
peanut.
The effects of cultural practices, such as irrigati0n and
insecticide application, on populations of arthropods commonly
associated with growing peanut were evaluated.
Finally, several of the
methods used to sample pean ut insect pests were evaluated to determine
their efficiencies with specific insect species.
2
1959, Pedigo et al. 1986).
Thus, any sound IPM program relies on an
adequate knowledge of insect population levels conducive to crop damage
and requires the determination of plant growth stages most likely to be
damaged by such populations.
It also necessitates a better
understanding of the impact of applied control measures on populations
of both pests and beneficial insects, as well as their impact on the
dynamics of crop growth and yield.
While cotton and soybean insects
have been intensively investigated in recent years, such crucial
information on the ecosystem of the peanut crop is generally lacking.
Similarly, few studies have attempted to address the possible negative
effects of cultural and chemical control methods, routinely aimed at
pean ut insect pests, on populations of beneficial arthropods associated
with peanut plants.
The purpose of this study is to investigate the insect fauna of
pean ut encountered in South Georgia, with special consideration for
identification of pest and beneficial insects and the quantification of
populations of these arthropods at all the major growth stages of
peanut.
The effects of cultural practices, such as irrigation and
insecticide application, on populations of arthropods commonly
associated with growing peanut were evaluated.
Finally, several of the
,1
methods/used to sample peanut insect pests were evaluated to determine
their efficiencies with specifie insect species.
II.
REVIEW OF LITERATURE
The Peanut Plant
The peanut, Arachis hypogaea L., is a legume native of Bolivia.
From its South American origin, the pean ut was disseminated to Europe,
both coasts of Africa, Asia, and the Pacifie Islands (Hammons 1973).
Today, peanut is grown in many parts of the world on more than 17
million hectares as an important vegetable oil and food crop.
Worldwide, it ranks thirteenth in importance among the row crops (McGill
1973).
The leading peanut growing nations include India, China, the
United States, Seneghl, and Nigeria.
The farm value of peanut in the
United States is estimated at approximately $750 million annually, with
the state of Georgia producing 41% of the nation's harvested crop
(Henning 1978, Morgan 1979).
Factors affecting peanut plant growth, development, and yield
include soil ty~e and moisture, temperature, solar radiation, peanut
variety, fertilizers and other agricultural inputs.
The peanut crop's
responses to water deficiency or drought at various growth stages has
been intensively investigated.
Pallas et al. (1979) réported that
drought is generally implicated in causing low yield, poor seed grades
and germination, and increased incidence of aflatoxin in the kernels.
The effects of drought on peanut yield have been shown by Martin and Cox
(1977), and Boote and Hammond (19Bl) to vary according to the intensity
of the stress, duration of the drought, and stage of the crop affected.
3
4
The period of peanut growth from flowering to pod fill is the most
susceptible to soil water deficiency (Saini and Sandhu 1973, Henning
1978, Stansell and Pallas 1985).
On the other hand, excessive rainfall
or irrigation may have negative effects on pean ut yield by promoting
excessive vegetative growth (Boote et al. 1982), increasing the severity
of several diseases (Wright et al. 1986), and pod loss in the soil at
harvest (Gorbet and Rhoads 1973).
Temperature and solar radiation also play a major role in the
development of the peanut plant.
Cox (1979) reported that the
temperature requirement for the accumulation of dry matter by the above
ground parts of the plant varies with the peanut vegetative stage, with
the optimum temperature for maximum growth during the early stages being
higher than the temperature required during the later growth stages.
Investigations indicate that reduced solar radiation during peak
flowering reduces the number of flowers per plant, and that flowers
opening at the time of shading do not produce pegs (Cox 1978, Hang 1978,
Hang et al. 1984).
Peanut is a peculiar crop plant in that flowers are produced above
ground and fruit is produced below ground.
Smith (1954) reported that
while peanut plants usually flower profusely, only a relatively small
proportion of(the ovaries mature because many pegs fail to reach the
soil or others often fail to enlarge and produce pods.
Bear and Bailey
(1973) showed that a high proportion of the pods that develop on a
pean ut plant are derived from the first twenty flowers produced, with
the potentiàl for a flower to give rise to a mature fruit decreasing as
flowering progresses.
Thus, there is not direct linear correlation
5
between various yield componrnts, i.e. flowcrs and pegs, and tllc
actual yield obtained at harvest.
In many respects, the indeterminate
flowering habit of peanut is unfavorable for the production of high
yield, since it may increase the number of harvested immature peanut pods
and/or delay harvest (Rahman and Ali 1970).
Insect Pests and Damage to Peanut
Literature dealing with insect pests of peanut is extensive (Smith
and Barfield 1982).
Therefore, this review addresses only the major
pest species associated with pean ut grown in South Georgia.
Several
methods have been used to classify pean ut pests.
Huffman (1974)
classified insect pests of peanut as primary and secondary, while Bass
and Arant (1973) based their classification according to plant parts
attacked to differentiate between soil (root and peg), and foliage
feeding (above ground) species.
Although neither of the above
classifications is strictly accurate, the latter method is adopted here
for convenience.
The most frequently encountered species of above-groJnd pests of
peanut are thrips, the most common of which is the tobacco thrips,
Frankliniella fusca (Hinds), flower thrips, I. tritici (Fitch) and I.
bispinosa (Morgan) (Lynch et al. 1984).
Thrips are early season pests
which initially move into pean ut fiel~s from wild plants or other
cultivated crops.
Damage by thrips is typically confined to seedling
peanut, and most of their in jury is caused by the feeding within the
folded leaflets which produces distortion and malformation of expanded
leaves.
In unusually heavy thrips infestations, the entire plant may be
severely stunted or even killed (Poos 1941, Belton 1953).
As the plants
6
develop, the intensity of thrips in jury declines sharply (Tappan and
Gorbet 1979, 1981: Lynch et al. 1984).
This decl ine in thrips in jury
often parallels a reduction in the number of thrips in terminals.
The principal method for controlling thrips in peanut is through
the use of systemic granular insecticides typically applied at planting
time.
Lynch et al. (1984) reported that more than 60% of the pean ut
acreage in Georgia received a systemic insecticide at planting for
thrips control from 1979 to 1981.
However, the economics of thrips
control with insecticides has been questioned, if not rejected, by
various authors (Arthur and Arant 1954, Bass and Arant 1973, Tappan and
Gorbet 1981. Lynch et al. 1984).
The potato leafhopper, Empoasca fabae (Harris), is found primarily
in the eastern and midwestern United States, as well as in parts of
Canada and Mexico.
lt overwinters in Southern states where it breeds
continuously alollg tile Gulf (Gyrisco et al. 1978).
As the weather warms
in the early sum~ier, the leafhopper spreads northward where it attacks a
variety of summ~r aild fa" crops, including potato, beans, clover,
alfalfa, soybean, and peanut.
The wide range of host plants attacked,
added to its numerous generations each year are thought to be
significant factors contributing to 1. fabae abundance ~nd its place
among the major insect pests of peanut in the Southern ~nited States
(Belton 1953).
Injury to pean ut by the potato leafhopper is causèd by both adults
and nymphs sucking plant fluids, principally from the lower epidermis
and veins of the leaves.
Additional damage to the plant also may result
from the depos it i on of eggs in the pet i 0 l es and stems by adult fema les
7
(Bass and Arant 1973).
Symptoms of plant in jury caused by the patata
leafhopper include yellowing and necrosis of the tips of peanut
leaflets, often called "hopperburn", and plant defoliation in cases of
severe infestations.
As with thrips, the most damaging infestations
of I. fabae occur early in the season (E11 is 1984).
The primary means
of controlling the patata leafhopper in peanut is through chemical
application and ta a lesser extent, the use of insect-resistant peanut
cultivars (Campbell and Emery 1971, Campbell and Wynne 1985).
The red-necked peanutworm, Stegasta bosqueella (Chamb.), is a mid-
to-late season insect pest that causes occasional damage to peanut.
It
has been reported ta feed on several species of plants, but peanut seems
to be its preferred hast.
Larval feeding is almost exclusively confined
to unopened leaflets of terminal buds, where the caterpillars scar the
surface or eat holes through the leaflets.
Leaflet in jury often results
in impaired or suppressed bud production, and sometimes leads to
malformation and shortening of the shoots (Bissell 1941, Walton and
Matlock 1959).
Wall and Berberet- (1979), using a mechanical stimulation
technique to simulate damage in terminal buds caused by the larvae of
the red-necked peanutworm, reported that the ability of terminal
leaflets to compensate for damage decreases with maturity.
Reports have
./
indicated no significant yield gains in peanut from chemical control of
/
the red-neckedpeanutworm (Arthur et al. 1959, Berberet 1978, Berberet
and Guil avogui. 1980).
The corn earworm (cotton bollworm), Heliothis zea (Boddie), is a
common insect species on peanut in South Georgia (Morgan 1979).
The
corn earworm is a highly polyphygous species that feeds on a wide
variety of crops, including corn (its preferred host), tomato, cotton,
sorghum, several weed species, and many other plant species.
In most
of the southern areas of its distribution, corn earworm moths emerge
from overwintering pupae from early March to April, before corn
becomes attractive for oviposition, and lay eggs on a variety of
uncultivated and cultivated plants.
Moths, whose larvae developed on
these early season wild host plants, shift oviposition to corn as it
begins to silk, and remain concentrated on this crop for about 2
months.
After completion of silking by corn, there is again a decided
shift by H. zea to a variety of hosts such as alfalfa, cotton and
peanut (Dicke 1939).
The most damaging population of corn earworm
larvae on peanut occurs in early August (~10rgan 1979).
On pû"lnut,
corn earworm eggs are laid on the undersurface of leaves, primarily in
the upper portion of the peanut canopy (Pencoe and Lynch 1982).
Initial larval damage to peanut foliage is restricted to ter~inal buds
and flowers.
Severe damage to peanut, however, is causee; by feeding
of later instar larvae on leaves, which under high populdti0n
densities may cause complete defoliation of plants.
Lynch and Garner
(1980) reported that defoliation is greatly enhanced by delayed
planting of peanut.
Successful control of corn earworm larval
populations on pean ut using insecticides has been reported by several
authors (Kennedy et al. 1987, Sams and Smith 1979).
All et al.
(1977) indicated that normal chemical dosages for controlling
H. zea larvae can be reduced to O.lx of current recommendation
by using mixtures of methomyl, permethrin and pydrin.
However,
control of H. zea populations is generally hindered by the migratory
9
habit of the moths, which enables immigration of new maths into
previously treated fields (Snow et al. 1969, Sparks 1972).
This
important biological attribute of the corn earworm has prompted many
scientists to argue for control of the pest through the use of
adulticides (Mitchell et al. 1965, Chauthani and Adkisson 1966"
Lincoln et al. 1966, Phillips and Lincoln 1968, Young et al. 1972,
Herzog and Phillips 1987).
Among the soil insect pests that damage
peanut, the lesser cornstalk borer (LCS), Elasmopalpus lignosellus
(Zeller), is probably the most destructive.
Peanut yield losses
caused by the LCS have been estimated to amount to millions of dollars
each year (Mack et al. 1982).
Leuck (1967) reported that the bulk of
these losses in Gecrgia result from larval boring and feeding on pegs
and pods.
Larv~e damage immature pods by feeding on the developing
kernels (Lynch 1984).
Larval damage to more mature pods is generally
confined to external scarification without pod penetration.
In
addition, damage to peanut pods by the lesser cornstalk borer also may
enhance increa~ed aflatoxin contamination of peanut kernels (Wilson
and Flowers 1978).
Among the factors that are known to cause 1.
lignosellus populations to reach epidemic proportions, soil texture,
water, and temperature are probably the most important! (Luginbill and
Ainslie 1917, French 1971, Mack et al. 1987b).
The cryptic nature of
the LCS and its soil habitat make evaluation and control of
populations difficult.
Although All et al. (1979) hive demonstrated
that several cultural practices could substantially lower LCS
infestations, the use of granular pesticides remains the principal
control strategy of choice in peanut.
la
Beneficial Insects:
Predators and Parasites of Peanut Pests.
The list of arthropod predators and parasites known to attack
insect pests in peanut and other field crops is quite extensive.
Whitcomb and Bell (1964) reported that over 600 species of arthropod
predators occur in Arkansas cotton fields.
Of these, 10 to 15 families
belonging to Hemiptera, Neuroptera, Coleoptera and Araneida are probably
the most important.
The number of important species of parasites
attacking pean ut pests is believed to be much smaller than the number of
predators (Ridgway and Lindgren 1972).
Several species of Geocoris (big-eyed b~gs), i.e., li. punctipes
(Say), li. uliqinosus (Say), li. pallens Stal, and li. bullatus (Say), are
general predators in agricultural systems.
The most common big-eyed bug
in pean ut is li. punctipes (Davis 1981, Mack et al. 1987a).
Geocoris
spp. begin immigrating into peanut fields shortly after seedling
establishment, increase to maximum density by mid-July to mid-A~gust,
and then decrease in density through October (Davis 1981).
As
predators, big-eyed bugs have a wide range of hosts among 67 species of
small prey from 3 classes of arthropods (Insecta, Arachnida, and
Diplopoda) (Crocker and Whitcomb 1980).
Thus, as opportunitic
polyphagous predators, Georcoris spp. may play an important l'ole in the
.1
control of pesr outbreaks (Van Den Bosch et al. 1969). Factors
limiting populàtion increase of big-eyed bugs include predation by other
arthropods, such as Nabis and spiders, parasitism by Telenomus spp.,
cannibalism, and pesticides (Cave and Gaylor 1988, Atim and Graham
1984).
1]
Another important predator of pcanut pests is the insidiosus flOWCI'
bug, Orius insidiosus (Say).
Although Q. insidiosus has been }'eported
to destroy a large number of eggs and first-instar larvae of H. zea in
corn, its contribution to natural control of peanut insect pests is
through feeding on thrips and mites (Hudson et al. 1985).
From its
overwintering quarters in protected, well-drained places, the flower bug
migrates first to weedy areas in March or April, and then to corn mainly
in the sil king stage of growth (Balduf 1936).
Its immigration into
pean ut fields occurs early in the growing season where its populations
increase about the time peanut plants flower.
Balduf (1936) found
that the peak abundance of both Q. insidiosus and its prey, the corn
earworm, is purely coincidental, and indicated that similarities in
the temporal distribution of both insects in corn may be explained by
their common attraction to certain plant growth stages.
For example,
ovipositing females of both spEcies are attracted to silking corn.
Typically, 4 generations of the flower bugs occur per year.
Populations of Q. insidios1S tire generally limited by the same factors
.
,
that limit populations of Geocoris (Balduf 1936).
Recently, Agnew and Smith (1989) reported that hunting spiders in
the families, Oxyopidae, Lycoposidae, and Thomisidae, comprised 75
1
.'
percent of the spider fauna in peanut in Texas.
OxYopes salticus Hentz,
ï1
Pardosa pauxilla Montgomery, and Misumenops spp. were the dominant
species encountered.
Spider populations generally increased as the
peanut plant canopy increased.
Arthropods in Hemiptera, Lepidoptera,
(Heliothis spp., ~. bosqueella) and other Aranae were the most common
12
prey of the above named spiders, but lE:afhoppers and thrips also were
taken.
Parasitism of insect pests (especially of noctuid larvae) in pean ut
has been more extensively reported than predation in the literature.
The vast majority of insect parasitoids belong to the hymenopterous
families of Ichneumonidae, Sraconidae, and Chalcidoidea, and to the
dipterous family Tachinidae.
Wall and Serberet (1975) reported that as
many as 39 species of parasitoids attack the larvae of 12 lepidopterous
pean ut pests in Oklahoma.
The major parasitic species reported in
peanut by Wall and Serberet (1975) were Pristomerus spinator (F.) and
Apanteles spp., attacking the LCS; Micriplitis croceipes (Cresson) and
Eucelatoria armiqera (Coquillett) attacking ~ zea; and Orqilus
modicus Muesebeck attacking the red-necked peanutworm, Steqasta
bosqueella.
Funderburk et al. (1984) and Leuck and Dupree (1965) also
reported an extensive lists of parasitoids attacking peanut insect
pests in Florida and Georgia, respectively.
.i
1
13
LlTERATURE ClTED
Agnew, C. W., and J. W. Smith, Jr.
1989.
Ecology of spiders (Araneae)
in a peanut agroecosystem.
Environ. Entomol. 18: 30-42.
All, J. N., M. Ali, E. P. Hornizak and J. B. Weaver.
1977.
Joint
action of two pyrethroids with methyl-parathiqn, methomyl, and
chlorpyrifos on Heliothis zea and Heliothis vfrescens in the
laboratory and in cotton and sweetcorn.
J. Econ. Entomol. 70: 813-
817.
All, J. N., R. N. Gallaher and M. O. Jellum.
1979.
Influence of
planting dates, preplanting weed control, irrigation, and
conservation tillage practices on efficacy of planting time
insecticide applications for control of lesser conrnstalk borer in
(
field corn.
J. Econ. Entomol. 72: 265-268.
Arthur, B. W. and F. S. Arant.
1954.
Effect of systemic insecticides
upon certain peanut insects and upon peanuts.
J. Econ. Entomol.
47: 1111-1114.
Arthur, B. W., L. L. Hyche and R. H. Mount.
1959.
Control of the red-
necked peanutworm on peanuts.
J. Econ. Entomol. 52: 468-470.
Atim, A. B. and H. M. Graham.
1984.
Predation of Geocoris punctipes by
Nabis alternaturs.
The Southwest. Entomologist 9(2): 227-231.
Balduf, W. V.
1936.
Orius insidiosus (Say) an important natural enemy
of the corn earworm.
U. S. Oept. Agr. Tech. Bull. 504.
24 p.
Bass, M. H. and F. S. Arant.
1973.
Insect pests, pp. 388-428.
ln Peanuts - Culture and Uses.
Stone Printing Co., Roanoke, Va.
14
Bear, J. E. and W. K. Bailey.
1973.
Earliness of flower opening and
potential for pod development in peanuts, Arachis hypogaea L. J.
Am. Pean ut Res. Educ. Assoc. 5: 26-31.
Beck, E. W., L. H. Dawsey, D. W. Woodham, D. B. Leuck and L. W. Morgan.
1962.
Insecticide residues on peanuts grown in soil treated with
granular aldrin and heptachlor.
J. Econ. Entomol. 55: 953-956.
Belton. W. A.
1953.
Effect of systemic insecticides upon certain
peanut insects and upon peanuts.
Ph.D. Ala. A &M Inst.
(Location?)
Berberet~ R.. C.
1978.
Red-necked peanutworm in dryland peanuts.
1977.
Insecticide and Acaricide Test 3: 132.
Berberet, R. C. and F. Guilavogui.
1980.
Control of red-necked
peanutworm in non-irrigated peanuts.
Insecticide and Acaricide
Test 5: 141.
Bissell, T. L.
1941.
A micro-leafworm on peanuts.
J. Econ. Entomol.
35: 104.
Boote, K. J. and L. C. Hammond.
1981.
Effect of drought on vegetation
and reproductive development of peanut.
Proc. Amer. Peanut Res.
Educ. Soc. 13: 86 (Abstract).
Boote, K. J., J. A. Stansell, A. M. Schubert and J. F. Stone.
1982.
Irrigation, water use, and water relations, pp. 164-205.
ln H. E.
Pattee and C. T. Young (eds.), Peanut Science and Technology.
Am.
Peanut Res. Educ. Soc., Inc., Yoakum, TX.
Campbell, W. V. and D. A. Emery.
1971.
Resistance of peanut accessions
to the potato leafhopper, Empoasca fabae.
J. Amer. Peanut Res.
Educ. Assac. 3(1): 219.
15
Campbell, W. V. and J. C. Wynne.
1985.
Influence of the insect -
resistant, pean ut cultivar NC6 on performance of soil insecticides.
J. Econ. Entomol. 78(1): 113-116.
Cave, R. D. and M. J. Gaylor.
1988.
Parasitism of Geocoris
(Heteroptera: Lygaeidae) eggs by Telenomus reynoldsi (Hymenoptera:
Scelio~idae) and Trichogramma pretiosum (Hymenoptera:P
Tricho~rammatidae) in Alabama.
Environ. Entomol. 17: 945-951.
Chauthani, A. R. and P. L. Adkisson.
1966.
Effect of sublethal doses
of certain insecticides on eggs, larvae, and adults of two species
of Heliothis.
J. Econ. Entomol. 59: 1070-1074.
Cox, F. R.
1978.
Effect of quality of light on the early growth and
development of peanut.
Peanut Sci~ 5: 27-30.
Cox, F. R.
1979.
Effect of temperature treatment on peanut vegetative
and fruit growth.
Peanut Sei. 6: 14-17.
Crocker, R. L. and W. H. Whitcomb.
1980.
Fe~ding niches of the big-
eyed bugs Geocoris bullatus, Geocoris punctipes, and Geocoris
uliginosis (Hemiptera: Lygaeidae: Geocorinae).
Environ. Entomol.
9: 508-513.
Davis, D. L.
1981.
Population dynamics of four species of Geocoris in
the peanut agroecosystem.
Ph.D. Dissertation, Texas A &M. Univ.,
College Station, TX.
Dicke, F. F.
1939.
Seasonal abundance of the corn earworm.
J. Agric.
Res. 59: 237-258.
Ellis, C. R.
1984.
Injury by Empoasca fabae (Homoptera: Cicadellidae)
to peanuts in Southwestern Ontario.
Cano Entomol. 116: 1671-1673.
16
French, J. C.
1971.
The damage and control of the lesser cornstalk
borer, Elasmopalpus lignosellus (Zeller), on ~eanuts and the effect
of soil moisture on its biology.
Ph.D. Diss., Clemson Univ.,
Clemson, SC.
French, J. C.
1973.
Insect pest management on peanuts in Georgia.
Proc. Amer. Peanut Res. Educ. Assoc. 5: 125~127.
Funderburk, J. E., D. G. Bougias, D. C. Herzog, R. K. Sprenkel and R. E.
Lynch.
1984.
Parasitoids and pathogens of larval lesser cornstalk
borer (Lepidoptera: Pyralidae) in North Florida.
Environ. Entomol.
13: 1319-1323.
Geir, P. W. and L. R. Clark.
1970.
An ecological approach to pest
control, pp. 225-233.
ln Pedigo (ed.), Insect Ecology and Pest
Management: Readings in Theory.
Iowa St. Univ. Press, Ames, lA.
Gorbet, D. W. and F. M. Rhoads.
1973.
Response of two pean ut cultivars
to irrigation and kylar.
Agron. J. 67: 373-376.
Gyrisco, G. G., D. Landman, A. C. York, B. J. Irwin and E. J. Armbrust.
1978.
The literature of arthropods associated with alfalfa. IV. A
bibliography of the potato leafhopper, Empoasca fabae (Harris)
(Homoptera: Cicadellidae).
Spec. Publ. 51.
Illinois Univ. Agric.
Exp. Sta.
Hammons, R. O. 1973.
Early history and origin of the peanut, pp. 17-45.
ln Peanut - Culture and Uses.
Am. Peanut Res. Educ. Assoc., Inc.
Stone Printing Co., Roanoke, VA.
684 p.
Hang, A. N.
1978.
light intensity effects on metabolism, growth, and
yield components of peanuts.
Ph.D. Diss. Univ. of Florida,
Gainesville, Fl.
17
Hang, A. N., D. E. McCloud, K. J. Boote, and W. G. Duncan.
1984.
Shade
effects on growth, partitioning, and yield components of peanuts.
Crop Sci. 24: 109-115.
Henning, R. J.
1978.
In a nutshell.
Univ. of Georgia Coop. Ext. Serv.
Leaflet 312.
Herzog, G. A. and J. R. Phillips, Jr.
1987.
The role of chemicals as
adulticides and ovicides against Heliothis species.
Pp. 29-30.
ln
Theory and Tactics of Hel iothis Population Management.
II.
I~secticidal and Insect Growth Regulator Control.
Southern Coop.
Series Bull. No. 329.
Hudson, R., D. Jones and H. Womack.
1985.
Peanut Pest Management
Handbook.
Univ. Georgia Coop. Extension Serv.
57 p.
Huffman, F. R.
1974.
Consumption of pean ut foliage by the bollworm,
Heliothis zea (Boddie) (Lepidoptera: Noctuidae).
M.Sc. Thesis,
Texas A &MUniv., College Station, TX.
Kennedy, G. G., J. R. Young and R. B. Chalfant.
1987.
Efficacyof
chemical insecticides against Heliothis species on corn, lima,
peanuts and tomatoes.
Pp. 17-18.
ln Theory and Tactics of
Heliothis Population Management.
II.
Insecticidal and Insect
Growth Regulator Control.
Southern Coop. Series Bull. No. 329.
Leuck, D. B.
1967.
Lesser cornstalk borer damage to peanut plants.
J.
Econ. Entomol. 60: 1549-1551.
Leuck, D. B. and M. Dupree.
1965.
Parasites of the lesser cornstalk
borer.
J. Econ. Entomol. 58: 779-780.
Lincoln, C., G. Dean, J. R. Phillips, E. J. Matthews and G. S. Nelson.
1966.
Molasses - insecticide sprays for control of bollworm.
i\\rkansas Farrn Res. 15.
4 p.
18
Luginbill, P. and G. G. Ainslie.
1917.
The lesser cornstalk borer.
U.
S. Dep. A.gr. Bull. No. 539.
27 p.
Lynch, R. E.
1984.
Damage and preference of lesser cornstalk borer
(Lepidoptera:
Pyralidae) larvae for peanut pods in different
stages of maturity.
J. Econ. Entomol. 77: 360-363.
Lynch, R. E.} and J. W. Garner.
1980.
Effect of planting date on insect
damage land yield of peanuts.
Am. Peanut Res. Educ. Assoc. 12: 72.
Lynch, R. E., J. W. Garner and L. W. Morgan.
1984.
Influence of
systemic insecticides on thrips damage and vield of Florunner
peanuts in Georgia.
J. Agric. Entomol. 1: 33-42.
Mack, T. P., C. B. Backman and H. W. Smith.
1982.
Why are lesser
cornstalk borer a hot and dry weather pest of Alabama peanuts?
Highlights of Agric. Res. 32: 19.
Mack, T. P., J. W. Smith, Jr. and R. B. Reed.
1987a.
A mathematical
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Ecological Modeling 39: 269-286.
Mack, T. P., R. H. Walker and G. Wehlje.
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Impact of sicklepod
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in Florunner peanuts.
Crop Protection 6: 185-190.
Martin, C. K. and F. R. Cox.
1977.
Effect of water stress at different
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Proc. Am. Peanut Res. Educ.
Assoc. 9: 91.
McGill, J. F.
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Pp. 3-15.
ln
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19
Mitchell, E. R., H. R. Agee and H. M. Taft.
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Control of bollworm
adults on cotton with insecticides.
J. Econ. Entomol. 58: 1030-
1031.
Morgan, L. W.
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Pp. 71-84.
ln Economie Thresholds and Sampling of
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j'
Pallas, J. E., Jr., J. R. Stansell and J. J. Koshe.
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Pedigo, L. P., S. H. Hutchins and L. G. Higley.
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Economie in jury
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20
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Peanut Sci. 12: 64-70.
21
Stern, V. M., R. F. Smith, R. Van Den Bosch and K. S. Hagen.
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Economies of tobacco thrips
/
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l'
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Tappan, W. B. and D. W. Gorbet.
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Effect of irrigation and
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Parasitoids associated with
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Envir. Entomol. 4:
877 -882.
Wall, R. G. and R. C. Berberet.
1979.
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J. Econ. Entomol.
72: 671-673.
Walton, R. R. and R. Matlock.
1959.
A progress report of studies of
the red-necked peanutworm in Oklahoma.
Oklahoma Agr. Exp. Sta.
Prog. Series.
P. 320.
Whitcomb, W. H. and K. Bell.
1964.
Predaceous insects. spiders, and
mites of Arkansas cotton fields.
Arkansas Agr. Exp. Sta. Bull.
690.
22
Wilson, D. M. and R. A. Flowers.
1978.
Unavoidable low level aflatoxin
contamination of peanuts.
J. Am. Oil Chemists Soc. 55: 111A-112A.
Womack, H., J. M. Cheshire, Jr., D. C. Jones, R. E. Lynch and J. W.
Todd.
1988.
Peanut insects.
P. 18.
ln 1986 Summary of Lasses
from Insect Damage and Costs of Control in Georgia.
Ga. Agr. Exp.
Sta. Sp. Publ. No. 46.
/
Wright, F. S., D. M. Porter, N. L. Powell and B. B. Ross.
1986.
(
Irrigation and tillage effects on peanut yield in Virginia.
Peanut
Sci. 13: 89-92.
Young, J. R., E. A. Harrell and W. W. Hare.
1972.
Mortality of adult
corn earworms treated with insëcticidal formulations in sweet corn
in field and in the laboratory.
J. Econ. Entomol. 65: 786-789.
22
Wilson, D. M. and R. A. Flowers.
1978.
Unavoidable low level aflatoxin
contamination of peanuts.
J. Am. ail Chemists Soc. 55: 111A-112A.
Womack, H., J. M. Cheshire, Jr., D. C. Jones, R. E. Lynch and J. W.
Todd.
1988.
Pean ut insects.
P. 18.
ln 1986 Summary of Lasses
from Insect Damage and Costs of Control in Georgia.
Ga. Agr. Exp.
Sta. Sp. Publ. No. ~6.
!
Wright, F. S., D. M. Porter, N. L. Powell and B. B. Ross.
1986.
l'
Irrigation and tillage effects on peanut yield in Virginia.
Peanut
Sci. 13: 89-92.
Young, J. R., E. A. Harrell and W. W. Hare.
1972.
Mortality of adult
corn earworms treated with insecticidal formulations insw~et corn
in field and in the laboratory.
J. Econ. Entomol. 65: 786-789.
III.
COMPARISON OF METHODS FOR SAMPLING INSECTS
ASSOCIATED WITH PEANUT 1
lIdrissa O. Amirou and Robert E. Lynch.
1989.
To be submitted to
J. Environ. Entomol.
23
ABSTRACT
Comparisàns of weekly population estimates of pest and beneficial
insects for whole plant, flower, terminal, and sweep net sampling
/
methods were made in pean ut fields in Tifton, Georgia, during 1986,
!'
1987, 1988.
The number of insects collected by the whole plant method
was surprisingly lower for individual species than the number obtained
by other methods.
Terminal samples or sweep net samples generally
detected peak populations and thus reflected the seasonal trends of
several insect species better than whole plant sampi es.
The termi na l
sampling method also was efficient in sampling small insects such as
immatures and adults of Frankliniella fusca (Hi~ds), larvae of Stegasta
bosqueella (Chambers), and early larval stages of Heliothis zea
(Boddie).
Conversely, the sweep net method yielded a higher number of
larger corn earworm larvae and highly mobile or rapidly flying insects
such as Geocoris spp. and Empoasca fabae (Harris).
A combination of
terminal and sweep net sampling can yield valuable information on the
seasonal trends of most arthropod species commonly encountered in peanut
fields.
In recent years there has been a definite shift from an exclusive
reliance upon a single method for insect pest control to a more
realistic, but complex multitactic, approach to crop protection commonly
referred to as integrated pest management (IPM).
Thi~ change was
/
undoubtably a consequence of the abusive and exclusiv, use of
insecticides as the sole means of pest control following the discovery
of chlorinated insecticides.
As a consequence of this simplistic
approach, much of the scientific base for applied entomology was lost
(Smallman 1970).
Before any suppressive control method is applied, IPM requires
monitoring of insect pest population densities that may lead to
unacceptable crop damage.
Since IPM relies on maximum use of natural
enemies, accurate estimates of beneficial arthropods also is of prime
importance.
However, as Southwood (1978) pointed out, it is normally
impossible to count all arthropods in a habitat.
Thus, it is necessary
to estimate populations by sampling.
Naturally, estimates should have
the highest accuracy commensurate with amount of work expanded.
Samples
that estimate population densities fall into three broad groups:
absolute methods, relative methods, and population indices (Roach et al.
1979).
Morris (1960) argued that sampling based on the absolute unit is
essential, since it provides a common reference point for other sampling
methods.
Morris (1955) enumerated six criteria required for assessing
absolute poplilations:
(1) all units in the universe must have equal
chance of selection; (2) the sample units must be stable and available
25
26
to insects in a continuous manner; (3) the proportion of the insect
population using the unit area must remain constant; (4) the sample unit
should be reasonably small as to allow examination of enough units to
provide an accurate estimate of absolute populations; (5) the sample
unit should provide good estimates; (6) the sample must be easy to
take.
Although absolute samples are essential from an applied viewpoint,
the time and effort required to obtain them are often excessive.
This
may explain why absolute sampling is rarely used in most insect sampling
programs.
In contrast, IPM decisions are frequently based on rapidly
obtained population estimates based on relative methods (Fleischer et
al. 1985).
The extensive use of relative methods also stems from the
fact that while absolute methods of sampling are seldom 100% efficient,
relative methods can be corrected in various ways to give accu rate
density estimates (Southwood 1978).
Various methods have been used to sample arthropod populations in
peanut fields.
The most frequently used techniques include shake and
beat samples, sweep net samples, direct field observations and counts,
and samples of plant structures such as terminals or flowers.
These
methods have been used primarily because they are inexpensive and
.1
/provide easily obtained estimates of populations.
Although, llttle
attention has been given to the comparative efficiency of these sampling
, methods for estimating populations of insects associated with peanut,
several studies have shown their utility in estimating insect
populations associated with cotton and soybean (Shepard et al. 1974,
Smith et al. 1976, Ellington et al. 1984) .
.. \\
".
1ë'"
27
Linker et al. (1984) compared the sweep net and shake cloth methods
for sampling insects associated with peanut.
They reported that the
shake and sweep estimates were not as consistent for estimating
populations of corn earworm larvae as they were for the fall armyvJorm.
Davis (1981) used a direct observation method and aspirators to
concurrently determine the density of lesser cornstalk borer larvae
and e9g and fi l'st nymphal i nstars of the bi g-eyed bug.
However, the
efficiencies of the two methods were not compared.
Thus, few studies
have attempted to compare efficiencies of sampling methods in estimating
populations of pest and beneficial insects on peanut.
The objective of the present study was to compare the efficiencies
of three sampling methods commonly used to evaluate populations of pest
and beneficial species found on peanut.
The efficiencies of these
methods also were compared with the efficiency of the whole plant
sampling method, an absolute sample.
Materials and Methods
..
The studies were conducted on the Bellflower Farm, near the Coast al
Plain Experiment Station, Tifton, Georgia, during the summer of 1986,
1987, and 1988.
Plots were planted with Florunner peanuts, Arachis
hypogaea L., on May 19, 1986, June 4, 1987, and
June 2, 1988, on 1.62
hectares. Standard production practices were followed each year, except
that insecticides and irrigation were not applied. The survey fields
were subdivided into five equal plots in 1986 and into six equal plots
in 1987 and 1988.
Five weekly samples were taken from each plot on
randomly chosen rows using the whole plant, flower, terminal, and sweep
28
net sampling techniques.
Samples were collected from ca. 7-11 a m. on
each sampling date.
A detailed description of these methods is given below.
Whole plant method.
A randomly selected area of 0.50 m of row was
delimited using an area sampler.
The area sampler was made of sheet
metal with dimensions of 0.50 m x 0.30 m x 0.20 m, and with both ends
open.
Plants from each 0.50 m row were quickly pulled and placed in
labeled plastic bags.
After plant removal, the soil surface was also
searched for insects which were placed in the bags along with the
plants.
All bags were then transported to the laboratory where plants
were counted and processed to remove insects.
Plants were processed by
submerging them in 1.0% sodium hypochlorite solution in a 18.9-1 plastic
container and agitating them for ca. 5-10 minutes.
Plants were then
removed from the solution, held above the containers, and thoroughly
rinsed with water to dislodge insects that remained on the plant
toliage.
The wash solution was then poured through a series of 10, 20,
and 100-mesh sieves.
The 100-mesh sieves containing insects were back
washed into 100 ml plastic cups.
Insects on the 10 and 20 mesh-sieves
were removed and also placed in the plastic cup.
Cup contents were
poured into petri dishes and insects were identified and counted using a
dissecting microscope.
,1
Terminal method.
Ten unopene~ peanut terminals were collected at
random from 0.50-m row as described above, and placed in 118-ml capped
plastic containers with ca. 50ml of 70% ethanol.
The containers were
then capped , agitated for ca. 1 min., and carried back to the
laboratory where their contents were emptied into petri dishes and the
insects were counted under magnification.
29
Flol'iPI- method.
Each flOl'icr sël;,iple consisted of la flOl·vers
lo11ected and processed as described above for terminals. ln addition,
the total number of flowers within each 0.50 m row was counted and
recorded. The number of flowers / 0.50 m of row was determined only in
1987 and 1988.
Sweep net method.
Sweep samples were taken with a 38 cm net
as the investigator walked along the pean ut row.
ln 1986, each sample
consisted of 10 pendular sweeps, which was increased to 25 sweeps in
1987 and 1988.
lnsects were transferred from the sweep net to labelled
3.8 l sealable plastic bags and taken to the laboratory for identifi-
cation and counting.
Sweep net samples were initiated when plant were
ca. 10 cm in height and were generally made ca. 9 a m. after dew had
evaporated fro~ foliage.
The numbe l' of insects collected in the sweep net was converted to
number of insects/10 plants in 1986 and to number of insects/25 plants
in 1987 and 1988 using the conversion procedure proposed by Byerly et
al. (1978) al)d Wilson and Gutierrez (1980) as follows:
C = 1 / dia'. in
m of net x nllmber plants / m-row
where C is the conversion factor to
plant values.
The number of insects from whole plant estimates also was converted
.1
to the number of insects / 10 plants in 1986 or ryumber of insects / 25
plants in 1987 and 1988.
The numbers of insects from flowers also was
converted to the number of insects / 25 plants.' S-ince the number of
terminals per unit area was not recorded in any of the three years, the
number of insects from terminals could not be ~onverted to number / plant
value.
Therefore, estimates for insect numbers in terminals are
30
inc1uded on1y for graphica1 comparisons with estimates by whole plant,
f10wer, and sweep net methods.
Insect identification was confirmed for most species by Dr. Cecil
Smith, curator at the University of Georgia's Museum of Natura1 History.
Thrips species were identified by Mrs. Ramona Beshear, Georgia
Experiment Station, Griffin, Georgia.
Parasite specimens were
identified by Dr. Henry Townes, American Entomo10gica1 Institute,
Gainesvi11e, F10rida.
Univariate analyses were conducted on the number of insects
co11ected in week1y survey to determine the frequency distributions for
the species co11ected.
The number of insects co11ected for most species
was not norma11y distributed.
Therefore, insect data were transformed
to log (x+l) to stabilize the variance.
Transformed data th en were
ana1yzed by ana1ysis of variance and week1y means were separ2ted using
Wa11er-Duncan's multiple range test (Waller and Duncan 1969),
Statistical analyses are presented on1y for the 1988 data, since they are
.- representative of the 3-year study.
Results and Discussion
Samp1es were co11ected on nine dates in 1986, 10 dates in 1987, and
Il dates in 1988 (Table 3-1).
During the 3~ year study, insects from Il
arthropod orders, representing Il fami1ies of pest species, 10 fami1ies
of predaceous arthropods, and two fami1ies of parasitic Hymenoptera were
co11ected from peanut.
Lists of the arthropod species or groups and the
frequency at which each species was co11ected / method each year are
shown in Table 3-2 through 3-4 (Appendix).
Severa1 arthropods species
were represented on1y by few specimens on most sampling dates, and many
3]
were not collected on sorne sampling dates.
Therefore, only pest and
beneficial insect species or genera that were collected regularly from
peanut plants by at least two sampling methods will be discussed
further.
Regularly collected species include : (1) immature and adult
thrips, Frankliniella fusca (Hinds); (2) larvae of corn earworm,
Heliothis zea (Boddie) (3) larvae of rednecked peanutworm, Stegasta
bosqueella (Chambers); and (4) nymphs and adult potato leafhopper,
Empoasca fabae (Harris).
Also included are nymphs and adults of two
hemipteran predator groups, Geocoris spp. and Orius insidiosus (Say).
Insect pest soecies
Frankliniella fusca.
The seasonal population trends for thrips
established by the whole plant and terminal sampling methods ~vere quite
similar, with both methods detecting increases in immature thrips
densities on the same dates (Figs. 3-1 and 3-2). Thus, eiiher method
could be used to adequately monitor seasonal trends for the t~bacco
thrips in the field.
However, the whole plant method require~ a greater
number of man-hours to collect and process samples than is raquired for
the terminal method.
Thus, it is likely that the termin~l mèthod will
remain the preferred sampling technique for estimating densities and
establishing seasonal trends for populations of immature [. fusca in
peanut.
Statistical comparisons between the numbers of immature
tobacco thrips collected by the flower and whole plant methods in 1988
are shown in Table 3-5.
Except on the first sampling date, population
estimates by the flower method were either significantly higher or
statistically comparable with whole plant estimates in 1988.
Hence
the flower method, which is comparable to the terminal method in the
32
ease and time required to collect and process samples, could be used
in lieu of terminal sampling method for estimating thrips populations
'in peanut.
Except in 1987 when the whole plant method failed to
detect peak populations, the seasonal trends for adult f. fusca
established by whole plant, terminal, and flower sampling methods
generally mimicked populations observed for immature thrips (Figs. 3-3
and 3-4).
However, populations of adult thrips fluctuated more widely
than populations of immatures.
These fluctuations may have been
partially caused by adult mobility.
Lewis (1973) found that even a
slight disturbance of the thrips habitat caused adults to fly away.
Thus, many adults may have been lost in handling and processing of
whole plant samples.
Tappan (1986) observed that number of adults in
flowers varied with the time of day the samples were taken.
Therefore, it is likely that all methods underestimated populations of
adult thrips.
Empoasca fabae.
Several peak populations were detected by the
terminal and sweep net"sampling methods, but none was detected by the
whole plant method in 1986, 1987, and 1988 (Figs. 3-5 and 3-6).
The
number of leafhoppers / 25 plants was significantly low~~ for the whole
plant than the number for the sweep net method.
Conversely, the
,/
coefficients of variation yielded by the whole plant were much greater
,
than coefficients obtained by the sweep net method (Table 3-5).
Consequently, the sweep net gave more reliable estimates of leafhopper
populations than the whole plant method.
The marked tendency of both nymphs and adults of the potato
leafhopper to jump, run, or fly when disturbed (Metcalf et al. 1962)
probably accounted for the low population estimates obtained by the
33
whole plant sampling mcthod.
Similarly, the sweep net method probably
underestimated leafhopper populations, despite the relatively higher
mean densities indicated by this method.
Delong (1932) reported that
many adult leafhoppers escape capture by sweep net because they
readily leave the plants upon detecting movement by an approaching
investigator.
Simonet et al. (1978) also found that nymphs become
entangled in the net, thus reducing the efficiency of the sweep net
method for sampling leafhoppers.
These and other factors, such as
decreasing catch size with increasing plant vegetative growth (Cherry
et al. 1977), also may reduce the efficiency of the sweep net sampling
method.
Although the population trends established for the potato leaf-
hopper by the terminal sampling method were similar to the trends shown
by the sweep net method, it is doubtful that the low density estimates
obtained with the terminal method could be used accurately to predict
seasonal population fluctuations (Figs. 3-5 and 3-6).
Heliothis zea.
80th the terminal and sweëp net sampling
methods detected clear population peaks in 1986, 1987, and 1988 for H.
zea (Figs 3-7 and 3-8).
Although no population trends were established
for H. zea by the whole plant method, slight population fluctuations
,1
were observed in 1986.
1
Early in the growing season the terminal sampling method
consistently detected peak populations of H. zea larvae at
least 2-3 weeks earlier than they were detected by the sweep net method.
Differences in population ~stimates between the two sampling methods
reflect the feeding behavior of first- and second-instar corn earworm
larvae, which feed almost exclusively between the folded leaves of
34
pean ut terminals during the early growing season (tlorgan 1979).
Older
larvae, up to third instars, also prefer terminals, but are exposed on
the plants rather than hidden in the terminal leaflets.
However, as
peanut plants enter the rapid vegetative growth phase beginning 40-50
days after planting (Table 3-1), terminals unfold at an accelerated
rate exposing small larvae that migrate to another terminal or flower.
Thus, as the season progresses, more larvae are exposed and the
efficiency of sweep net sampling is increased.
This is evidenced by
the small difference between the number of insects collected by the
two sampling methods and in their ability to detect peak populations
of the corn earworm as the growing season progressed (Figs. 3-7 and 3-
8).
These data supoort a report by Linker et al. (1984) that the
efficiency of the sweep net sampling method increases as H. zea larvae
grow larger and shift from feeding in terminals to feeding on fully
developed peanut leaves.
A significijntly higher number of corn earworm larvae was collected
by the sweep ne~ s~mpling method than the whole plant sampling method
(Table 3-5).
Two main reasons probably accounted for the greater
efficiency of the sweep net sampling method:
(1) despite all efforts
that were made to search and collect larvae dislodged ]n the field as
the plants were pulled and bagged, many of the larvae ~scape to adjacent
plants; and (2) as the number of terminals increased, it became
difficult to wash larvae out of plant foliage.
Peanut plants were
notably smaller in 1986 due to a dryer growing season th an in 1987 or
1988 which probably explains why relatively more laryae were recovered
by the whole plant method in 1986 th an in 1987 or 1988 (Figs. 3-7 and 3-
8).
35
Stegasta bosqueella.
Although whole plant, terminal, and
sweep net sampling methods detected some level of ~. bosqueella larval
populations each year, relatively greater densities were estimated by
the whole plant and terminal methods sampling (Figs.3-9 and 3-10).
Red-necked peanutworm larvae feed exclusively in terminals (Arthur et
al. 1959, Wall and Berberet 1979).
Thus, the sweep net was
inefficient in sampling this insect as can be noted by significantly
fewer
individuals collected with the sweep net than with the whole
plant method (Table 3-5).
In two of the three years, i.e. 1987 and 1988, increases in larval
populations of ~. bosqueella
were detected earlier by the terminal
sampling method than with the whole plant method (Figs. 3-9 and 3-10).
Bissell (1941) and Walton and Matlock (1559) reported that peak
populations of ~. bosqueella larvae generally occur 50-90 days after
peanut .is planted, i.e. during the period of maximum terminal produc-
tion.
With the exception of the ter~inal sampling in 1986, both the
terminal and whole plant methods detected increases in ~. bosqueella
populations during this critical period. Predaceous insect species
Ge6coris spp.
Big-eyed bugs, Geocoris spp., are shown to be
important predators of several insect pest species in various cropping
systems, including'cotton (Kinzer et al. 1977), soybean (Shepard and
Carner 1974), tobacco (Semtner 1979), corn (Harrison 1959), and peanut
(Davis 1979).
As shown in Figure 3-11 and 3-12, the whole plant method
failed to detect peak populations of nymph and adult Geocoris as quickly
as the sweep net.
Similarly, the number of Geocoris collected was
significantly lower for the whole plant in seven of the eight sampling
dates in 1988 than were colleced by the sweep net method (Table 3-5).
-\\
.-
36
Geocoris nymphs caught by the sweep net and whole plant sanlpling
methods represented similar proportions, ca. 0.20% of overall arthropods
collected by each method (Table 3-4, Appendix).
Adult big-eyed bugs,
,
however, made up a greater proportion of arthropods collected by sweep
net than by the whole plant method.
This suggests that the poorer
performance of the whole plant sampling method was due to the mobility
of adults, which allowed many individuals to escape during handling
and processing of samples.
Gonzalez and Leigh (1982) found that
mobility of Geocoris adults lead ta loss of a significant number of
individuals when populations were sampled on cotton by either visual
or Berlese methods.
Despite the significantly higher estimates of
adult densities obtained, the sweep net method may still have
underestimated population levels since adults are primarily soi1-
dwellers (Davis 1981).
Orius insidiosus.
Although whole plant, flower, terminal,
and sweep net sampling methods detected increases in Q. insidiosus
populations, the seasonal trends which each method establishedvaried
greatly within years (Figs. 3-13 and 3-14).
The variability in popula-
tion estimates of Q. insidiosus could be partially explained by the fact
that while the whole plant, flower, and terminal methods were more
efficient in collecting the nymphal stages of the flower bug, the sweep
net method appeared to be more efficient in estimating adult densities
(Table 3-2 through 3-4, Appendix). Overall, the terminal method and
whole plant method provided the best estimates of population trends for
~ insidiosus.
Combined totals for the number of the immature and adult flower
bugs obtained were significantly higher by the whole plant method than
37
estimates by flower or sweep net methods on most dates when samples were
taken by all three methods (Table 3-5).
On remaining sampling dates,
however, estimates by the whole plant method were either nonsignificant
or significantly lower than estimates obtained by other sampling
methods, illustrating major discrepancies in sampling that may be
observed with all methods, e.g., inconsistency in recovery of
individual Q. insidiosus.
Dumas et al. (1964) reported that
environmental factors, e.g., air temperature, time of day, and cloud
coyer, affect population estimates obtained
with the sweep sampling.
Conclusions
Surprisingly, the whole plant method collected fewer arthropods
than expected, probably due to appreciable loss of mobile insects during
plant handling and processing.
The efficiency of this sampling method
also probably decreases as the quantity of peanut foliage increases.
The relative inefficiency of the whole plant sampling method and the
relatively greater number of man-hours required for its use are likely
to render this method unattractive for most peanut insect investigations.
Comparisons of the other sampling methods revealed thal differences
among methods to detect peak insect populations is probably related to
,1
the biology and/or behavior of a particular species.
The early larval .
!
stages ot ~. zea and practically all larval stages of ~. bosqueella feed
and dev~lop within peanut terminals.
Thus, the seasonal trends of these
two insect species are more adequately established by the terminal
sampling method than sweep net method.
Conversely, highly mobile or
rapidly flying insects, such as predators or adult pest species, are
likely to be more efficiently sampled by the sweep net than by terminal
38
or flower sampling methods.
The whole plant method adequately estimated
population trends for several of the less mobile insects, but, due to
costs required for collecting and processing whole plant samples, it is
not a viable method for establishing population trends for insects of
peanut. Thus, no one sampling method alone may be expected to suitably
estimate populations of all stag~s and species of peanut arthropods.
One of the weaknesses of re1ative sampling methods, like those
investigated in this study, is that they sample an unknown portion of
arthropod populations (Southwood 1978).
However, it appears from thrse
results that a combination of terminal and sweep net sampling method~
can yield valuable information on the seasonal trends for many
arthropods found in peanut fields.
Conversion of data from a combi~a
tion of methods to a more quantitative form, i.e. plant basis or row
basis, will probably provide more reliable information than beat and
shake methods that are now the most widely used sampling methods
for estimating populations of insects in peanut.
39
,
/
/'
Figure 3-1.
Population estimates for immature thrips,
Frankliniella fusca (Hinds), in peanut ai Tifton, GA, determined by
three sampling methods in 1986-1987.
40
YEAR=86
500
26
CI)
0+-
C
o
a-
0
400
L-
a>
a-
CI)
\\
0..300
'L:
..c
.-
\\
1.3
L-
a>
\\,
,
,~--~
L-
iU
:J
\\ /
\\,
a.
.
1; 200
~/
o
E
\\',
z
E
\\
.
c
~-
o
Q)
o
~--
z
~
100
c
'---'---
o
a>
~
o
0
l.3JUN
23JUN
03JUL
13JUL
2.3JUL
02AUG
12AUG
22AUG
01 SEP
Date
YEAR=87
CI) 1500
60
......
c
o
a-
l/)
N
L-
Q)
~ 1000
a.
'L:
,
..c
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o
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o
E 500
20 z
c
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o
~
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o
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~
O~~~~......~~-'-'-'~~~~~~~.....-r~~~-T~~"""""'~-r"""""~";"""'''''''''''''''
o
2BJUN
OBJUL
lBJUL
2BJUL
07AUG
17AUG
27AUG
06SEP
Plants
~
F10wars
@---E)
Nat
[ 3 - - 0
TarmlnQ/s
<)----0
41
/
"
Figure 3-2.
Population estimates for immature thrips,
Frankliniella fusca (Hinds), in peanut at Tifton, GA, determined by
three sampling methods in 1988.
N
<::t
YEAR=88
CI) 700 ~
G>
rSO
-c0-a...
\\
lt1
CI)
\\
-
"'"
0
L
45 c
CD
0 -
a...
E
1...
CI)
<D
Q..
1-
"L
0
..c
..--
1- 350
30
1...
CD
CD
L
~
Q.
-
0
0
0
E
z
E
c
15 0
0
)
'~~
(1)
0
f
~
Z
.
--
~
-- .
c
~
~
,
0
ra~/
'--€>
CD
:L
0
0
12JUN
22JUN
02JUL
12JUL
22JUL
01AUG
11 AUG
21AUG
31AUG
10SEP
Plants
)(
)(
Flowers
8-----E)
Net
G---E1
TerminaIs
<r--'~
43
/
l'
Figure 3-3.
Population estimates for adult thrips, Frankliniella
fusca (Hinds), in peanut at Tifton, GA, determined by three sampling
methods
in 1986-1987.
44
YEAR=86
120
2.5
.'>
/'
lIJ
-c
/"
o
/,'
a...
lIJ
1/"
o
o
/'
c
/
~ 80
- ..(5"
2.0
E
L-
l'
a...
a>
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lIJ
a.
o
'c
..t:
"-
J-
II)
=
a.
.
:l
o
-0
« 40
1,5 zc
o
o
z
~
c
~
o
a>
~
o
~o
13JUN
23JUN
03JUl
13JUL
23JUl
02AUG
12AUG
22AUG
01 SEP
Date
YEAR=87
1100
lIJ
-c
!
5
o
a...
lIJ
1()
825
4 g
N
---e
L-
a>
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a...
G)
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lIJ
a.
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~ 550
3
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=
a.
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:l
o
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c
o
275
2 0
Z
~
c
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o
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~
o'r-..-~~~....-~~~rro-~~~~~~~~rro-~~~~~~~~~,..o...~.-I1
2BJUN
08JUl
1BJUL
2BJUl
07AUG
17AUG
27 AUG
OSSEP
Plants
~
F10wars
@---E)
Nat
8--0
TermInaIs
<)-~
45
Figur03-4.
Population estimates for adult thrips, Frankliniella
fusca hHnd~), in pean ut at Tifton, GA, determined by three sampling
method3 in 1988.
YEAR=88
150
4
li)
(i)
.
-
\\
1 \\
c
1
\\
o
•
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1
\\
CL
\\
1
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CIl
•
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1
\\
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l.()
1
,
\\
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3
c
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100
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L
CL
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l -
li)
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50
,
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0
1
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1
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1
0
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Q)
c
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0
Q)
:::E
o~i
r
i '
i
1
i '
1
i
i
i
/.......
i
0
12JUN
22JUN
02JUL
12JUL
22JUL
01AUG
11AUG
21AUG
31AUG
10SEP
Plants
X
>(
Flowers
G-----E)
Net
G---E]
Terminais
<r--'~
- . ,
" " - - < '
+:-
Q)
47
,
/
"
Figure 3-5.
Combined population estimates for nymphal and adult
potato leafhopper, Empoasca fabae (Harris), in peanut at Tifton, GA,
determined by three sampling methods in 1986-1987.
48
YEAR==86
90
~
0.2
1 \\
.. ,
1 "
r:1
..
,
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1
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n.
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l -
1
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i \\
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l
...J
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Z
c
f'
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t
o
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II)
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II)
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1
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l ' :
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o
0.0
13JUN
23JUN
03JUL
13JUL
23JUL
02AUG
12AUG
22AUG
01 SEP
Date
YEAR==87
400
0.15
~
li)
/ \\
:=
. ,
li)
n.
i.
",
o
~300
c
i
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E
0.10
l -
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II)
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a.
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.
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oUt::::::::;:::;~:;:::;::;*::;::::;:::;:;::;};i~:':::~~~....-ro-':':-,=~:t:;;;::;::;:::;~;::::::~~-JO.OO
28JUN
08JUL
18JUL
28JUL
07AUG
17AUG
27AUG
06SEP
Plants
>f---X
f"lowers
@ - --8
Net
[3--0
Terminais
<)---<)
49
,
/
l'
Figure 3-6.
Combined population estimates for nymphal and adult
potato leafhopper, Empoasca fabae (Harris),
in peanut at Tifton, GA,
determined by three sampling methods in 1988.
YEAR=88
180
~
0.08
J
\\
/
\\
J
\\
li)
-
/
J
\\
a..
A
li)
r;;;l.
/
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-
/
0
L() 135
"
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0.06
c
N
.-
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/ \\
/
\\ ~
E
/
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li)
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~
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(l)
(l)
/
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1
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c..
.
;'
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0
~
....-
90
-
1
\\. /
\\
0.04
~
(l)
o
.
~/
\\
c..
(l)
.
- l.
f \\
If?\\
\\
0
o
Z
Z
/
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1 / \\
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c
c
45
0.02
0
o
/
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(l)
(l)
-1/
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2
::E
/
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tJ
O-l
3lf
)t:::
<?
7'
7'1;
-
X
0
/"
A
1- 0 00
i
1
l '
I
i
i
'
i
i l .
12JUN
22JUN
02JUL
12JUL
22JUL
01AUG
11AUG
21AUG
31AUG
10SEP
Plants
)(
x
Flowers
0-----8
Net
G----EJ
Terminais
<7--'~
Ul
a
51
/
r
Figure 3-7.
Estimates
for corn earworm, Heliothis zea
(Boddie)
in peanut at Tifton, Ga, determined by three sampling methods in 1986-
1987.
52
YEAR=86
15
!\\
1.00
Ci)
.....
/ \\
c
.!!
o
0.75
0
c
a-
i
\\
a 10
E
1
\\
....
<D
\\
t-
a
\\
0.50
....
<D
\\
0.
o
d
z 5
z
c
f i - - - _
\\
c
o
Î\\1
o
"
----lif:;1
0.25
4)
4)
~
~
~---
o
0.00
13JUN
23JUN
03JUL
13JUL
23JUL
02AUG
12AUG
22AUG
01 SEP
Date
YEAR=87
240
0.8
~
?
,---8
1
\\
Ci)
!?
c
l' /'\\
o
..2 180
0.6
c
a-
E
10
....
QI
N
t-
....
4)
a-
/ i \\\\
a
~ 120
0.4 ....
<D
w
0.
<.>
o
j
'\\ "
o
z
za 60
4)
/~-- !\\ \\
c
0.2
g
~
:JE
1
l
'........
\\
/
1
l " '0 \\.
1
<)----
/
.-'
oWf:=~~:;::;::;~~~~::;::;::;~t:;::;.~~
...........~~~~~~ ...................~~-Jo.O
28JUN
08JUL
18JUL
28JUL
07AUG
17AUG
27AUG
06SEP
Plants
x----x
f10wers
e - --8
Net
( ] - - Q
TermInais
~-~
'----~._-------_.
53
/
Figure 3-8.
Estimates for corn earworm, Heliothis zea
(Boddie),
larval population in peanut at Tifton, GA, deterrnined by three sampling
methods in 1988.
---- ..
YEAR=88
110
0.8
o
~
(1)
0+-
/
/'
1
\\
(1)
C
. ~
/ \\
o
o
0.6
c
0..
/1\\
! \\
.-
E
Li")
~
1/ \\
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\\
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,: \\.
.1 /
\\
/
\\
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(0
~
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1 \\ / 1
\\
1
1
(0
/ '
/
\\
\\
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1
\\
1
1
o
0..
.
. /
/
\\
\\
....-
3= 55
1
0.4
~
(0
w
\\j ;1
~
;
\\
Q.
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1
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1
.
.
/
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1
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1
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o
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1
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tJ
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0 -1
) f
~ c
X
~-
-
~
1-0 0
1
i
i
i
1
i '
i
i
i
•
12JUN
22JUN
02JUL
12JUL
22JUL
01AUG
11AUG
21AUG
31AUG
10SEP
Plants
)<
X
Flowers
(3-----E)
Net
G---EJ
Terminais
<r--'~
lJ1
+::>
55
Figure 3-9.
Estimates for red-necked peanutworm, Stegasta
bosgueella (Chamb.), larval populations in peanut at Tifton, GA,
obtained by three sampling methods in 1986-1987.
~.
-- ,--
56
YEAR=86
4
30
lIJ
lIJ
3
-c
0
c
o
~ 20
E
L..
a
II)
1-
a
2 L..
II)
a.
o
o
Z
z 10
c
c
o
o
II)
II)
~
~
o
0
13JUN
23JUN
03JUL
13JUL
23JUL
02AUG
12AUG
22AUG
01SEP
Date
YEAR=87
18
0.2
1\\
l "'-,
i
''-,
lI'I
lI'I
+-
C
/
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c
o
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E
L..
L() 12
II)
N
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L..
a
II)
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0.1
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a.
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o
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6
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/
c
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II)
II)
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1
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/
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'21
l"
M----.=::~ ,
o Wr.;::~~::"""...........~,......-:":-'-:::::~l:;..:;::;::;..:;a~~~..,...,..,. ...........~~~~~....--.--t 0.0
28JUN
08JUL
18JUL
28JUL
07AUG
17AUG
27AUG
06SEP
Plants
~
Flowers
e - --8
Nat
13-iJ
TermInaIs
<)-~
57
/
r
Figure 3-10.
Estimates for red-necked peanutworm, Stegasta
bosqueella (Chamb.), larval populations in peanut at lifton, GA,
determined by three sampling methods in 1988.
YEAR=88
60
0.25
r'\\
li)
\\
.
0.20 ~
-c
1
.
o
045
c
.
\\
a..
E
1
.
l.-
liJ
a.>
.
N
\\
0.15 r-
l.-
1
.
a.>
a
a..
\\
.
.,......
_30
l.-
1
.
z
a.>
0::::
\\
.
0.
.
1
.
0.10
.
o
o
.
\\
z
Z
1
.
c
c
015
o
a.>
a.>
~.
1
\\
0.05 2
2
/
"'"
.
/
,,1
.
1
ol ,1. )( . ~-I~---P'
X
1
l '
l
,0
Jo.oo
12JUN
22JUN
02JUL
12JUL
22JUL
01AUG
11AUG
21AUG
31AUG
10SEP
Plants
)(
)(
FI owe rs
(3-----€)
Net
G---EJ
Terminais
O---'~
U'1
co
.... -
~
59
Figure 3-11.
Population estimates for nymphs and adults of
Geocoris spp., in peanut at Tifton, GA, determined by two sampling
methods in 1986-1987.
60
YEAR=86
3
1/)
::
0-
o
~2
rn
:J
al
-0
II)
>-
,~
w
1 \\
rn
i
\\
,
\\
ID
/
\\
<> 1
.-
~
/
\\
1
\\
1
\\
~
\\
/
\\
/
\\
,/'
\\
O\\-.-.~~=r=;=;::;::;::;;::;:::;5I;:;:;;=;=;=,*=;::::;:::;:::;:::?:(=~iIII;::;:=~::;::::;:::;:~;;::;::;:::;::::;:::;:~~ .....................,,......,...,~~
13JUN
23JUN
03JUL
13JUL
23JUL
02AUG
12AUG
22AUG
01SEP
Date
YEAR=87
40
en
::
0-
~30
""'-
en
rn
:J
al
-0
~20
w
rn
ID
\\
o
z 10
c
o
II)
~
) (
1
>S. •
,);(••..• lE 1 \\
o
•
,)f~
28JUN
08JUL
07AUG
17AUG
27AUG
06SEP
Pla n ts
)f--------)(
F10wers
e - --El
Net
G--{]
...
----J
_ ~
~ . .-
61
i
/'
Figure 3-12. Population estimates for nymphs and adults of Geocoris
spp., in peanut at lifton, GA, determined by two sampling methods in
1988.
YEAR=88
28
~
I"
/
\\
,
1
CIl
/
\\
-
0-
1
1
,
\\
lt)
1
·
N 21
,
~
\\
1
1
CIl
/
\\
,
1
0>
:J
,/
--.
\\
CD
/
, , - - , , '
-0
,
\\
/
1
~ 14
,
\\
w
/
.
,
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0>
/
1
.-
CD
,
\\
/
1
.
o
1
\\
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7
c
o
n'~
\\
(l)
j
' /0-_ --
'/
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2
,
X
.-21/----8
,)(
)(
CJ
O
12JUN
, t . '
)(
l'r-
~
i
) (
i -
'
) (
i
) (
\\
22JUN
>,<
)(
i
i
02JUL
i
i
12JUL
~1.JUL
01AUG
11AUG
21AUG
31AUG
10SEP
Plants
x
)(
Flowers
G-----€)
Net. C3----EJ
Cl'>
N
63
/
r
Figure 3-13.
Population estimates_ for nymphs and adults of Orius
insidiosus (Say), in peanut at Tifton, GA, determined by four sampling
methods in 1986-1987.
64
1/1
:!:: 20
a-
LO
N
":-
e> 15
(1)
:::>
0::
~ 10
o
z
c
o
G)
5
~
Plants
>f---X
Flowers
<3 - --El
Nat
"
- - - - J
65
/
l'
Figure 3-14.
Population estimates for nymphs and adults of Orius
insidiosus (Say), in peanut at Tifton, GA, determined by four sampling
methods in 1988.
YEAR=88
5'
0.5
CI)
=4
0.4 ~
0...
o
c
11')
N
E
"'-.
~
Q)
0...3
0.3 1-
V>
o
V>
.....-
~
~
0:::
Q)
Cl..
°2
0.2
.
.
o
o
Z
Z
c
c
o
.........- ,",'
o
. Q )
Q) 1
o.r 2
2
, .f G,,
1
,,,,,,
0 1,
)<
f
~
i
i
0 ,
[?-;--
~
~-
-=;=P
,-
-
~ -;=EJ
,~O.O
12JUN
22JUN
02JUL
12JUL
22JUL
01AUG
11AUG
21AUG
31AUG
10SEP
Plants
)(
)(
Flowers
G-----E)
Net
G----EJ
TerminaIs
~'-.e>
0 )
0 )
67
Table 3-1.
Schedule of sampling dates for estimating arthropod
populations in pean ut ~t Tifton, Ga., 1986-1988.
;
1986
/
1987
1988
l'
Sampling
Days since
Sampling
Days since
Sampling
Days since
date
planting
date
planting
date
planting
6/19
30
6/30
26
6/20
18
6130
41
7/07
33
6/27
25
7/07
48
7/14
40
6/05
32
7/14
55
7/21
47
7/12
39
7/21
62
7/28
54
7/18
45
7/28
69
8/04
61
7/25
52
8/04
76
8/11
68
8/02
59
8/11
83
8/18
75
8/08
65
8/25
97
8/25
82
8/18
75
9/01
88
8/29
86
9/07
94
68
Table 3-5.
Mean population density for insects in pean ut at Tiftan, Ga.,
as obtained with four sampling methods, 1988.
Sampling
Insect
Sampling
Xl
CV 2
date
status
Insect species/group
technique
)
7/12
Pests
Thysanoptera: Thripidae
/
Frankliniella fusca
(Hinds)
l'
immatures
Whole Plant
208.47a
45.90
Flower
38.34b
77 .30
Termi na1
15.5Q,
66.53
adults
Whole Plant
33.77a
73.48
Flower
28.33a
76.20
Termi na1
2.33
73.23
Lepi doptera: rioctu idae
Heliothis zea (Boddie)
1arvae
Whole Plant
1. 74à
181. 87
Flower
0.60a
Sweep net
o.14a 223.61
Termi na1
0.17
318.40
Lepidoptera: Gelechiidae
Steqast~ bosgueella
(Chamb.)
larvae
Whole Plant
0.27a
223.60
Flower
O.OOa
Sweep net
O.OOa
Termi na1
0.00
Homoptera: Cicadellidae
Empoasca labae (Harris)
nymphs
Whole Plant
3.01a
128.04
+
adults
Sweep net
18.44b
72.55
Terminal
0.00
Predators
Hemiptera: Lygaeidae
Geocoris spp.
nymphs
Whole Plant
O.OOa
+
adults
Sweep net
0.95a
170.10
Termi na1
69
Table 3-5. (cont'd)
Sampling
Insect
Sampling
date
status
Insect species/group
techniques
cv
Hemiptera: Anthocoridae
Orius "insidiosus (Say)
nymphs
Whole Pl ant
4.98a
9.36
+
adults
Flower
0.91b
24.33
Sweep net
4.63a
Termi na l
0.50
267.49
"
7/18
Pests
Thysanoptera: Thripidae
Frankliniella fusca
(Hinds)
immatures
Whole Plant
188.41a
54.80
Flower
106.91a
57.93
Termi nal
7.53
60.95
adults
Whole Plant
33.41a
82.82
Flower
138.21b
67.04
Terminal
0.83
122.39
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
larvae
Whole Plant
7.45a
142.20
Flower
2.00b
Sweep net
2.79b
142.58
Terminal
0.57
158.41
Lepidoptera: Gelechiidae
Stegasta bosqueella
(Chamb.)
l arvae
Whole Plant
4.27a
156.41
Flower
0.92b
Sweep net
O.OOb
Termi na l
0.23
216.0
Homoptera: Cicadellidae
Empoasca Labae (Harris)
nymphs
Whole Plant
2.36a
1n.33
+
adults
Sweep net
22. nb
66.70
Terminal
0.07
380.56
70
Table 3.5. (cont'd)
Sampling
Insect
Sampling
date
status
Insect species/group
techniques
X
CV
Predators
Hemiptera: Lygaeidae
Geocoris spp.
nymphs
Whole Plant
O.OCa
+
/
adults
Sweep net
1.8~b
143.93
Termi na l
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
Whole Plant
2.28a
8.79
+
adults
FJower
O.OOb
Sweep net
2.06a
Terminal
0.09
547.72
7/25
Pests
Thysanoptera: Thripidae
Frankliniella fusca
(Hinds)
-immatures
Whole Plant
80.60a
101.12
Flower
119.92b
53.74
adults
Plant
36.12a
101. 90
Flower
89.94b
91.47
Terminal
5.80
48.43
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
l arvae
Whole Plant
Il. 28a
101. 55
Flower
Il. 09b
Sweep net
33.35c
68.75
Termi na l
0.73
123.71
Lepidoptera: Gelechiidae
Stegasta bosqueella
(Chamb.)
l arvae
Whole Plant
0.85a
168.91
Flower
1.23a
Sweep net
1. 72a
199.07
Termi na l
0.03
547.72
Homoptera: Cicadellidae
Empoasca fabae (Harris)
nymphs
Whole Plant
1.97a
175.01
+
adults
Sweep net
70.36b
64.45
Termi na l
0.00
71
Table 3.5. (cont'd)
Sampling
Insect
Sampling
date
status
Insect species/group
techniques
X
CV
Predators
Hemiptera: Lygaeidae
Geocoris spp.
nymphs
Whole Plant
o.17a 223.61
+
/
adults
Sweep net
4.25b
146.33
1"
Termi na1
0.00
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
Whole Plant
1.95a
30.80
+
adults
Flower
2.lla
15.71.
Sweep net
O.OOb
Termi na1
8/02
Pests
Thysanoptera: Thripidae
Frankliniella fusca
(Hinds)
immatures
Whole Plant
72.28a
108.64
Flower
89.65a
86.36
Termi na l
4.53
83.29
adults
Whole Plant
48.50a
103.05
Flower
36.85a
125.63
Termi na1
0.90
117.99
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
1arvae
Whole Plant
10.37a
80.51
Flower
5. lIb
Sweep net
88.64c
52.29
Termi na1
0.73
123.71
Lepidoptera: Gelechiidae
Stegasta bosqueella
(Chamb.)
1arvae
Whole Plant
5.09a
153.18
Flower
0.37b
Sweep net
0.68b
180.97
Termi nal
0.03
547.72
72
Table 3.5. (cont'd)
Sampling
Insect
Sampling
date
status
Insect species/group
technique
X
CV
Homoptera: Cicadellidae
Empoasca fabae (Harris)
nymphs
Whole Plant
5.46a
162.18
,
+
/
adults
Sweep net
141. 27b
48.23
r
Termi na l
0.00
Preda tors
Hemipter: Lygaeidae
Geocoris spp.
nymphs
Whole Plant
0.21a
223.61
+
adults
Sweep net
2.68b
185.06
Termi nai-·
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
Who le Pl ard:
2.51a
19.76
+
adults
Flower
0.55b
18.91
Sweep net
o.18b
Termi na l
0.00
8/08
Pests
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
l arvae
Whole Plant
4.24a
181.87
Sweep net
50.18b
74.56
Termi na l
Lepidoptera: Gelechiidae
Stegasta bosqueella
(Chamb.)
l arvae
Whole Plant
54.24a
94.30
Sweep net
3.47b
173.39
Terminal
Homoptera: Cicadellidae
Empoasca fabae (Harris)
nymphs
Whole Plant
9.70a
108.04
+
adults
Sweep net
114.55b
66.56
Terminal
73
Table 3.5. (cont'd)
Sampling
Insect
Sampling
date
status
Insect species/group
techniques
X-
CV
Predators
Hemiptera: Lygaeidae
Geocoris spp.
nymphs
Whole Plant
O.OOa
,
+
/
adults
Sweep net
5.99b
153. II
r
Terminal
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
Whole Plant <>
4.23a
28.79
+
adults
Sweep net
O.OOb
Termi nal
8/18
Pests
Lepidopter3: Noctuidae
Hel iothis zea (Boddie)
1arvae
Whole Plant
2.68a
142.19
Sweep net
4.21a
142.58
Terminal
Lepidoptera: Gelechiidae
Steqasta bosqueella
(C~amb. )
1arvae
Whole Plant
3.92a
187.50
Sweep net
5.42a
155.22
Terminal
Homoptera: Cicadellidae
Empoasca fabae (Harris)
nymphs
Whole Plant
4.7la
150.56
+
adults
Sweep net
176.84b
54.45
Termi na1
Predators
Hemiptera: Lygaeidae
Geocoris spp.
nymphs
Whole Plant
O.OOa
+
adults
Sweep net
20.32b
64.51
Termi nal
74
Table 3.5. (cont/d)
Sampling
Insect
Sampling
date
status
Insect species/group
techniques
X-
CV
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
Whole Plant
0.6Ia
169.25
+
adults
Sweep net
O.OOa
Termi nal
8/29
Pests
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
l arvae
Whole Plant
6.I5a
140.06
Sweep net
IOO.23b
97.24
Termi na l
Lepidoptera: Gelechiidae
Stegasta bosqueella
(Chamb. )
l arvae
Whole Plant
6.30a
90.57
Sweep net
6.97a
133.98
Terminal
Homoptera: Cicadellidae
Empoasca fabae (Harris)
nymphs
Whole Plant
3.01a
172.47
+
adults
Sweep net
119.24b
49.22
Terminal
Predators
Hemiptera: lygaeidae
Geocoris spp.
nymphs
Whole Plant
0.20a
223.61
+
adults
Sweep net
27.99b
65.84
Terminal
Hemiptera: Anthocoridae
Or;us insidiosus (Say)
nymphs
Whole Plant
O.OOa
162.68
+
adults
Sweep net
O.OOa
Termi na l
75
Tabel 3.5. (cont'd)
Sampling
Insect
Sampling
date
status
Insect species/group
technique
cv
9/07
Pests
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
l arvae
Whole Plant
0.2~a
Sweep net
8.86b
Termi na l
r
Lepidoptera: Gelichiidae
Stegasta bosqueella
(Chamb. )
l arvae
Whole Plant
3.37a
Sweep net
O.OOb
Termi na l
Homoptera: Cicadellidae
Empoasca fabae (Harris)
nymphs
Whole Plant
1. 74a
+
adults
Sweep net
17.79b
Term-j na l
Pedators
Hemiptera: Lygaeidae
Geocoris spp.
nymphs
Whole Plant
0.53a
134. II
+
adults
Sweep net
3.15b
138.22
Termi na l
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
Whole Plant
O.17a
141.14
+
adults
Sweep net
O.OOb
Terminal
1. Mean number of insects/25 plants for the plant, flower, and
sweep net sampling methods, and X no. insects/l0 terminals for the
terminal sampling method.
2. CV
= coefficient of variation.
76
LITERA TURE C!TED
Arthur, B. W., L. L. Hyche, and R. H. Morent.
1959.
Control of the
rednecked peanutworm on peanuts.
J. Econ. Entomol. 52:468-470.
Bissell, T. L.
1941.
A micro leafworm on peanuts.
J. Econ. Entomol.
35:104.
Byerly, K. F., A. P. Gutierrez, R. E. Jones, and R. F. Luck.
1978.
A
"1
comparison of sampling methods for some arthropod populations in
cotton.
Hilgardia 46:257-282.
Cherry, R. H., K. A. '..Jood, and W. G. Ruesink.
1977.
Emergence trap and
sweep riet sampling for adults of the potato leafhopper from
alfalfa.
J. Econ. Entomol. 70:279-282.
Davis, D. L.
1979.
Population dynamics and natural mortality of
several Geocoris spp. in the peanut agroecosystem.
Am. Pean ut
Res. Educ. Assoc. 11:65.
(Abstract).
Davis, D. L.
1981.
Population dynamics of four species of Geocoris
in the peanut agroecosystem.
Ph.D. Dissertation.
Texas A&M Univ.
Delong, D. M.
1932.
Some problems encountered in the estimation of
insect populations by the sweeping method.
Am. Entomol. Soc. Am.
25:13-17.
Dumas, B. A., W. P. Boyer, and W. H. Whitcomb.
1964.
Effect of various
factors on survesy of predaceous insects in soybeans.
J. Ka.
Kentomol. Soc. 37:192-201.
Ellington, J., K. Kiser, G. Ferguson, and M. Cardenas.
1984.
A
comparison of sweepnet, absolute, and insectavac sampling methods
in cotton ecosystems.
J. Econ. Entomol. 77:599-605.
77
Fleischer, S. J., i~. J. Gaylor, and J. V. Edelson.
1985.
Estimating
absolute. density from relative sampling of b.:i9..Y.i lineolaris
(Heteroptera: Miridae) and selected predators in early to mid-
season cotton.
Environ. Entomol. 14:709-717.
Gonzalez, A. G., and T. E. Leigh.
1982.
Three methods for sampling
arthropod numbers on California cotton.
Environ. Entomol. 11:565-
572.
"
Harrisson, F. P.
1959.
Corn earworm oviposition and the effect of DDT
on the egg-predator complex in corn silk.
J. Econ. Entomol.
53 : 1088 - 1094 .
Kinzer, R. E., C. S. Cowan, R. C. Ridgway, J. W. [lavis, Jr., J. R.
Coppedge and S. L. Jones.
1977.
Populations of arthropod
predators of Heliothis spp. after applications of aldicarb and
monocrotophos to cotton.
Environ. Entomol. ~:13-16.
Lewis, T.
1973.
Thrips, Their Biology, Ecology, and Economie
Importance.
Acad. Press, New York.
349 p.
Linker, H. M., F. A. Johnson, J. L. Stimac, and S. L. Poe.
1984.
Analysis of sampling procedures for corn earworm and fall armyworm
(Lepidoptera: Noctuidae) in peanuts.
Environ. Entomol. 13:75-78.
Metcalf, C. L., W. P. Flint, and R. L. Metcalf.
1962.
The potato
leafhopper.
Pp. 441-457.
In Destructive and Useful Insects.
McGraw-Hill Book Co., New York.
1087 p.
Morgan, L. W.
1979.
Economie thresholds of Heliothis species in
peanuts.
Pp. 71-74.
In Economie Thresholds and Sampling of
Heliothis Species on Cotton, Corn, Soybeans and Other Host Plants.
Southern Coap. Series, No. 231.
78
Morris, R. F.
1955.
The development of sampling techniques for
forest insect defoliators, with particular reference to the spruce
budworm.
Cano J. Zool. 33:225-293.
Morris, R. F.
1960.
Sampling insect populations.
Ann. Rev. Entomol.
5:243-264.
,
Roach, S. H., J. W. Smith, S. B. Vinson, H. M. Graham, and J. A.
/
r
Harding.
1979.
Sampling predators and parasites of Heliothis
spp. on crop and native plants.
Pp. 132-145.
In Economie
Thresholds and Sampling Heliothis Species on Cotton, Corn,
Soybeans and Dther Host Plants.
Southern Coop. Series, No. 231.
Semtner, P. J.
1979. 'Insect predators and pests of tobacco following
applications of systemic insecticides.
Environ. Entomol. 8:1095-
1098.
Shepard, M., G. R. Carner, and S. G. Turnipseed.
1974.
A comparison
of three sampli'l~ methods for arthropods in soybeans.
Environ.
Entomol. 3:227-232.
Simonet, D. E., R. L. Pienkowski, D. G. Martinez, and R. D. Blakeslee.
1978.
Laboratory and field evaluation of sampling techniques for
the nymphal stages of the potato leafhopper on alfalfa.
J. Econ.
Entomol. 70:841-842.
Smith, J. W., E. A. Stadelbacher, and C. W. Gantt.
1976.
A comparison
of techniques for sampling beneficial arthropod populations
associated with cotton.
Environ. Entomol. 5:435-444.
Southwood, T. R. E.
1978.
Ecological methods with particular
reference to the study of insect populations.
Chapman and Hall,
London.
2nd ed.
524 p.
79
Tappan, W. B.
1986.
Relationship of sampling time to tobacco thrips
(Thysanoptera: Thripidae) numbers in peanut foliage buds and
flowers.
J. Econ. Entomol. 79:1359-1362.
Wall, R. G., and R. C. Berberet.
1979.
Reduction in leaf area of
Spanish peanuts by the rednecked peanutworm.
J. Econ. Entomol.
72:671-673.
Waller, R. A., and D. B. Duncan.
1969.
A Bayes rule for the symetrie
multiple comparison problem.
J. Amer. Stat. Assoc. 64:1684-1699.
Ualton, R. R., and R. Matlock.
1959.
A progress report of studies of
the rednecked peanutworm in Oklahoma.
OK. Ag. Exp. Sta. Proc.
Series.
P. 320.
Wi~son, L. T., and A. P. Gutierez.
1980.
Within plant distribution of
predators on cotton: Comments on sampling and predator
efficiencies.
Hilgardia 48:3-11.
IV.
SEASONAL ABUNDANCE OF SELECTED PEANUT PEST AND BENEFICIAL
1
ARTHROPODS AS INFLUENCED BY PLANT PHENOLOGy
,
/
r
lIdrissa O. Amirou and Robert E. Lynch.
1989.
To be submitted
to J. Environ. Entomol.
so
ABSTRACT
Seasonal abundance of several species of insect pests and
beneficial arthropods in peanut, Arachis hypogaea L., was investigated
by wee'ly sampling of plots during the growing seasons of 1986, 1987 and
/'
1988, at Tif ton, GA.
In addition, the relationship between the
occurrence and abundance of these arthropods and phenological growth
stages of peanut was examined.
Populations of Frankliniella fusca
, .
(Hinds) in peanut terminals always reached.pei1k densities in the early
vegetative stages of plant growth and declined sharply at the onset of
flowering.
More adult thrips were observed in flowers than terminals.
Densities of lepidopterous larvae, Heliothis zea (Boddie), Elasmopalpus
lignosellus (Zeller), and Stegasta bosgueella (Chambers), were generally
highest from mid-July to late August and, except for ~. bosgueella,
coincided with the growth stages of pean ut most susceptible to leaf
damage, stages R2 - R6.
Population levels of predatory arthropods were extremely low during
the first few weeks of each season, gradually increased as the season
proceeded, and peaked from mid-August to early September.
Spiders and
Geocoris spp. were more abundant than other predators.
Parasitic wasps,
Microplitis croceipes (Cresson), Pristomerus spinator (F.),
Cardiochiles nigriceps Viereck, Netelia heroica Townes, and Meteorus
spp., as a group, were most abundant during the last two weeks of
August.
81
One of the most important principles of integrated pest management
is that no control measure should be applied against an agricultural
insect pest unless the pest is known to be present at populations
sUfficientl~ large to cause economic damage (Stern et al. 1959). This
principle has prompted extensive studies directed toward the
identification of seasonal fluctuations of populations of insect pest
species attacking major crops, including peanut.
Most of the
investigations have been conducted on crops oth~r than peanut, notably
corn (Dicke 1939, Lincoln 1972), cotton (Gaines 1932, 1933), soybean
(Johnson et al. 1975) and grain sorghum (Graham et al. 1972).
Most literature on the abundance of pests in peanut is directed
primarily toward the biology or control of a single insect species, i.e.
the tobacco thrips, Franklinella fusca (Hinds),- the lesser cornstalk
borer, Elasmopalpus lignosellus (Zeller), the potato leafhopper,
Empoasca fabae (Harris), etc.
Leuck (1967) reported that populations of
lesser cornstalk borer usually build up late in the growing season in
GA, and, consequently, do little damage to peanut seedlings.
Morgan
(1975) reported that the greatest damage to peanut by H. zea is
caused by third generation larval populations which appear in peanut in
early August.
Lynch and Garner (1980) reported increased damage in
August by Heliothis zea (Boddie) on late planted peanut.
However,
because insect pests frequently occur in mixed populations in peanut
fields, an evaluation of the seasonal abundance of pests as complexes
instead of individual species, is needed to further the understanding of
82
83
overall dynamics of pest populations in the pean ut agroecosystem.
Ideally, predator and parasite complexes also should be included in
investigations of seasonal densities/abundance of insect pests.
Comprehensive studies on the entire arthropod associations in peanut are
lacking in the literature.
Similarly, since peanut growth and develop~nt associated with the
1
growing season environment predispose the plant ,to damage only during
certain "damage windows," it is imperative that studies on seasonal
abundance of insects and their damage to plants, and resulting yield
loss be associated to plant phenology (Smith 1980, Smith and Barfield
1982).
However, little research on pean ut has addressed the
aforementioned insect/plant relationships.
Most studies, which have
investigated the relationship between damaging populations of insect
pests and plant age at time of damage, degree of damage, or yield, have
been carried out in controlled conditions of laboratories or greenhouses
(Nickle 1976, Huffman and Smith 1979).
This study was designed to provide information on seasonal
abundance of several peanut insect pests, their associated predators and
parasites, and the relationship between their occurrence and plant
phenol ogy.
Materials and Methods
Florunner peanut Arachis hypogaea L., was planted on May 19, 1986,
June 4, 1987, and June 2, 1988 at the Bellflower Farm, near the Coastal
Plain Experiment Station, Tif ton, Georgia.
Seed was planted at the rate
of ca. 113 kg/ha in plots of 1.62 hectares.
Peanuts were grown under
dryland conditions and depended exclusively on rainfall for moisture
84
(Table 4-1).
Standard production practices were followed, excluding the
use of insecticides.
Weekly samples of insect pest species and their associated
predators and parasites were taken from June 19 to August 28, 1986, from
June 30 to September 1, 1987, and from June 20 to September 7, 1988.
Sampled units included excised terminals and flowers, sweepnet
collections from standing plants, and whole-plant collections.
The survey field was subdivided into five replications in 1986,
"
and into six replications in 1987 and 1988 to ensure suitable sample
distribution.
Five weekly samples were taken from each replication on
randomly chosen rows and sample sites.
During 1986, each sweep sample
consisted of 10 sweeps with a 38.1-cm diameter sweep net taken as the
investigator walked along the peanut row.
Each sweep net sample was
lncreased to 25 sweeps in 1987 and 1988.
Whole plant samples consisted
of collections of insects made from plants within each 0.5 row meter on a
randomly selected row using a rectangular area sampler, O.5m x O.3m x
0.2m.
Plants to be sampled were quickly pulled, placed in labeled
plastic bags, and carried back to the laboratory for processing.
Whole
plant sample processing began by submerging plant samples in a solution
of 1.0% sodium hypochlorite in 18.9 liter plastic containers, where they
were agitated ca. every 3.5 minutes for ca. 30 minutes.
Plants were
then removed from the solution, held above the container and thoroughly
rinsed using a hose to dislodge individual insects still remaining on
the plants.
The final wash solution was poured through a series of 10-,
20-, and 100-mesh sieves.
The 100-mesh sieves containing insects were
then backwashed in 100 millimeter plastic cups.
Insects were identified
and counted with the aid of a dissecting microscope.
85
Ten unopened terminal buds were collected and placed in 118 ml
capped plastic cups containing approximately 50 ml of 70% ethanol for
each of five samples randomly selected within each replication.
The
terminals were agitated for ca. 1 min. and carried back to the
laboratory where the cup contents were poured into petri dishes and the
/
insects identified and counted with the aid of a dissecting microscope.
r
Ten flowers also were collected from randomly selected rows for each of
five samples/replication and processed in the same manner as .gescribed
for terminals.
Growth stages of peanut &lsc were recorded on each samp1ing date
(Table 4-2).
The method described by Soote (1982) for differentiating
vegetative (V) and reproduct~ve (R) peanut stages was fo110wed to
determine the successive pea~ut growth stages corresponding to sampling
dates.
Sased on this method, peanut plants in stage VI had on1y one
developed node with one tetrafoliate leaf unfolded, V2 had two developed
nodes, V3 had three developed nodes, and so forth.
The determination of
R stages was based on events related to f10wering, pegging, fruit
growth, seed growth, and maturity.
Plants with one open f10wer at any
node were placed in stage RI (beginning b100m).
Plants with one
elongated peg were classified R2 (beginning peg), and plants with one
peg penetrating the soil with turned swollen ovary, one ful1y-expanded
pod, one pod with cavity apparently fi1led by the seeds when fresh, and
plants with one pod showing visible natura1 coloration of tests were
placed in stages R3 (beginning pod), R4 (full pod), R5 (beginning seed),
R6 (full seed), and R7 (beginning maturity), respectively.
All sJlI1ples "-Iere taken at approximately the same time of the day.
Sampling was beyun ~hen plants were in late vegetative stage (V7) and
86
continued until R7, in 1986 and 1988.
In 1987, however, sampling was
begun and discontinued at earlie; plant stages, V3 and R6, respectively.
Results and Discussion
Insect Pests
The tobacco thrips, f. fusca (Hinds), was continuously
/
collected From peanut terminals and flowers throughout the growing
l'
seasons during the 3-year study.
Overall thrips populations were
highest in 1987 and lowest in 1988.
Population fluctuations vary From
year to year due primarily to normal short-term temperature and rainfall
variations (lewis 1973).
Densities as high as 4 - 6 thrips/peanui
terminal were observed.
Tappan and Gorbet (1979) reported that one or
fewer thrips/terminal was capable of inflicting severe in jury to pean~t
during the early stage of plant growth.
Thrips densities observpd in
this study, however, were much lower than the density of 28
thrips/terminal reported by Lynch et al. (1984).
Thrips in peanut terminals were always most numerous during early
growth stages of peanut (Table 4-3).
In the later stages of growth,
thrips populations in the terminals gradually declined, although the
trend varied slightly in 1987 when thrips populations peaked again in R2
and then declined to the lowest level late in the growing season.
Thrips populations in flowers fluctuated widely, but also showed a
general decline in numbers From early bloom, RI, through completion of
flowering, ca. R6.
During flower productions, thrips populations
remained much higher in flowers than in terminals.
Sams and Smith
(1978) also reported that the decline of thrips populations in terminals
coincided with the onset of flowering of peanut.
Smith and Barfield
87
(1982) postulated that the decline of thrips density in terminals at the
onset of flowering may be due to a dilution of the population from a few
terminals early in the season ta the numerous flowers later in the
season.
Tappan (1986a, b), however, reported that seasonal
proliferation of tobacco thrips feeding sites had no dilution effect on
the number of thrips per site, and that a factor, other than dilu~ion,
was responsible for the decline of thrips populations in peanut
r
terminals.
As shown in Table 4-3, immature thrips were more abundant in
terminals than adults, while adults were more numerous th an immatures
in flowers.
These results verify the observations by Tappan (1986b)
that adult thrips are predominant in flowers while immature thrips are
more numerous in terminal buds.
However, they contradict Hammons and
Leuck (1966) who stated that immatures dominate thrips populations in
both terminals and flowers of Florunner peanuts.
Corn earworm, li. zea, lesser cornstalk borer, f. lignosellus, and
red-necked peanutworm, i. bosqueella, were the most common lepidopterous
pest species found in peanut throughout the study.
Their seasonalities
between years, however, were slightly different (Fig. 4-2).
In 1986, populations of corn earworm larvae rapidly increased from
less than 0.5 larva/m of row on June 30 to ca. 2.5 larvae/m of row
on July 14, but declined to approximately 0.5 larvae/m of row the following
week.
A second peak occurred at the beginning of August, when larvae
reached a density of almost 3 larvae/m of row wh en plants were at peak
flowering, i.e., growth stages R2-R5 (Table 4-4).
Pean ut has been
reported to be most sensitive to defol iation during flowering (Nickle
1976, Jones et al. 1982, Smith and Barfield 1982).
Hudson et al.
88
(1985) also observed two generation peaks of corn earworm on peanut.
Morgan (1979) reported that the August generation of corn earworm is
the most destructive to peanut in Georgia.
In 1987, populations of corn earworm larvae slowly increased and
reached a peak density of almost 4 larvae/meter of row about mid-August.
Again two population peaks were observed, with the first peak in early
August instead of in mid-July as in 1986 (Fig. 4-2).
As in 1986,
however, the highest larval populations in 19870ccurred when pean ut
plants were most sensitive to defoliation, i.e., in stages R4-R6.
Only in 1988 did populations of corn earworm larvae reach levels
higher th an 4 larvae/meter of row for a substantial length of time,
i.e., for 2 weeks or longer (7/25 and 8/02) (Fig: 4-2).
This population
density, howeve~, was still lower th an the proposed economic threshold
of 4 larvae or more/0.30 m of row by Morgan (1979) for Georgia.
Thus, in
all three years, population densities of H. zea larvae were well below
the economic threshold for peanut.
These results agree with the results
of French (1973) and Morgan (1979), who found that populations of corn
earworm larvae seldom reached the economic threshold in peanut, except
in mixed populations with other defoliating lepidopterous species.
Fluctuations in populations of H. zea moths generally coincided
with peak larval populations in each year (Fig. 4-2).
Gaines (1932)
found no correlation between moth population and oviposition in cotton
fields, and speculated that the lack of correlation was due to movement
of moths from field to field.
Peak moth populations occurred much later
in 1987 th an either in 1986 or 1988.
Similarly, the highest moth
densities were obtained in 1987.
Population trends of corn earworm
adults in peJnut in 1986 and 1938 were similar and peaked in early
89
August (Fig. 4-2), although a smaller population peaked before August
in 1986.
Seasonal differences in populations of corn earworm are
difficult to explain since many factors interact to influence their
dynamics.
Lincoln (1972) linked variations of the seasonal abundance
of corn earworm primarily to the availability of several species of
favorable hosts.
G~aham et al. (1972) noted the difficulty in
understanding the pOpulation dynamics of H. zea because of extreme
variation in density of wild, early season hosts of the corn earworm
from year to year.
Dicke (1939) listed temperature, soil water, crop
variety, host attractiveness, and source of moths as f~cto;s which
..
contribute to the wide range of corn earworm infestations.
Snow et
al. (1969) and Sparks (1972) stressed the highly migratory nature of
H. zea moths as a main factor affecting the seasonal abundance of corn
earworm in a given area.
The highest moth density during the 3 years occu~red when peanut
plants were flowering.
The preference of corn earworm moths for the
flowering stages of their hosts has been widely reported in literature.
Johnson et al. (1975) found that flowering corn, tobacco, cotton and
soybean was the preferred phenological plant state for oviposition by H.
zea.
They concluded that adult oviposition on flowering plants would
place most eggs on a crop at a time when newly hatched larvae would have
nutritious fruiting plant on which to feed.
Temporal distributions of larvae and adults of the lesser cornstalk
borer (LeS) were quite different in 1986 than in either 1987 or 1988
(Table 4-5).
The estimated density to larvae in 1986 increased rapidly
From a low of less than 2 larvae/m of row in late June-early July to a
peak of al:11ost 6 1Jl'v.le/m of ro',v in the 2nd ',veek of July.
Populations
90
of LCB larvae remained relatively high during most of the peanut growth
stages sampled in 1986, R2-R6 (mid-July to mid-August).
In contrast,
estimated larval populations were extremely low in 1987 and 1988 and
rarely reached densities of 1 larvae/m of row.
The marked difference which occurred among LCB densities in 1986,
1987, and 1988 confirmed previous reports by Luginbilt and Ainslie
(1917), Leuck (1966, 1967), and French (1971) that se~ere lesser
cornstalk borer infestations are often associated with droughty
conditions.
As shown in Table 4-1, rainfall was significantly lower in
1986 than in 1987 or 1988, especially during the months of May and
September.
Hudson et al. (1985) speculated that high populations of [.
lignosellus associated with hot, dry weather, is due to the insect's
ability to complete its life cycle in 30 days during these conditions
instead of the usual 40 days required to complete its life cycle under
conditions with normal rainfall.
Sporadicity of infestations is a well
known characteristic of the LCB that also may have accounted for
variation of its populations densities among years.
Leuck (1967) and French (1971) reported that the greatest damage to
pean ut in Georgia appears to be due to peg and pod feeding by larvae.
Lynch (1984) demonstrated that LCB larvae prefer and survive best when
they feed on peanut pods in the early stages of development, i.e., R2 to
R4 by Boote's descriptive method (1982).
Smith and Holloway (1979) and
Berberet et al. (1979), on the other hand, reported that peg and pod
damage by larvae early in the growing season is less important than LCB
damage to flower axils since peanut plants compensate for pod losses.
Thus, LCB damage to flower axils, pegs and pods may be equally
important.
Under certain combinations of factors, i.e., late plJnting,
91
droughty conditions, etc., build up of larval populations may coincide
with flowering and pegging and podding periods as indicated by the data
obtained in this study in 1986.
Larval densities of the red-necked peanutworm, Stegasta bosqueella,
per 10 plant terminals remained comparatively low throughout 1987 and
1988 (Fig. 4-4).
Although slight increases in populations were observed
during the first and third weeks of July in 1987 and 1988, respectively,
they were followed by a rapid decline.
In 1986, populations slowly
increased from a plateau of approximately 0.32 larvae/10 terminals from
July~21 to August Il, then sharply increased to a maximum denstty of ..3
larvae/10 terminals on August 25 (Table 4-6).
The sudden surge in S.
bosqueella larval population in peanut in 1986 was not explained.
Conflicting reports exist in the literature on the horizontal
di3tribution of the red-necked peanutworm in peanut fields.
In Alabama,
Arthur et al. (1959) noted that 100% infestation of the terminals
frequently occurs in untreated peanut plots.
Bissell (1941) found that
infestation of peanut terminals by S. bosqueela are localized with one
plant having insects in every shoot and adjoining plants having none.
Most published research data, however, appear to agree on the benign
status of S. bosqueela as a peanut pest in the U.S. (Bissell 1941,
Arthur et al. 1959, Walton and Matlock 1959, Berberet and Guilavogui
1980).
Data from the present study also suggest that the red-necked
peanutworm is not an important pest of peanut in South Georgia since the
suggested ecanamic threshold af two or mare larvae/terminal (Wall and
Berberet 1979), is rarely attained.
Adults af the patata leafhopper, Empaasca fabae (Harris), averaged
annually 7-8 adultsjl0 sweeps in 1986 and 12-16 adultsl in 1987 and 1983
92
(Table 4-7).
In 1986, mean leafhopper populations remained essentially
the,same through most plant growth stages that were sampled, except in
R7, when populations sharply jumped to a weekly maximum of 19 adults/l0
sweeps.
The seasonal abundance of f. fabae in 1987 and 1988 was
similar, with populations peaking from early and mid- ta late August
(Table 4-7).
The relatively low number of the potato leafhopper adults
observed in 1986 may have been due to droughty conditions which
prevailed for most of the year.
Delong (1938) found that high relative
humidity is a critical factor influencing survival and abundance of the
potato leafhopper on bean.
Irrigati~n tp.sts conducted in the present
study and reported elsewhere also supported the above hypothesis.
Maximum leafhopper populations in peanut, especially in 1987-1988,
occurred in August, coinciding with plant growth stages R4-RG (GO to 85
days postemergence).
This period is accompanied by a rapid increase.. in
leaf area and the accumulation of photosynthate for translocation to
developing pods (Ketring et al. 1982).
Thus, peanut plants were in
their most attractive and sensitive stages in August.
Metcalf et al.
(1962) also reported that f. fabae is most attracted ta crops when
plants have high sugar levels in vegetative structures.
Predatory Arthropods
Predator populations during this study were generally low.
Therefore, several species of predators were grouped for discussion.
The term spiders is used here generically to comprise various species.
Three species of big-eyed bugs, Geocoris punctipes (Say), ~. uliginosus
(Say), and ~. bullatus (Say) are referred to as Geocoris spp. in the
remainder of the text.
The common name lady beetle is used to designate
bath Hi~J1rnia convergens GUtTin-:'leneville and Coleamegilla maculata
93
(De Geer).
Two nabid species, Reduviolus roseipennis Reuter and
Tropiconabis capsiformis (German), are also combined for discussion.
Thus, the discussion presented here for predators is mostly suggestive
interpolations of species observed.
Spiders.
Spiders were the most frequently collected group of
predators.
In 1986, mean population density of spiders was essentially
constant, except for August 4, when populations fell to less and 1
individual/l0 sweeps (Table 4-8).
Spider populations were generally
lower in 1986 than in 1987 and 1988.
These comparatively low density of
spiders in 198§ ~robably was due to the dry weather which characterized
that year.
Agnew and Smith (1989) reported that population levels of
most species of spiders decline in peanut fields during droughts in
Texas.
Shepard et al. (1974) also found that unseasonably dry weather
reduces populations of spiders in soybean fields.
The numbers of spiders fluctuated widely in 1987 and 1988, reaching
several peaks in both years (Fig. 4-5).
Population peaks in spider
populations occurred in late July, early and mid-August in 1987.
Populations peaked twice in late July and in mid-August in 1988.
Spider populations did not appear to be associated with a definite
phenological stage of peanut.
Although no clear seasonal trend was
detected, higher population densities occurred mainly in late August in
1987 and 1988, and during mid- to late August in 1986.
Agnew and Smith
(1989) reported an increase in density of spiders in peanut as the
season progressed and as the peanut canopy closed.
Smith et al. (1976)
reported that spider populations are the highest in cotton early in the
season.
Shepard et al. (1974), however, observed the highest
populations of spiders on soybean in September.
94
Geocorids.
Geocoris spp. were the next most abundant predators
collected in peanut.
In 1986, populations of adult big-eyed bugs
fluctuated at low populations without a definite seasonal trend.
Geocoris populations also fluctuated in 1987 and 1988, but followed a
less erratic seasonal distribution pattern (Fig. 4-5).
Population peaks
of Geocoris spp. ~ere observed on August 4 and on August 25 in 1987.
A
bimodal population curve also was obtained in 1988, with the first and
second peaks occurring one week earlier and one week later than in 1987,
respectively.
In both years, Geocoris populations reached maximum
densities during the last 2 weeks of August, but dec1jned sharply the
following week to extremely low levels.
The relative fluctuation of
populations in 1987 and 1988 may have been caused by_ the lumping of
sever al species of Geocoris in single entity for counting.
Davis (1981)
reported that populations of fi. pallens and fi. punctipes reached a
maximum density in Texas in mid-July, and mid-Augu~t, respectively.
In relation to peùnut phenology a greater number of big-eyed bug
adults was collected from plants in growth stages R3 to R6 th an from
other stages in 1987 and 1988 (Table 4-8).
Several factors may have
contributed to the abundance of Geocoris spp. on peanut during these
growth stages.
First, Geocoris population build-up may just have
coincided with plant canopy closing (R4-R5) when more space was
available for colonization by various arthropod complexes, including
big-eyed bugs.
Secondly, because Geocoris spp. are also known to feed
on plants (Roach et al. 1979, Crocker and Whitcomb 1980, Davis 1981), it
is likely that they will occur in greater numbers when more succulent
leaves and inflorescences are produced.
Thus, in the absence of
adeqlJate prey big-i?yed bugs may be sllbstantially ;TIare attracted ta
95
peanut plants when these are fast growing and accumu1ating increased
amounts of photosythates in their 1eaves and/or protein in the f10wer
stamens.
Nabids.
The nabids Tropiconabis capsiformis. and Reduvio1us
roseipennis were the next most abundant predators co11ected from pean ut
fields.
Because on1y few specimens of each species were obtained, the
data for both species were poo1ed and presented here as a mean for nabid
density.
Extreme1y 10w populations of nabids were observed in 1986,
probab1y due to the unseasonab1y dry weather during most of the growing
season.
In 1987 and 1988, po~~lations inereased from few individua1s in
the ear1y season and reached their highest densities during 1ate August
to ear1y September (Fig. 4-5).
Actua11y, in 1988, the nabids were
observed on1y from 1ate August to ear1y September (Table 4-7).
Highest
nabid populations in soybean a1so have been reported for (September) in
South Caro1ina (Shepard et al. 1974).
Other predators.
Low populations of lady beet1es, insidiosus f10wer bug, Orius
insidiosus (Say), and the spined soldier bug, Podisus macu1iventris
(Say), a1so oecurred during each of the three years.
No apparent
seasona1 trend or definite association with specifie pean ut pheno1gy was
observed for lady beet1es or Q. insidiosus.
Populations of E.
macu1iventris, however, were observed most1y in August and, to a 1esser
extent, in ear1y September (Fig. 4-5).
Because predators usua11y oeeur in peanut fields in mixed
populations of various species, we investigated their seasona1ity and
association with different peanut phenologies as a single group.
Table
4-9 shO\\>Js the comb i ned week1 y mean number 0f sp i d2rs, fl QI'ler bug, big-
96
eyed bugs, damsel bugs, lady beetles and staphylinid beetles that was
collected by a sweep net in 1987 and 1988.
In both years, predator
densities fluctuated throughout the growing season, being low through
July, notably increasing during August, and declining again in early
September.
Similarly, the highest number of predators in both 1987 and
1988 was observed during the last two weeks of August (Fig. 4-6).
Overall, predator populations correlated well with specifie peanut
growth stages.
In both 1987 and 1988, appreciably higher population
levels occurred between plant growth stage R3 to R6 (beginning pod to
f~ll ~eed).
Marston et al. (1979) also observed a significantly higher
density of several predators during the early pod-fill stage of soybean
plants.
parasitic Hymenoptera.
The hymenopterous parasite Microplitis croceipes (Cresson),
~~is~omerus spinator (Fabricius), Netelia heroica Townes, Cardiochiles
nigriceps Viereck, and Meteorus sp. were collectively counted as
parasitic wasps and are referred to here as a single entity.
Such
grouping was dictated by two reasons:
(1) individuals of each species
occurred at an extremely low density and (2) many lepidopterous peanut
feeders have common parasites.
Johnson and Smith (1981) reported that
the parasite of the lesser cornstalk borer, f. spinator, also
parasitizes other lepidopteran species, including Feltia subterranea, tl.
zea, Spodoptera exigua (Hubner) and ~. fruqjperda (J. E. Smith).
Wall
and Berberet (1975) discovered that the lesser cornstalk borer and the
red-necked peanutworm, ~. bosqueela, are hosts of M. croceipes.
Lewis
and 8razzel (1968) and Lewis and Vinson (1968) found that, although H.
~eJ is flot a suitJble hast for the develapment of ç. nigriceps, the
97
parasitoid does oviposit in corn earworm larvae, thus lowering its
bjotic potential.
Adult populations of parasitic wasps were low
in each of the three years, especially in 1986, when specimens were
collected only on one sampling date.
Therefore, data on population
densities obtained are presented for only 1987 and 1988 (Table 4-10).
~In 1987, parasite populations fluctuated slightly, and few specimens
!
rwere collected dur'ing the first four weeks of sampl ing .. Parasite
density then increased until mid-August before sharply declining the
following week.
The density of parasitic wasps was consistently
higher in 1988 than in 1987.
The seasonal population trend for adult
parasites for 1988 was similar to tne trend for 1987, with the highest
population peak in August, but one week later than in 1987.
In both
years, an appreciably higher number of parasites was seen during the
last two weeks of August (Fig. 4-i].
Thus, the seasonality of
parasitic wasps in peanut appeared to be similar to the seasonality of
predators.
Similarly, the maximum number of parasites was observed
during R5 and R6 growth stages of peanut.
In summary, the density of adult parasitic wasps was low,
especially during the first 4 to 5 weeks of sampling.
However,
populations gradually increased from low early season density to ca. 13
adultsjsweepnet sample during the last two weeks of August in 1988.
According to Roach et al. (1979), low captures of parasitic wasps should
be expected with sweep nets because adults are relatively strong fliers
and often escape.
In addition, Roach et al. (1979) also reported that
only a few females of parasitic species are generally present in a given
field at any one time, yet this small number may have a significant
impact on host populations.
Price (1976) reporteJ that parasitoids
98
usually experience a high mortality during the early part of the growing
season because they are then exposed to large areas of ground without
food or water, and are subjected to heavy predation while traveling
from plant to plant searching for hosts.
Therefore, Price (1976)
hypothesized that parasitoid populations should remain low until
habitat space (plant canopy) increas~s rapidly and affords a more
/
mesic searing medium for these high1Y mobile arthropods.
Conclusions
The seasonal abundance of the tobacco thrips, f. fusca (Hinds), was
similar in 1986, 1987, and 1988.
Thrips populations in peanut terminal~
were highest during early season, and declined more or less gradually as
the season progressed.
Once flowering began, more thrips were collected
from flowers th an from terminals.
Similarly, adults accounted for a
greater portion of the thrips population in flowers th an in terminals.
The highest thrips density in terminals coincided with growth
stages V7-R1, when vegetative growth was slow and plants were most
susceptible to terminal damage.
Larval populations of the lepidopterous pests, H. zea, [.
lignosellus, and S. bosqueela were low throughout the 3-year study,
although their seasonalities varied among years.
In 1986, the greatest
density of corn earworm larvae occurred form mid-July to mid-August,
coinciding with growth stages R2-RS.
Corn earworm populations were
extremely low during the first few weeks of 1987, but increased sharply
and remained relatively high during most of August, coinciding with R4-
R6 growth stages.
Corn earworm populations were particularly high in
1988, especially From late July to late August.
Although H. zea
99
populations did not reach the proposed economic threshold of 4 larvae or
more/O.30 m of row in any of the three years, corn earworm populations
appear potentially capable of attaining or surpassing this level from mid-
July to mid-August.
Therefore, close monitoring of larval densities of
H. zea on peanut after mid-summer is advisable.
Population densities of ~. bosgueella were extremely low durin1
each of the three years, and the relative population increases thatl'
occurred from late July to early August coincided with growth stages of
peanut when few new terminal buds were added by plants.
Thus, â.
bosgueella is not likely to cause important damage to South Georgia
peanut during most growing seasons.
f. lignosell.us occurred in greater numbers in 1986 than either 1987
or 1988, probably because of droughty conditions which prevailed for
most of the growing season in 1986.
The greatest population build-up of
f. lignosellus occurred from mid-July to mid-August, coinciding with
peanut growth stages R2 to R6 (beginning peg to full seed).
Since the
R2 to R6 growth stages included the period of peak flower production,
damage to flower axils by f. lignosellus may be as important as, or
possibly more important, than its damage to peanut pegs and pods.
Peak predator populations coincided with peak densities of most
insect pest species, i.e., late July to late August.
Although most
predators may be facultatively phytophagous and cannibalistic, their
population levels appeared to be related with
population changes of
potential hosts.
However, more detailed studies are needed on the
seasonal dynamics of predators before we can fully use them as an
augmentative component of the overall control strategy for peanut pests.
100
The princip1es of integrated pest management (IPM) dictate that
app1ied control tactics be used against a pest species on1y when the
pest is known to be present at 1eve1s sufficient1y high to cause
economic damage to crop.
These princip1es a1so advise that control
methods be app1ied in a way to be the 1east destructive to natura1
enemies of insect pests.
These objectives can be on1y attained with a
thorough understanding of seasona1ities of pests and beneficia1
arthropods.
101
/
l'
Figure 4-1.
Seasonal abundance of the tobacco thrips,
Frankliniella fusca (Hinds), on peanut at Tifton, GA, 1986-1988.
Q)
YEAR=BB
a.
E 60
o
V)
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~ Ad u!...!lt'-"s!.-------!..-F--.!.I!....r:::!!.s
---.J
103
_ Figure 4-2.
Seasonal abundance of corn earworm, Heliothis zea
(Boddie), moths and larvae in pean ut at Tifton, GA, 1986-1988.
104
·
o
Z
c
()
<l>
2 0 h
...............~~~--::.r-.~~,.....,....... ...............~,.r-T"",.....,.....,...,.............--.-----ro..........-r-.........--r--r-r-r--T
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.,..,., 87
f3AO 88
105
"
/
l'
Figure 4-3.
Seasonal abundance of lesser cornstalk borer (LeS),
Elasmopalpus lignosellus (Zeller), moths and larvae in peanut at Tifton,
GA, 1986-1988.
106
,
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03JUL
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**~86
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107
/
"
Figure 4-4.
Seasonal abundance of red-necked peanutworm (RNP),
Stegasta bosqueella (Chambers), larvae in peanut at Tifton, GA, 1986-
1988.
109
/
Figure 4-5.
Seasonal abundance of adult nabids, lady beetles,
Geocoris spp., and spiders collected from peanut at Tifton, GA, 1986-
1988.
, . . . - ; -
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Figure 4-6.
Seasonal abundance for combined predator species
collected from peanut at Tifton, GA, 1987-1988.
Mean No. Predators/Sample
<..NO
a
c-,....L----'-----'-----'----'----'----'------~~~..-.....-......----'--
..............................---'---...........L..
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113
./
Figure 4-7.
Seasonal abundance of adult parasittt wasps,
Microplitis croceipes (Cresson) Pristomerus spinator (f.), Cardiochiles
nigriceps
Viereck, Netelia heroica Townes, and Meteorus sp. collected
from pean ut at Tifton, GA, in 1987-1988.
114
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/' W
-------------------
(i)
( / )
1
1
8::::---
1
1
--
o
----
OC)
,
----
,
--
,
--
OC)
,
------
<t>
(9
,,,
:J
,
«
C"-J
~
-.--J
t =>--,t0
[Q'.
C"-J
\\
'
tO
\\'
OC)
-.--J
:=J
--,
t
t0
0
8ldwoS/sdsOM 'oN uoa~
115
Table 4-1.
Average ·monthly rainfall in Tifton, GA, 1986-1988.
Average rainfall (cm)l/
. Mor·th
1986
1987
1988
May
0.97
Il.94
5.84
June
12.37
11.15
6.45
. July
7.77
3.89
9.68
August
12.45
12.24
10.39
September
2.49
13.94
19.76
Total rainfall
38.05 cm
53.16 cm
52.12 cm
1/ As recorded at the Coast al Plain Experiment Station, Tifton, GA.
Table 4-2.
Sampling dates and corresponding peanut growth stages, 198~-1~e.
1986
1987
1988
Plant
Plant
Plant
Sampling
Days after
growth
Sampling
Days after
growth
Sampling
Days after
growth
date
planting
stage l/
date
planting
stage
date
planting
stage
June 19
30
V7
June 24
20
V3
June 20
18
V7
June 30
41
RI
June 30
26
V7
June 27
25
V9
July 7
48
RI
July 7
33
RI
July 5
32
RI
July 14
55
R2
July 1~
40
RI
July 12
39
RI
July 21
62
R3
July 21
47
R2
July 18
45
R2
July 28
69
R4
July 28
54
R3
July 25
52
R3
August 4
76
R5
August 4
61
R4
August 2
59
R4
August Il
83
R6
August Il
68
R4
August 8
66
R5
August 25
90
R7
August 18
75
R5
August 18
76
R6
August 25
82
R6
August 29
87
R6
September l
89
R6
September 9
90
R7
1/
Peanut growth stages based on description proposed by Boote (1982).
......
......
Q)
117
Table 4-3.
Seasonal abundance of immature and adult thrips, [rankllnlella
Iust! (Ilinds), on peanut at Tlfton, GA, cO'l1ecled from dlfferent growlh stages
of plants, 1986-1988.
/
Plant
Xno. thrlps/l0 terminaIs
Xno. thrips/IO flowers
growth
Year
Date
stage l/
Immatures
Adults
Total
Immatures
Adults
Total
1986
6/30
RI
11.24
1. 48
12.72
4.96
7.52
12.48
1987
6/30
V7
47.77
1.80
49.57
1988
6/27
V9
59.57
2.03
61.60
1986
7/07
RI
25.20
1. 24
26.44
9.48
11.96
21.44
1987
7/07
RI
57.20
3.20
60.40
1988
7/05
RI
39.53
2.50
42.03
1986
7/14
R2
9.08
2.32
Il.40
Il.24
12.16
23.40
1987
7/14
RI
17.86
3.16
21.02
8.23
29.13
37.36
1988
7/12
RI
15.50
2.33
17.83
7.53
6.20
13.73
1986
7/21
R3
12.60
1.60
14.20
13.96
7.68
21.64
1987
7/21
R2
40.03
4.47
44 .50
20.40
26.43
46.83
1988
7/18
R2
7.53
.83
8.36
6.67
8.43
15.10
1986
7/28
R4
12.53
1. 56
14.09
9.08
12.80
21.88
1987
7/28
R3
25.0]
2.43
27.46
29.2]
7.10
]6.]3
1988
7/25
ln
5.08
1.10
6.90
4.90
4.2]
9.13
118
Table 4-3 (Cont.)
Plant
;
Xno. thrlps/IO termlnals
Xno. thrlps/IO flowers
1
!
growth
r
Year
Date
stage l/
Immatures
AduHs
Total
Immatures
MuHs
Total
1986
8/04
R5
7.20
1. 96
9.16
7.08
16.44
23.52
1987
8/04
R4
6.40
1.23
7.63
6.07
Il. 43
17.50
1988
8/02
R4
4.53
.90
5.43
4.20 -.
2.07
6.27
1986
8/11
R6
5.40
2.00
7.40
1. 52
1.80
3.32
1987
8/ll
R4
3.20
2.10
5.30
1988
8/08
R5
1/
Peanut growth stages based on description proposed by Boote (1982).
119
Table 4-4.
Seasonal abundance of larvae and adults of the corn
earworm, Heliothis zea (Boddie), in peanut at Tifton, GA, collected
from different growth stages of plants, 1986-1988.
Xno. of ~ zea/sample
Plant
growth
Larvae 2/
Adults 3/
Year
Date
stage 1/
X
Range
X
Range
1986
6/30
RI
0.12
o - 1
0.00
0-0
1987
6/30
V7
0.03
o - 1
0.00
0-0
1988
6/27
V9
0.23
0
3
0.00
0
0
1986
7/07
RI
0.64
o - 1
0.00
o - 0
1987
7/07
RI
0.03
o - 1
0.00
0 - 0
1988
7/05
RI
0.03
o - 1
0.00
0 - 0
1986
7/14
R2
1. 24
0-3
0.16
o - 2
1987
7/14
RI
0.20
0 - 3
0.13
o - 2
1988
7/12
RI
0.47
0 - 4
0.03
o - 1
1986
7/21
R3
0.28
0 - 6
0.00
o - 0
1987
7/21
R2
0.10
o - 1
0.20
0 - 2
1988
7/18
R2
1. 93
0 - 7
0.07
o - 1
1986
7/28
R4
1. 24
0 - 2
0.32
o - 1
1987
7/28
R3
0.17
o - 2
0.27
o - 2
1988
7/25
R3
2.33
o - 14
0.41
0 - 3
120
Table 4-4 (Cont.)
X no. of ~ zea/sample
Pl ant
growth
Larvae 2/
Adults 3/
Year
Date
stage 1/
X
Range
X
Range
1
i
1986
8/04
1"
R5
1.40
a - la
0.64
a - 2
1987
8/04
R4
0.67
a - 2
0.10
a - 2
1988
8/02
R4
2.03
a - 5
0.50
a - 2
.-
1986
8/11
R6
0.84
0-4
.0. ~:6
a - 4
1987
8/11
R4
1.83
a - 6
0.40
a - 2
1988
8/08
R5
0.50
a - 6
0.59
a - 3
1986
1987
8/18
R5
0.47
a - 3
l.40
a - 4
1988
8/18
R6
0.53
a - 3
0.43
a - 2
1986
8/25
R7
0.20
a - 2
0.28
a - 2
1987
8/25
R6
1.03
a - 4
1.80
a - 5
1988
8/29
R6
1.10
a - 4
0.40
a - 2
1986
1987
9/1
R7
0.67
a - 2
0.43
a - 2
1988
9/7
R7
0.07
a - 1
0.33
a - 2
1/
Peanut growth stages based on description proposed by Soote (1982).
2/
Nean numbers per 1/2 111 row.
3/
r'lean numbers per la S'ileeps, 1986, and l11ean numbers per 25 sweeps,
1937, 1988.
121
Table 4-5.
Seasonal abundance of larvae and adults of the lesser
cornstalk borer (LeS), Elasmopalpus lignosellus (Zeller), in pean ut
at Tifton, GA, collected from different growth stages of plants, 1986-
1988.
X no. of LCB/sample
Plant
1
growth
Larvae 2/
Adl.n ts 3/
Year
Date
stage 1
X
Range
X
Range
1986
6/30
RI
0.56
o - 3
0.04
0 - 1
1987
6/30
V7
0.60
--0 - 3
0.00
0 - 0
1988
6/27
V9
0.77
0 - 4
0.00
0 - 0
1986
7/07
RI
0.72
0 - 3
0.28
o - 1
1987
7/07
RI
0.03
o - 1
0.00
0 - 0
1988
7/05
RI
0.10
0 - 3
0.00
o - 0
1986
7/14
R2
2.72
o - 10
0.36
o - 2
1987
7/14
RI
0.10
o - 1
0.03
o - 1
1988
7/12
RI
0.20
o - 1
0.23
o - 2
1986
7/21
R3
2.08
0 - 6
0.04
o - 1
1987
7/21
R2
0.03
o - 1
0.23
o - 2
1988
7/18
R2
0.13
o - 1
0.47
o - 2
1986
7/28
R4
1.12
o - 6
1.80
0 - 7
1987
7/28
R3
0.43
0 - 3
0.30
o - 2
1988
7/25
R3
0.30
o - 2
0.24
o - 1
122
Table 4-5 (Cont.)
Xno. of LCB/sampl e
Plant
growth
Larvae 2/
Adults 3/
Year
Date
stage l/
X
Range
X
Range
1986
8/04
R5
1.12
0
6
1.36
0
6
1987
8/04
R4
0.13
0 - 2
0.43
0 - 3
1988
8/02
R4
0.00
a - a
0.40
a - 2
1986
fr/lI
R6
1.48
a
8
0.44
0
4
1987
3/11
R4
0.30
a - 2
0.23
a - 2
1988
3/08
R5
0.00
a - a
0.55
a - 2
1986
1987
8/18
R5
0.07
a - 1
0.17
a - 2
1988
8/18
R6
0.10
a - 1
0.37
a - 2
1986
8/25
R7
0.48
a - 3
0.16
o - 2
1987
8/25
R6
0.07
a - 2
0.33
a - 3
1988
8/29
R6
0.23
a - 2
0.77
o - 2
1986
1987
9/1
R6
0.03
a - 1
0.26
a - 2
1988
9/7
R7
0.17
a - 2
0.00
a - a
1/
Peanut growth stages based on description proposed by Boote (1982).
2/
~'ean numbers per 1/2 m row.
3/
r'lean nurnbers pel' la sweeps, 1986, and mean numbers per 25 sweeps,
1987, 1988.
123
Table 4-6.
Seasonal abundance of red-necked peanutworm, Stegasta
bosque~lla (Chambers), in peanut at Tifton, GA, collected from different
growth stages of plants, 1986-1988.
Plant
X no. of larvae/10 terminals
.
growth
/
stage 1
Year
Date
X
Range
/'
1986
6/30
RI
0.00
o - 0
1987
6/30
V7
0.00
o - 0
1988
6/27
V9
o 00
o - 0
1986
7/07
RI
0.00
a - 0
1987
7/07
RI
0.00
o - 0
1988
7/05
RI
0.06
o - 1
1986
7/14
R2
0.00
o - 0
1987
7/14
RI
0.06
o - 1
1988
7/12
RI
0.03
o - 1
1986
7/21
R3
0.00
o - 0
1987
7/21
R2
0.20
o - 2
1988
7/18
R2
0.00
a - a
1986
7/28
R4
0.32
a - 1
1987
7/28
R3
0.17
a - 1
1988
7/25
R3
0.23
a - 2
124
Table 4-6 (Cont.)
Plant
X no. of larvae/10 terminals
growth
Year
Date
stage 1
,
X
Range
/
l'
1986
8/04
R5
0.32
a - 2
1987
8/04
R4
0.17
a - 2
1988
8/02
R4
0.23
a - 2
1986
8/11
R6
0.32
a - 1
1987
8/11
R4
0.03
a - 1
1988
8/08
R5
0.03
a - 2
1986
8/25
R7
3.04
o - 7
1987
8/25
R6
0.00
a - a
1988
8/29
R6
0.00
o - a
1/
Peanut growth stages based on description proposed by Boote (1982) .
125
Table 4-7.
Seasonal abundance of adult potato leafhoppers,
Empoasca fabae (Harris), in peanut at Tif ton, GA, collected from
different growth stages of plants, 1986-1988.
Plant
X no. of leafhoppers/sample 2/
growth
/
Year
Date
stage 1
X
Range
1"
1986
7/14
R2
8.00
0 - 39
1987
7/14
RI
9.97
0 - 25
1988
7/12
RI
3.83
o - 14
1986
7/21
R3
5.40
o - 12
1987
7/21
R2
18.97
o - 55
1988
7/18
R2
4.17
o - 12
1986
7/28
R4
5.16
o - 13
1987
7/28
R3
12.23
o - 29
1988
7/25
R3
Il. 34
1 - 27
1986
8/04
R5
7.76
0 - 20
1987
8/04
R4
26.60
o - 83
1988
8/02
R4
22.93
0 - 83
1986
8/11
R6
6.28
o - 15
1987
8/11
R4
17.23
0 - 45
1988
8/08
R5
13.03
0 - 27
126
Table 4-7 (Cont.)
Plant
X no. of leafhoppers/sample 2/
growth
Year
Date
stage 1
X
Range
/
1986
r
1987
8/18
R5
15.47
o - 52
1988
8/18
R6
21.30
0 . 48
1986
8/25
RI
19.00
6 - 81
1987
8/25
R6
17.87
7 - 36
1988
8/29
R6
18.13
o - 45
1986
1987
9/01
R6
7.07
o - 15
1988
9/07
R7
2.93
o - 11
1/ Peanut growth stages based on description proposed by Boote (1982).
2/ Each sample consisted of 10 sweeps in 1986, and 25 sweeps in 1987
and 1988.
"Jable 4-8.
Seasonal abundance of predators collected from different growth stages of peanut a~ Tifton. GA.
1986-1988.
Plant
Xno. of adult predators/sample
growth
Na bi ds
Geocoris spp.
Lady beet les
Spi ders
Orious insidiosus 2
Podisus maculiventris 3
Year
Date stage l /
X
Range
X
Range
X
Range
X
Range
X
Range
X
Range
1986
7/14
R2
0.16
0-2
0.56
0-5
0.12
0-2
1.16
0-3
0.00
0-0
0.00
a - a
"----;
............... "
1987
7/14
Rl
0.00
0-0
0.00
0-0
0.07
0-1
1.13
0-6
0.03
0-1
0:00
0-0
1988
7112
RI
0.03
a - 1 0.20 0-1
0.00
a - a 1. 23
0-6
0.17
0-2
0.00
a - a
r
1986
7/21
R3
0.08
a - 1 0.00 a - a
0.16
a . 1 1. 60
0-5
C.OO
0-0
0.08
0-0
1987
7/21
R2
0.57
0-3
0.07
0-1
0.00
0-0
2.70
a - 14 0.06
0-1
0.00
0-0
1988
7118
R2
0.00
0-0
0.30
0-2
0.00
a - a 1.40
0-5
C.OO
0-1
0.03
0-1
1986
7/28
R4
0.12
0-1
0.44
0-2
0.04
a - 1 1. 68
0-5
0.08
0-1
0.00
a - a
1987
7/28
R3
0.97
0-5
0.70
0-3
0.00
0-0
2.53
0-7
0.06
0-1
0.00
0-0
1988
7/25
R3
0.00
a - a 0.79 0-4
0.03
o - 1 1. 95
0-6
0.10
0-1
0.00
0-0
1986
8/04
R5
0.16
0-1
0.04
0-1
0.00
0-0
0.84
0-5
0.00
a - a
0.04
0-1
1987
8/04
R4
0.43
0-1
0.80
0-5
0.00
a - a '2.73
~ ~. 8
0.13
0-1
0.30
0-2
1988
8/02
R4
0.00
a - a 0.43 0-4
0.00
J - a 0.80
':l 7' 4
0.07
0-1
0.13
0-1
t - '
N
'-l
Table 4-8. (Cont.)
Plant
X no. of adult predators/sample
growth
Nabids
Geocor;s spp.
Lady beetles
Spiders
Or;ous insidiosus 2
Pod;sus maculiventris 3
-
Year
Oate stage l /
X
Range
X
Range
X
Range
X
Range
X
Range
X
Range
1986
8111
R6
0.16
0-1
0.44
0-2
0.08
0-1
1.56
0-4
0.08
o - 1
0.04
o - 1
1987
8/11
R4
0.23
0-1
0.73
0-5
0.00
0-0
1. 60
0-6
-
-
0.53
0-3
1988
8/08
R5
0.86
0-4
0.38
0-4
0.00
0-0
2.86
0-6
-
-
0.07
o - 1
1986
1987
8118
R5
1.73
o - 20 1. 90 0-9
0.00
0-0
3.37
0-9
-
-
0.37
0-3
1988
8118
R6
0.90
0-4
2.10
0-7
0.03
0-1
4.67
o - 14
-
-
0.03
0-1
:
1986
8/25
R7
0.20
0-1
0.28
0-2
0.00
0-0
1.40
0-6
.00
0-0
0.20
0-1
198i
8/25
R6
1.30
0-4
1.13
0-5
0.00
0-0
3.13
o - 13
-
-
0.37
o - 2
1988
8/29
R6
0.60
0-2
3.10
0-7
0.03
0-0
4.63
o - 15
-
-
.13
0-2
1986
1987
9/01
R6
0.40
0-3
0.17
0-2
0.00
0-0
1.87
0-8
-
-
0.43
0-2
-.
'--- .-
1988
9/07
R7
0.93
0-4
0.40
o - 3
0.00
0-0
3.47
o - 10
-
-
0.00
0-0
·11
~
1/ Peanut growth stages based on description proposed by Soote (1982).
~
2/ Mean number of nymphs per 10 flowers.
l - '
N
3/ Mean number of adults per 10 sweeps in 1986. and mean number of adults per 25 sweeps ;n 1987 and 1988.
co
129
Table 4-9.
Combined numbers of predators/sweet sample as related
to peanut plant phenology, 1986-1988.
Plant
growth
X no. of all predator species
Year
Date
stage 1/
per sample2/
1986
7/14
R2
1987
7/14
RI
1.50
1988
7/12
RI
2.57
1986
7/21
R3
198]
7/21
R2
3.57
1988
7/18
R2
2.13
1986
7/28
R4
1987
7/28
R3
4.77
1988
7/25
R3
2.93
1986
8/04
R5
1987
8/04
R4
4.17
1988
8/02
R4
1.33
1986
8/ Il
R6
1987
8/11
R4
3.00
1988
8/08
R5
4.48
1986
1987
8/18
R5
8.20
1988
8/18
R6
8.60
130
Table 4-9 (Cont.)
Plant
growth
X no. of all predator species
~ear
Date
stage l/
per sample2/
/
li986
8/25
R7
1987
8/25
R6
6.10
1988
8/29
R6
9.33
1986
1987
9/01
R6
2.57
1988
9/07
R7
4.87
1/ Peanut growth stages based on description proposed by Boote (1982).
2/ Sweep net sample size = 10 sweeps in 1986, and 25 sweeps in 1987,
1988.
Total predators include spiders, a flower bug, big-eyed bugs,
staphylinid beetles, nabids, and lady beetles.
131
Table 4-10.
Seasonal abundance of adult parasitoid wasps,
Microplitis croceipes (Cresson), Pristomerus spinator (Fabricius),
Cardiochiles nigriceps Viereck, Netalia heroica Townes, and
Meteorus sp. from peanut at Tifton, GA, collected on different growth
stages of plants, 1986-1988.
Plant
1
X no. of adult parasitoids per sample2/
growth
1"
Year
Date
stage 1/
X
Range
1986
7/14
R2
0.00
0 - 0
1987
7/14
RI
0.03
o - 1
1988
7/12
RI
0.13
o - 1
1986
7/21
R3
0.00
0 - 0
1987
7/21
R2
0.37
o - 5
1988
7/18
R2
0.60
o - 4
1986
7/28
R4
0.04
o - 1
1987
7/28
R3
0.13
o - 1
1988
7/25
R3
0.14
o - 2
1986
8/04
R5
0.00
o - 0
1987
8/04
R4
0.00
o - 0
1988
8/02
R4
0.13
o - 1
1986
8/ Il
R6
0.00
o - 0
1987
8/11
R4
0.34
0 - 3
1988
8/08
R5
0.34
o - 2
132
Table 4-10 (Cont.)
Plant
X no. of adult parasitoids per sample21
growth
Year
Date
stage 11
X
Range
1986
1987
8/18
R5
0.57
o - 2
1988
8/18
R6
2.97
o - 15
1986
8/25
R7
0.00
0 - 0
1987
8/25
R6
0.20
o - 2
1988
8/29
R6
13 .10
3 - 26
1986
1987
9/01
R6
0.17
a - 1
1988
9/07
R7
0.93
o - 2
11 Peanut growth stages based on description proposed by 800te (1982).
21 Sweep net sample size was la sweeps in 1986, but was increased to
25 sweeps in 1987, 1988.
133
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Ecology of spiders (Araneae)
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/
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134
French, J. C.
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The damage and control of the 1esser cornsta1k
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of soi1 moi sture on its bio10gy.
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French, J. C.
1973.
Insect pest management on peanuts in Georgia.
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/
Gaines, J. C.
1932.
Migration and population studies of the cotton
r
bo 11 wo rm mo t Il .
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1933.
Factors inf1uencing the activities of the cotton
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1972 .
l·h e r ole 0f
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Environ. Entomol. 1: 424-431.
Hammons, R. O. and D. B. Leuck.
1966.
Natural cross-pollination of the
peanut, Arachis hypogaea L., in the presence of bees and thrips.
Agron. J. 58: 396.
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1985.
Peanut pest management.
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57 p.
Huffman, F. R. and J. W. Smith, Jr.
1979.
Bol1worm:
PeanlJt foliage
consumption and larval development.
Environ. Entomol. 8: 465-467.
Johnson, M. W., R. F. Stinner and R. L. Rabb.
1975.
Ovipositional
response of Hel iùthis Iea (Boddie) to its major hosts in North
Carol ina.
Environ. Entomol. 4: 291-297.
Jones, J. W., C. S. Barfield, K. J. Boote, G. H. Smerage and J. Mangold.
1982.
Photosynthetic recovery of peanuts to defoliation at
various growth stages.
Crop Sei. 22: 741-746.
135
Ketring, O. L., R. H. Brown, G. A. Sullivan and O. B. Johnson.
1982.
Growth physiology.
Pp. 411-457.
ln Pattee and Young, (eds.),
Peanut Science and Technology.
Am. Pean ut Res. Educ. Soc., Inc.,
Yoakum, Texas.
825 p.
Leuck, D. B.
1966.
Biology of the lesser cornstalk borer in south
Georgia.
J. Econ. Entomol. 59: 797-801.
/
Leuck, D. B.
1967.
Lesser cornstalk borer damage to pean ut pl~nts.
J.
Econ. Entomol. 60: 1549-1551.
Lewis, T.
1973.
Thrips, their biology, ecology, and economic
importance.
Acad. Press.
New York.
349 p.
Lewis, W. J. and J. R. Brazzel.
1968.
A three-year study of parasites
of the bollworm and the tobacco budworm in Mississippi.
J. Econ.
Entomol. 61: 673-676.
Lewis, W. J. and S. B. Vinson.
1968.
Egg and larval development of
Cardiochiles nigriceps.
Ann. Entomol. Soc. Amer. 61: 561-565.
Lincoln, C.
1972.
Seasonal abundance.
Pp. 2-7.
ln Distribution,
Abundance, and Control of Heliothis Species in Cotton and
Other Host Plants.
Southern Coop. Series Bull. 169.
Luginbill, P. and G. G. Ainslie.
1917.
The lesser cornstalk borer.
U.S. Dep. Ag. Bull. 539.
27 p.
Lynch, R. E.
1984.
Damage and preference of lesser cornstalk borer
(Lepidoptera: Pyralidae) larvae for pean ut pods in different stages
of maturity.
J. Econ. Entomol. 77: 360-363.
Lynch, R. E. and J. W. Garner.
1980.
Effect of planting date on insect
damage and yield.
Proc. Am. Peanut Res. Educ. Soc. 12: 72.
136
Lynch, R. E., J. W. Garner and L. W. r·1organ.
1984.
Influence of
systemic insecticides on thrips damage and yield of Florunner
peanuts in Georgia.
J. Agric. Entomol. 1: 33-44.
Marston, N. L., G. D. Thomas, C. M. Ignoffo, M. R. Gebhardt, D. L.
Hoestetter and W. A. Dickerson.
1979.
Seasonal cycles of soybean
arthropods in Missouri:
Effect of pesticidal and cultural
practices.
Environ. Entomol. 8: 165-173.
Metcalf, C. L., W. P. Flint and R. L. Metcalf.
1962.
The potato
leafhopper.
Pp. 411-457.
ln Destructive and Useful Insects.
McGraw - Hill Book Co., New York, NY.
Morgan, L. W.
19ï9.· Economie thresholds of Heliothis species in
peanuts.
Pp. 71-74.
ln Economic Thresholds and Sampling of
Heliothis spp.
On Cotton, Corn, Soybeans, and Other Host Plants.
Southern Coap. Series Bull. 231.
Nickle, D. A.
1976.
The peanut agroecosystem in Central Florida:
Economic thresholds for defoliating Noctuids (Lepidoptera:
Noctuidae); Associated parasites; Hyperparasitism of the Apanteles
complex (Hymenoptera: Braconidae).
Ph.D. Dissertation.
Univ.
Florida, Gainesville, FL.
Priee, P. W.
1976.
Colonization of crops by arthropods:
Non-
equilibrium communities in soybean field.
Environ. Entomol. 5:
605-611.
Roach, S. H., J. W. Smith, S. B. Vinson, H. M. Graham, and J. A.
Harding.
1979.
Sampling predators and parasites of Heliothis spp.
on crop and native host plants.
Pp. 132-145.
ln Economie
Thresholds and Sampling of Heliothis spp.
On Cotton, Corn,
SoybeJns and Oth,~r Host Phnts,
Southern Coop. Series Bull. 231.
137
Sams, R. L. and J. W. Smith, Jr.
1978.
Evaluations of six insecticides
applied at planting for thrips control on Texas peanuts.
Texas
Agric. Exp. Sta. Prog. Rpt. 3525.
9 pp.
Shepard, M., G. R.. Carner and S. G. Turnipseed.
1974.
Seasonal
abundance of predaceous arthropods in soybeans.
Environ. Entomol .
.
3: 985-988. /
l'
Smith, J. W., Jr.
1980.
Plant phenology and damage from insect pests.
Proc. Am. Peanut Res. Educ. Soc. 12: 71.
Smith, J. W., Jr. and C. S. Barfield.
1982.
Management of preharvest
insects.
Pp. 250-325.
ln Pattee and Young, (eds.),- Peanut Science
and Technology.
Am. Peanut Res. and Educ. Soc., Inc.
Yoakum,
Texas.
825 p.
Smith, J. W., Jr. and R. L. Holloway.
1979.
Lesser cornstalk borer
larval density and damage to peanuts.
J. Econ. Entomol. 72: 535-
537.
Smith, J. W., Jr., E. A. Stadelbacher and C. W. Gantt.
1976.
A
comparison of techniques for sampling beneficial arthropods
associated with cotton.
Environ. Entomol. 5: 435-444.
Snow, J. W., W. W. Cantelo and M. C. Bowman.
1969.
Distribution of the
corn earworm on St. Croix, U.S. Virgin Islands, and its relation to
suppression programs.
J. Econ. Entomol. 62: 606-611.
Sparks, A.
1972.
Heliothis migration.
Southern Coop. Series Bull.
169.
pp. 15-17.
Stern, V. M., R. F. Smith, R. Van Den Bosch and K. S. Hagen.
1959.
The
integrated control concept.
Hilgardia 22: 81-101.
138
Tappan, W. B.
1986a.
Tobacco thrips (Thysanoptera: Thripidae) number
after peanut foliage bud and flower excision.
J. Econ. Entomol.
79: 1082-1084.
Tappan, W. B.
1986b.
Relationship of sampling time to tobacco thrips
(Thysanoptera: Thripidae) numbers in pean ut foliage buds and
flowers.
J. Econ. Entomol. 79: 1359-1369.
/
Tappan, W. B. and D. W. Gorbet.
1979.
Rel at i onshi p iOf seasona l thri ps
populations to economics of control on Florunner peanuts in
Florida.
J. Econ. Entomol. 72: 772-776.
Wall, R. G. and R. C. Berberet.
1975.
Parasitoids associated with
lepidopterous pests on peanutsj Oklahoma fauna.
Environ. Entomol.
4: 877-888.
Wall, R. G. and R. C. Berberet.
1979.
Reduction in leaf area of
Spanish peanuts by the rednecked peanutworm.
J. Econ. Entomol. 72:
671-673.
Walton, R. R. and R. Matlock.
1959.
A progress of studies of the red-
necked peanutworm in Oklahoma.
Oklahoma Ag. Exp. Sta. Proc.
Series.
p. 320.
V.
EFFECT OF IRRIGATION ON POPULATIONS OF SELECTED PEST AND
BENEFICIAL ARTHROPODS OF PEANUT 1
1Idrissa O. Amirou and Robert E. Lynch.
1989.
Ta be submitted
ta J. Agric. Entomol.
139
ABSTRACT
A study was conducted on Florunner peanut, Arachis hypogaea L., in
1986 to determine the effects of irrigation on populations of pest and
pre~ator arthropods.
Irrigation significantly reduced populations of
th~~ps, Frankliniella fusca (Hinds), red-necked peanutworm, Stegasta
bosqueella (Chambers), and lesser cornstalk borer, Elasmopalpus
lignosellus (Zeller).
The number of larvae and adults of Heliothis zea
(Boddie) in irrigated and nonirrigated plots did not differ signifi-
cantly.
Although irrigation had little effect on population estimates
for several insect predators, including big-eyed bugs, insidiosus flower
bugs, lady beetles, and nabids, the number of spiders was significantly
higher in irrigated peanut.
Thus, in addition to its beneficial
effect on pean ut yield, irrigation may ap9reciably reduce populations of
certain insect pests and potentially play an important role in the
management of arthropods in the peanut field.
110
The effects of soil water deficiency and low relative humidity on
peanut growth, reproduction, and maturation have been extensively
reported in the literature.
Boote and Hammond (1981) found that water
deficit, occurring from ca. 40 to 82 day~ after peanut emergence, slowed
vegetative growth by reducing the rate of leaf expansion, node
formation, and stem elongation.
Lee et al. (1972) reported that low
relative humidity (< 50%) at about the same peanut growth period was
detrimental to flower formation, peg initiation and development.
Martin
and Cox (1977) ohserved the greatest reduction in peanut yield wh en
drought coincided with peak peg production and transition of pegs to
pods.
Boote et al. (1982) postulated that soil water deficit during
pegging and pod development interferes primarily with the development of
pods from pegs.
Anticipated effects of soil water deficiencies, often linked
with
rainfall deficits at critical growth stages of peanut, have prompted
many farmers in the southeastern states to adopt irrigation as part of
their routine cultural practices.
Henning (1978) reported that ca. 45%
of the allotted pean ut acreage was under irrigation in Georgia in 1972.
Boo te et al. (1982) speculated that many southeastern farmers would
adopt irrigation because of the increasing value of the peanut crop as
well as to stabilize and/or insure peanut production during rainfall-
deficient periods even though total seasonal rainfall may be adequate
for production.
141
142
Widespread use of irrigation is shown to affect the popula-
tion dynamics of several species of insect pests in cotton (Gaines 1933,
Fletcher 1941, Young and Price 1968, Slossner 1980) and corn (All et al.
1979).
In contrast, little information is available on the effect of
irrigation on populations of pest and beneficial insects encountered in
peanut agroecosystems.
Only the study conducted by Tappan and Gorbet
/
l'
(1986) addressed the influence of irrigation on peanut insects.
However, these authors did not include beneficial arthropods in their
investigations.
Therefore, this research was conducted to stucy the .. direct impact
of irrigation on populations of peanut arthropods.
The potential
indirect effect of irrigation on insect populations through its effect
on the host peanut plants was also investigated.
Finally, the effects
of insect pests and/or irrigation on peanut plant weight and yield were
measured.
Materials and Methods
The studies were conducted at the Bellflower Farm, near the Coastal
Plain Experiment Station, Tifton, Georgia in 1986.
Florunner peanuts,
Arachis hypogaea L., were planted on May 19 in a 1.62 hectare field.
Standard production practices were followed thraughaut the growing
season, excluding insecticides.
Irrigation of ca. 2.50 cm was applied
by a sprinkler system on each date shawn in Table 5-1.
Irrameters, with
sensing elements lacated 15 cm deep in the soil profile, were placed in
each plot and readings of sail-water tension were used as a guide ta
determine the need for irrigation.
143
The experiment was designed in a randomized complete b10ck ~ith
five rep1ications.
Treatments were irrigated versus nonirrigated
peanut.
Arthropod populations were estimated week1y From June 19 to
August 25 using whole plant, terminal, and sweep net samp1ing methods.
The detailed description of these methods are found in Chapter III.
,
Data were also recorded on:
(1) number of plants/O.SO m of row;
/
(2) number of pegs and/or pods/plant;
(3) fresh weight of leaves, pods,
ï
and top parts (stems+1eaves)/p1ant;
and (4) dry weight of 1eaves,
pods, and top parts (stems+leaves)/ plant, for most sampling dates.
At maturity, pods From an area of two rows x 6.1 m/rep1ication were dug
with an inverter, threshed,-an~ dried.
Yields were analyzed by a one-way analysis of variance and
significant1y different means were separated by Wal1er-Duncan's multiple
range test Waller and Duncan (1969).
Proc-univariate analyses were
conducted on week1y arthrùpod and plant data,i.e. 1eaf weight, peg and
pod number, and weight to determine the frequency distributions.
While
plant data generated near normal curves, populations for most
arthropod species approximated clumped or over-dispersed distributions.
Therefore, to stabilize the variance all arthropod data were transformed
to log (x+l).
Subsequent1y transformed data then were ana1yzed by a
one-way ANOVA, and significant1y different week1y means were separated
by Wa11er-Duncan's multiple range test.
Resu1ts and Discussion
Insect Pest Species
The number of immatures and adu1ts of tobacco thrips, E.
fusca, was consistent1y higher on nonirrigated th an on irrigated peanut
throughout the grù,,~ing sCJSon (Table 5-2).
Ho',.;e'/t~r, on most sampling
144
dates differences in the number of adult thrips were not significant,
probably as a result of adu;t migration among treatment plots.
Significant differences in number of immature thrips between
treatments were not noted ~ntil July 7.
Except on two sampling dates,
the number of immatures was significantly higher in nonirrigated than
in irrigated plots From J~ly 7 to August Il.
Lewis (1973) reported
that rainfall or irrigatibn can significantly reduce populations of
thrips (1) by direct drowning or washing them off the leaves or (2) by
its effects on the growth and development of the host plant.
On
peanut, thrips feed and develop primarily within terminals.
Therefore, it is unlikely that irrigation would have a major dir~ct
impact on populations of thrips in peanut.
However, the more ra~id
growth of irrigated peanut plants between July 7 and August Il may
have produced the significant differences between the number of
immature thrips populations that was found in the two treatl~nts.
McCloud (1973) showed that, under adequate moi sture, the growth rate
of peanut plants increased From slow vegetative growth during the
first 40 days after emergence to a more rapid, exponential growth rate
which continued until 80-90 days after planting when maximum growth
was reached.
Lynch et al. (1984) suggested that thrips populations
decline during the exponential growth phase of peanut plants as a
result of their repeated migration; terminals and flowers remain
suitable for feeding for a shorter period of time during the rapid
growth phase; and thrips, especially soft-boddied immatures, are
exposed to predation, parasitism and environmental stress more often
as they lOigrate From one terminal to the other. In the present study,
noni(rigat~d peanut plants \\~ere gro\\~ing at a slc',ler rate (Table 5-3)
145
early in the growing season than were plants in irrigated plots.
However, toward the end of the sampling period, irrigated peanuts had
almost reached their maximum vegetative growth and were developing
fewer terminals than were plants in nonirrigated plots.
Thus, the
major differences in the number of thrips from irrigated versus
nonirrigated peanut probably reflect differences in the suitability ff
the hast for development of immature thrips.
Population estimates for
red-necked peanutworm, ~. bosqueella, corn earworm, H. zea, and lesser
cornstalk borer, 1. lignosellus, larvae as determined by the whole
plant method are presented in Table 5-3.
The whole plant sampling
method estimated larger populations of red-necked peanutworm in
nonirrigated plots than in irrigated plots throughout most of the
sampling period (5-3).
However, significant differences between
irrigation treatments were recorded only in August, which corresponded
roughly with the period of decreased vegetative growth and increased
pod development for the irrigated pean ut (McCloud 1973).
Thus as
previously reported for thrips, these differnces between ~' bosqueella
populations in irrigated and nonirrigated plots were probably due to
fewer terminals being developed by irrigated th an by nonirrigated
pean ut plants.
Significant differences were observed in the number of H. zea only
on two out of the nine sampling dates (Table 5-3).
Even on these dates,
H. zea larval populations were relatively low and did not approximate
the 13.1 larvaejmeter of row recommended as the threshold for defoli-
ating insects on peanut by the Cooperative Extension Service, University
of Georgia.
Thus, irrigation had little influence on populations of!i.
~ea llrv,)e.
fhese results disagree '.vith Tappln )Ild Gorbet (1986) '.vho
146
found thatirrigation reduced infestations by tl. zea and other
lepidopterous foliage feeders on peanuts in Florida.
Estimates for populations of ~ lignosellus were not
significantly different between the two treatments until July 14 when
nonirrigated peanut had a significantly higher number of larvae than
irrigated peanut.
These differences in population of I. lignosellus
larvae remained significant thereafter until the last sampling on August
25 (Table 5-3).
During this period, larval populations in nonirrigated
plots were almost three times higher than populations in irrigated
peanut.
Thus, i~rigùtion applied on July 19 successfully reduced
infestations of lesser cornstalk borer larvae.
These results support
those of All et al. (1979) and Tappan and Gorbet (1986) who also found
that timely applications of irrigation during periods of drought
significantly reduced populations of I. lignosellus on corn
and peanut, respect~vely.
Except for a single sampling date, August 4, estimates for
tl. zea adult populations were not significantly different between
treatments (Table 5-4).
Irrigation also had little effect on popula-
tions of the adult lesser cornstalk borer.
The number of moths was
significantly lower in irrigated than in nonirrigated plots only on two
sampling dates (Table 5-4).
The mobility of adult tl. zea and I.
lignosellus from plots ta plots probably accounted for the lack of
response to treatment effects on most sampling dates.
The patato leafhopper, I. fabae, populations were
significantly higher in irrigated than nonirrigated plots beginning July
14 for j~natures and July 21 for adults and continuing for the rest of
the sai1lplin<] period (fable 5-5). fhese results agree \\~ith those reported
147
by Tappan and Gorbet (1986) \\'Iho a1so found that I. fabae populations
were significant1y higher on irrigated than on nonirrigated peanut.
Plant succulence has been reported to be one of the major factors
responsib1e for the attraction of the potato 1eafhopper to seed1ing
plants growing with adequate soi1 water (De10ng 1938, Metca1f 1962).
Fletcher (1941) ~fined succulence as the weight difference between
fresh and dry p1<fnt vegetative parts.
Because it is obvious from data
presented in Tables 5-8 and 5-9 that irrigated plants were more
succulent than nonirrigated plants, the observed diff~rences in 1eaf-
hopper populations may have ref1ected differences in.physio10gica1
states between irrigated and nonirrigated peanut p1ants~
Arthropod Predators
Population estimates of predators were genera11y low for most
species or groups (Table 5-6).
The number of Geocoris $PP. Orius
insidiosus (Say), Hippodamia converqens Guerin-Menévi11e, and
Co1eomegi11a macu1ata Lengi.
Timber1ake differed 1itt1e between
treatments.
In contrast, irrigation appeared to have had a marked
effect on spider populations.
The number of spiders was significant1y
higher on irrigated th an on nonirrigated peanut in five out of the eight
weeks investigated.
The differences in predator popu-1ations between
treatments were probab1y due both to a direct physica1 effect of
irrigation on spider populations and to its indirect effect through
promotion of a more luxuriant vegetative growth of peanut plants.
Kuenz1er (1958) found that the presence and success of three species of
spiders in a given site were enhanced by a re1ative1y high temperature
(>50 F) and high relative humidity.
Turnbu1l (1973) reported that, as
148
environmentally suitable niches become available for colonization by a
wide range of spider species. Indeed, Agnew and Smith '(1989) reported
that spider populations in peanut generally increase as the peanut
canopy increases, and that Lycosids are more successful in irrigated
pean ut while Misumenops spp. are most successful in nonirrigated peanut.
Irrigated peanut had a significantly greater y~eld, 5293 kg/ha,
than nonirrigated peanut, 4008 kg/ha.
This difference in yield can
probably be attributed not only to the effects of irrigation, but also
to differences in the insect populations reported above.
Differences in
thrips and corn earworm populations probably had little influence on
final yield.
Morgan et al. (1970), Tappan and Gorbet (1979), and Lynch
et al. (1984) reported that thrips did not significantly reduce the
yield of peanut. Similarly, ~ zea populations were substantially below
the economic threshold of 13.1 larvae/meter throughout the growing
season. However, lesser cornstalk borer and red-necked peanutworm
larvae were significantly higher in nonirrigated pean ut during the
critical pod-fill stage of plant development, i.e. From 55 to 97 days
after planting. Leuck (1966, 1967) reported that it is during this
growth stage that peanut is mostly damaged by the lesser cornstalk borer
in Georgia.
Lynch (1984) found that lesser cornstalk borer larvae
preferred peanut pods between the early to mid pad fill stages of plant
development.
Therefore, it is highly probable that feeding by lesser
cornstalk borer on pegs and pods had a negative impact on yield in non-
irrigated peanut.
Although red-necked peanutwarm infestations have been
reported to have little effect on yield (Walton and Guilavogui 1980),
their effect in the present study cannat be discounted.
The cambination
of red-necked peanut'dolin feeding on tenninals, lesser cornstalk barer
149
feeding on pegs and pods, and insufficient soil ~ater that delayed
plant development (Tables 5-7, 5-8, and 5-9) for the nonirrigated
peanut may have interacted to reduce yield by almost 25 percent.
Conversely, potato leafhopper populations were higher in irrigated
peanut and may have reduced yield for the this treatment.
However,
plants under irrigated conditions where soil water was not a limiting
factor would probably be better able to compensate for insect damage.
Conclusions
Results from this study showed that irrigation of peanut during the
period- ft~m peg formation to pod fill (from 40 to 103 days after
emergenc~) reduced lesser cornstalk borer larval infestations, although
the impact of feeding by lesser cornstalk borer larvae on peanut yield
could not be distinguished from the effect of drought in nonirrigated
plots.
Irrigation also reduced populations of thrips and red-necked
peanutworm larvae.
However, the greatest impact of irrigation on thrips
populations on peanut was primarily through promoting rapid leaf growth
and expansion, which consequently shortened the length of time leaflets
remained folded into terminals, thus reducing the overall period
terminals were suitable as feeding sites for thrips.
Since larvae of
the red-necked peanutworm also feed and develop within terminals, it is
probable that their populations were significantly lower on irrigated
peanuts for reasons similar to those mentioned above for thrips.
Irrigation had little effect on the number of larvae and adults of the
corn earworm.
Similarities between the number of ~ zea moths found in
both irrigation treatments were probably attributable to unrestricted
adult movement bet',veen experimental plots.
150
The number of the potato leafhoppers was significantly higher on
irrigated than on nonirrigated peanuts.
Irrigation, by promoting rapid
plant growth, produced more attractive sites for leafhopper feeding and
oviposition.
Irrigation had little effect on populations of big-eyed bugs,
fl?wer bugs, lady beetles, or nabids.
In contrast, significantly more
sp-iders were found -in irrigated th an in nonirrigated plots.
Irrigation
appeared to enhance the number of sites suitable for colonization by a
variety of spider species by promoting rapid canopy development.
Overall, irrigation reduced popu~~tions of thrips, red-necked
peanutworm, and the lesser cornstalk bor~r while it promoted increases
in populations of spiders which are major predators of various insect
pest species.
Thus, in addition to its purely physiological effect on
peanut growth and reproduction, irrigation has an impact on pest
populations and an important component in management programs for peanut
pests.
151
Table 5-1.
Rainfall and supplemental irrigation for Florunner
pean ut grown under irrigated and non~Trigated conditions in Tifton,
GA, 1986.
Rainfall
Days
Rainfall 1
Irrigation
plus
Sampling
after
irrigation
period
plarÏ'ting
(cm)
Date
Amount
(cm)
(cm)
June
1-30
12-4·1
12.37
12.37
July
1-30
42 -71
7.77
7/19
2.50
10.27
August 1-31
72-102
12.45
8/12
2.50
14.95
Sept.
1-30
103-132
2.49
9/23
2.50
4.99
Oct.
1-31
133-163
3.10
10/08
2.50
5.60
Total
38.18
10.00
48.18
l.
Rainfall as recorded on the Coastal Plain Experiment Station,
Tifton, Georgia.
152
Table 5-2.
Effect of irrigation on populations of tobacco thrips,
Frank1inie11a fusca (Hinds), infesting F10runner peanut, Tifton,
GA, 1986.
X no. thrips/ID termina1s l
/
Days
l'
Samp1ing
after
Immatures
Adults
date
p1anting
IRR 2
NIRR2
IRR 2
NIRR2
6/19
30
l4.24a
l7.44a
1.60a
1. 72a
6/30
41
lD.08a
Il. 24a
0.68a
1.48b
7/07
48
l8.92a
25.20b
1.32a
1. 24a
7/14
55
9.08a
9.80a
1. 92a
2.32a
7/21
62
9.64a
12.60a
2.12a
1.60a
7/22
69
4.6Da
12.52b
1.28a
1. 56a
8/04
76
1.68a
7.20b
0.80a
1. 96b
8/11
83
1.36a
5.40b
1.28a
2.00a
8/25
97
1.56a
1.84a
2.44a
2.44a
1.
Means within a samp1ing date and insect stage fo 11 o~'ed by the
same 1etter are not significant1y different (P = 0.05) using student's
t-test. Ana1ysis conducted with log (x+l) transformations.
2.
IRR = irrigated; NIRR = nonirrigated.
-"". '.-
153
Table 5-3.
Effect of irrigation on populations of Heliothis zea,
(Boddie), Stegasta bosquella Chamb.), and Elasmopalpus lignosellus
(Zeller) larvae infesting Florunner peanut, Tifton, GA., 1986 .
./
1"
Xno. lepidoptera larv~e/0.50m row1
Days
i.:.. bosqueella
L lignosallus
Sampling
after
date
planting
IRR2
NIRR2
IRR2
NIRR2
6/19
30
O.OOa
fl.ODa
O.OOa
O.OOa
0.36a
0.28a
6/30
41
0.28a
O.IZa
O.OOa
O.OOa
0.20a
O.56a
7/07
48
O.40a
O.64a
0.20a
0.32a
0.60a
O.72a
7/14
55
2.76a
1.24b
0.88a
0.96a
2.40a
2.72a
7/21
62
1.40a
O.28b
O.44a
1.00a
0.80a
2.08b
7/28
69
O.92a
1. 24a
1. 72a
2.36a
O.48a
1.12b
8/04
76
1.04a
1.40a
2.28a
8.48b
0.24a
1.40b
8/11
83
1. 44a
0.84a
0.56a
6.00b
0.24a
1.48b
8/25
97
0.04a
0.20a
1. 40a
6.24b
0.04a
0.16a
1.
Means within a sampling date and insect species followed by the
same letter are not significantly different (P = 0.05) using student's
t-test.
Analysis conducted with log (x+1) values transformations.
2.
IRR = irrigated; NIRR = nonirrigated.
154
Table 5-4.
Effect of irrigation on populations of adult Heliothis
zea (Boddie) and Elasmopal~us lignosellus (Zeller) infesting Florunner
peanut, Tif ton, GA., 1986.
X no. adults/10 sweeps1
Days
Sampling
after
L l ignosel1us
date
planting
6/30
41
O.OOa
O.OOa
O.OOa
0.04a
7/07
48
O.OOa
O.OOa
0.44a
0.28a
7/14
55
0.04a
o.16a
o.16a
0.36a
7/21
62
0.04a
O.OOa
0.80a
0.05a
7/28
69
0.28a
0.32a
0.60a
1.80b
8/04
76
1. 96a
0.64b
0.40a
1.36b
8/11
83
0.44a
0.36a
0.44a
0.44a
8/25
97
0.32a
0.28a
o.16a
0.16a
1.
Means within a sampling date and insect species followed by the
same letter are not significantly different (P = 0.05) using student's
t-test.
Analysis conducted with log (x+1) transformations.
2.
IRR = irrigated; NIRR = nonirrigated.
155
Tàble 5-5.
Effect of irrigation on populations of potato
leafhopper, Empoasca fabae (Harris), infesting Florunner peanut,
Tifton, GA, 1986.
/
l'
Days
Xno. nymphs/0.5m row l
X no~ adults/l0 sweeps
Sampling
after
date
planting
IRR2
NIRR2
6/19
30
0.52a
0.1.6b
O.OOa
O.OOa
6/30
41
1. 56a
1. 96a
1.20a
1.16a
7/07
48
2.00a
1. g4a
Il. 20a
3.88b
7/14
55
2.84a
1.20b
8.24a
8.00a
7/21
62
1.48a
O.84a
16.36a
5.40b
7/28
69
6.28a
o..12b
20.24a
5.16b
8/04
76
7.32a
1.04b
62.80a
7.76b
8/11
83
6.94a
0.76b
105.68a
6.28b
8/25
97
5.60a
1.68b
29.08a
19.00b
1.
Means within a sampling date and insect stage followed by the
same letter are not significantly different (P = 0.05) using student's
t-test.
Analysis conducted with log (x+l) transformations.
2.
IRR = irrigated; NIRR = nonirrigated.
Table 5-6.
Effect of irrigation on populations of predatory arthropods in Florunner peanut, Tifton, Ga.,
1986.
Mean number of predators/10 sweepsl
Geocoris
Orius
Hippodamia
Coleomegilla
Days
spp.
insidiosus
convergens
maculata
nabids 2
spiders
Sdrnpling
since
aa te
planting
l RR3
NIRR3
IRR3
NIRR3
IRR3
NIRR3
I:RR3
NIRR3
IRR3
NIRR3
IRR3
NIRR3
3
6/30
41
0.00a
O.OOa
O.OOa
O.OOa
0.08a
O.OOa
O.OOa
O.OOa
O.OOa
O.OOa
0.48a
0.36a
7/07
48
0.12a
0.16a
0.16a
0.12a
0.12a
0.04a
0.12a
O.OOa
O.OOa
0.08a
0.76a
0.88a
7/14
55
0.56a
0.56a
0.12a
0.32a
0.20a
0.12a
O.OOa
0.48b
0.32a
0.16a
1.08a
1.16a
7/21
62
0.32a
O.OOa
0.08a
0.32a
0.32a
0.16a
O.OOa
O.OOa
0.20a
0.08a
2.72a
1.60b
7/28
69
0.04a
0.44b
O.OOa
0.52b
0.12a
0.04a
0.08a
0.12a
0.08a
0.12a
2.56a
1.68b
8/04
76
0.12a
0.04a
0.68a
0.32a
0.04a
O.OOa
O.OOa
0.08a
O.OOa
0.16a
1.68a
0.84b
---..
~ ...
8/11
83
0.20a
0.44a
0.16a
0.56b
0.04a
0.08a
0.04a
0.04a
0.20a
0.16a
3.60a
1. 56b
8/25
97
0.28a
0.28a
O.OOa
0.16a
O.OOa
O.OOa
O.OOa
0.16b
0.24a
0.20a
6.08a
1.40b
1.
Means within a sampling date and arthropod group followed by the same letter are not significantly different
(P = 0.05) using students' t-test.
Analysis conducted with log (X + 1) transformation.
2.
Nabids = Reduvioius roseipennis and Tropiconabis capsiformis.
3.
IRR = irrigated; NIRR = nonirrigated.
........
(JI
0'1
157
Table 5-7.
Influence of irrigation on plant density, number of
pegs and pods for Florunner peanut, Tifton, GA., 1986.
Xno. jO.50 m row1
Days
Sampling
after
Plants
Pegs
Pods
date
planting
6/19
30
6.00a
5.90a
6/30
41
6.50a
6.00a
7/07
48
5.40a
4.30b
7/14
55
6.10a
5.50b
7/21
62
5.70a
4.26a
36.20a
10.00b
4.40a
O.OOb
7/28
69
4.90a
4.00b
36.50a
27.26
5.90a
0.40b
8/04
76
5.30a
3.90b
25.80a
21.70a
16.40a
8.90b
8/11
83
4.90a
4.20a
32.90a
29.80a
28.70a
18.10b
8/25
97
5.40a
3.40b
41.40a
28.00a
29.50a
19.20b
1.
Means within a planting date and plant structure followed by
the same letter are not significantly different (P = 0.05) using
student's t-test.
2.
IRR = irrigatcd; NIRR = nonirrigated.
158
Table S-8.
Influence of irrigation on fresh weight of Florunner
pean ut plants, Tifton, Ga., 1986.
X fresh weight (grams) /O.SOm row l
Days
Leaves
Pods
Top parts
Sampling
after
date
planting
IRR2
NIRR2
IRR2
NIRR2 " IRR2
NIRR 2
6/19
30
1~.17a
6.80b
18.17a
12.08b
6/30
41
19.5ôa
Il. 90b
38.48a
22.49b
7/07
48
32.83a
26.95b
63.S4a
51.86b
7/14
55
49.44a
38.44b
100.12a
78.89b
7/21
62
84.22a
42.79b
199.13a
94.44b
7/28
69
77.43a
58.99b
0.44a
O.OOa
221.69a
141. 74b
8/04
76
110.43a
75.86b
23.86a
5.52b. 288.83a
182.43b
8/11
83
119.96a
58.88b
30.92a 13 .06b
321.39a
157.41b
8/25
97
127.10a
77.40b
54.63a 25.39b
362.51a
212.94b
1.
Means within a sampling date and plant structure followed by
the same letter are not significantly different (P = 0.05) using
student's t-test.
2.
IRR = irrigated; NIRR = nonirrigated.
159
Table 5-9.
Influence of irrigation on dry weight of Florunner
peanut plants, lifton, -Ga., 1986.
Xdry weight(grams) /0.50m row1
!'
Days
Leaves
Pods
Top parts
Sa~~Ung
rftï f
p an 111g
IRR2
NIRR2
IRR2
NIRR2
IRR2
NIRR2
6/30
41
3.05a
3.15a
6.01a
5.07a
7(07
48
6.33a
4.93a
12.ô8a:
9.95b
7/14
55
12.39a
3.87a
20.70a
18.82b
7/21
62
14.52a
8.48b
32.41a
18.20b
7/28
69
14.52a
10.80b
0.02a
O.OOa
3'+-- 76a
24.31b
8/04
76
17.95a
13.46b
3.61a
0.56b
49.161
34.12b
8/11
83
19.50a
10.62b
10.60a
1.98b
63.30a
32.07b
8/25
97
26.94a
14.72b
18.45a
10.68b
88.46a
50.29b
1.
Means within a sampling date and plant structure followed by
the same letter are not significantly different (P = 0.05) using
student's t-test.
2.
IRR = irrigated; NIRR = nonirrigated.
-...1.
, -
160
LITERATURE CITED
All, J. N., R. N. Gallaher, and M. D. Jellum.
1979.
Influence of
planting dates, preplanting, weed control, irrigation, and
conservation tillage practices on efficacy of planting time
insecticide applications for control of lesser cornstaJk borer in
!
field corn.
J. Econ. Entomol. 72:265-268.
l'
Berberet, R. C. and F. Guilavogin.
1980.
Control of red-necked
peanutworm in non-irrigated peanuts.
Insecticide and acaricide
Test 5:141.
Boote, K. J. and L. C. Hammond.
1981.
tffect of drought on
vegetation and reproductive development of peanut.
Proc.
Amer. Peanut Res. Educ. Soc. 13:86 (Abstract.
Boote, K. J., J. A. Stansell, A. M. Schubert, and J. F. Stone.
1982.
Irrigation, water use, and water relations.
In H. E. Pattee
and C. T. Young (eds.).
APREA, Yoaku, Texas.
Delong, D. M.
1938.
Biological studies on the leafhopper Empoasca
fabae as a bean pest.
U.S. Dept. Agr. Tech. Bull. No. 618.
Fletcher, R. K.
1941.
The relation of moi sture content of the cotton
plant to oviposition by Heliothis armigera (Hbn.) and to survival'
of young larvae.
J. Econ. Entomol. 34:856-858.
Gaines, J. C.
1933.
Factors influencing the activities of the cotton
bollworm moth.
J. Econ. Entomol. 26:957-962. Henning, R. J.
1978.
Irrigation allows pean ut to develop predictably.
Southeast. Farm
Press 5(45):14.
Kuenzler, E. J.
1958.
Niche relations of three species of lycosid
spiders.
Ecology 39:494-500.
161
Lee, T. A., D. L. Ketring, and R. D. Pm'/ell.
1972.
Flowering and
growth response of pean ut plants (Arachis hypogaea L. Var.
Starr) at two levels of relative humidity.
Plant Physiology
49:190-193.
Leuck, D. B.
1966.
Biology of the lesser cornstalk borer in South
Georgia.
J. Econ. Entomol. 59:797-801.
Leuck, D. B.
1967.
Lesser cornstalk borer damage to pean ut plants.
J.
Econ. Entomol. 60:1549-1551.
Lewis, T.
1973.
Thrips, Their Biology, Ecology, and Economic
Importa~ce.
Acad. Press.
London, New York.
349 p.
Lynch, R. E.
1984.
Damage and preference of lesser cornstalk borer
(Lepidoptera: Pyral idae) 1arvae for peanut pods in different stages
of ~aturity. J. Econ. Entomol. 77:360-363.
Lynch, R. E., J. W. Garner, and L. W. Morgan.
1984.
Influence of
systemic insecticides on thrips damage and yield of Florunner
peanuts in Georgia.
J. Agric. Entomol. 1:33-42.
Martin, C. K. and F. R. Cox.
1977.
Effect of water stress at different
stages of growth on peanut yields.
Proc. Amer. Peanut Res. Educ.
Assoc. 9:91 (Abstract).
McCloud, D. E.
1973.
Growth analysis of high yielding peanuts.
Soil
and Crop Science Soc. Fla. Proc. 33:24-26.
Metcalf, C. L., W. P. Fl"int, and R. L. Metcalf.
1962.
The potato
leafhopper.
Pp. 411-457.
In Destructive and Useful Insects.
McGraw-Hill Book Co., New York.
1087 p.
l"1organ, L. W., J. \\~. Snow, and M. J. Peach.
1970.
Chemical thrips
control; efFects on grm'/th and yield of peanuts in Georgia.
J.
Econ. EI1 Ul111l) 1. 63: l253 -l255.
162
Pallas, J. E., Jr., J. R. Stansell, and T. J. Koske.
1979.
Effects of
droug~t on Florunner peanuts. Agron. J. 71:853-858.
Slossmen, J. E.
1980.
Irrigation timing for bollworm management in
·cotton.
J. Econ. Entomol. 73:346-349.
Snow, J. W., W. W. Cantelo, and M. C. Bowman.
1969.
Distribution of
the/corn earworm on St. Croix, U.S. Virgin Islands, and its
l'
relation ta suppression programs.
J. Econ. Entomol. 62:606-611.
Stansell, J. R. and J. E. Pallas, Jr.
1985.
Yield and quality response
of Florunner pean ut ta applied drought at several growth stages.
Peanut Sci. 12:64-70.
. .'
Riechert, S. E. and T. Lockley.
1984.
Spiders as biological control
agents.
Ann. Rev. Entomol. 29:299-320.
Tappan, W. B. and D. W. Gorbet.
1979.
Relationship of seasonal thrips
populations ta economics of control or. Flcrunner peanuts in
Florida.
J. Econ. Entomol. 72:772-776.
Tappan, W. B. and D. W. Gorber.
1986.
Effect of irrigation and
parathion granule applications on various peanut insect pests.
J.
Agric. Entomol. 3:68-76.
Turnbull, A. L.
1973.
Ecology of the true spiders (Aroneomorphae).
Ann. Rev. Entomol. 18:305-348.
Waller, R. A., and D. B. Duncan.
1969.
A Bayes rule for the symetric
multiple comparison problem.
J. Amer. Stat. Assac. 64:1684-1699.
Walton, R. R. and R. Matlock.
1959.
A progress of studies of the
red-necked peanutworm in Oaklahoma.
Oklahoma Ag. Exp. Sta. Proc.
Series.
P. 320.
163
Young, J. H. and R. G. Priee.
1968.
Effect of irrigation and
submersion in water on pupal survival of the bollworm.
J. Econ.
Entomol. 61:959-961.
/
r
VI.
INFLUENCE OF INSECTICIDE APPLICATION REGIMES ON PEANUT
1
AND PEANUT ARTHROPODS
1Idrissa O. Amirou and Robert E. Lynch.
1989.
To be submitted to
J. Economie Entomol.
164
ABSTRACT
The effects of aldicarb applied at planting and combined multiple
applications of aldicarb, lannate, and chlorpyrifos on pest and
beneficial arthropod populations were investigated on pean ut in 1987 and
1988, at Tifton, Georgia.
The tobacco thrips, Frankliniella fusca
(Hinds), and potato leafhopper, Empoasca fabae
(Harris), were
effectively controlled for several weeks by single application of
aldicarb at planting.
Multiple applications of methomyl gave adequate
con~rol of Heliothis zea (Boddie) larvae.
However, under the pest
insect pressures encountered in this study, insecticide treatments did
not significantly increase pean ut yield in either year. These results
suggest that, in most years in Georgia, insecticide applications may not
be required for pest insect control to obtain excellent peanut yields.
Populations of predaceous arthropods, including Geocoris spp., nabids,
and spiders, were reduced by all insecticide treatments, but their
populations were significantly lower only in plots receiving multiple
chemical treatments, as compared to untreated plots.
Although predator
populations were not reduced significantly in aldicarb-treated plots, tl.
zea larval populations were significantly higher in these plots than
they were in untreated plots.
Therefore, it appears that factors other
than reductions of predators were responsible for the increases in
corn earworm larvae in treated plots.
Aldicarb promoted a more
luxuriant growth of peanut foliage which probably made treated plants
more attractive to tl. zea moths for oviposition.
165
Insecticides are probably the most effective, dependable, and
economical tool currently available for insect pest control.
Knipling (1979) noted that the use of insecticides gives the farmer a
means for controlling pests regardless of the actions of his neighbors
or the number of pests in insect populations.
Luck et al. (1977)
reported that 70% of crops produced in the United States could not be
successfully grown without insecticides, and that those crops which
could be.9rQwn without insecticides would suffer enough losses to
increase food prices by 50-70%.
Morever, when pest populations
approach economic levels, there is little, other than pesticides, that
can be used to avoid immediate crop damage (Smith 1970).
These
arguments, among several others, have lead to the reliance on
insecticides as the sole, or principal, means for controlling most
insect species on various crop plants.
However, these authors also
suggested a more holostic approach to the management of pests that
would reduce reliance on insecticides.
Chemical insecticides are also the major method for contolling
insect pests on peanut (Tappan and Gorbet 1986).
Results of field
tests on chemical control of a single insect species on peanut have been
extensively reported
(Texas- Smith et al. 1975, Sams and Smith 1979;
Oklahoma- Berberet 1978, Berberet and Guilavogui 1980; Alabama- Arthur
and Arant 1954, Arthur et al. 1959; Florida- Tappan and Gorbet
1979, 1981; Georgia- French 1973, Lynch et al. 1984).
However,
information on the effect of insecticides on the entire peanut pest
lô6
167
and beneficial arthropod complex is generally lacking.
Similarly, the
potential impact of larvicides on adult populations of these pests has
not been investigated.
In addition to a direct killing power, several insecticides also
indirectly affect pest populations through their impact on ho st plant
growth.
?ariola et al. (1971) reported that bollworm populations in
aldicarb 1treated cotton plots were significantly greater than those in
untreated plots.
Kinzer et al (1977) also found that Heliothis zea
(Boddie) moths prefer to oviposit on cotton treated with aldicarb and
monocrotophos than on untreated cotton.
Bradley et al. (1987)
suggested that the ovipositional preference of h. zea and H. virescens
(F.) for cotton treated with organophosphate and carbamate
insecticides was derived from the attractiveness of luxuriant foliage
and delayed maturity of crops treated with insecticides.
Similarly,
corn earworm moths prefer to oviposit on s0ybean treated with aldicarb
compared with nontreated soybeans (Morrison et al. 1979).
On peanut,
however, no such effect has been investigated or reported.
Toxicity to beneficial arthropods is one of the undesirable side
effects of insecticide use.
Newsom (1967), however, noted that there is
no reason to assume that the effects of insecticides should be any
different on beneficial than on pest species since the term "pest" is
merely a human concept with no biological meaning.
However, in many
instances, natural enemies appeared to be more susceptible to pesticides
than phytophagous pests.
Croft and Brown (1975) reported that while
more than 224 cases of insecticide resistance are known for pests, only
10 have been reported for natural enemies.
These authors hypothesized
that since one or nlore stages of a b~neficial insect must search out
168
prey or host, they would be more likely to pick up high quantities of
pesticides and thus, suffer greater mortality from insecticidal
residues than would sedentary insect pest species.
Most of the
evidence for insecticide toxicity to beneficial insects has been
obtained from studies on cotton (Ridgway et al. 1967, Cate et al.
1972, Plapp and Vinson 1977), soybean (Gree~ et al. 1974, Farlow and
Pitre 1983), and tobacco (Elsey and Cheatum Î l976, Plapp and Bull 1978,
Semtner 1979).
In contrast, few attempts have been made to
investigate the effects of pesticides on the number or species of
natural enemies associated with peanut.
Only studies by Smith and
Jackson (1975) and by deRivers (1980) have addressed the effects of
pesticides on beneficial arthropods in peanut.
The objectives of this study were : (1) to quantitatively evaluate
the impact of insecticide applications on populations of pest and
beneficial arthropods on peanut; (2) to investigate the possible effect
of larvicides on adult populations of pest species; and (3) to assess
the potential influence of insecticides on growth of peanut plants.
Materials and Methods
Experimental Plots
The studies were conducted at the Bellflower Farm, near the Coastal
Plain Experimental Station, Tif ton, GA, in 1987 and 1988.
Florunner
peanuts, Arachis hypogaea L., were planted on June 4, 1987, and June 2,
1988, at a rate of 113 kg of seedsjha.
During bath years, the
experiment was designed in a randomized complete black with three
treatments, each replicated six times.
Replicates were ca. 40 m long
and 15 m '.'Ji dl~ •
rreat 111~ nt s 'o'iere: 1.
Che rn ical che ck: al dicar b appli ed at
169
0.84 kg a.i/ha in-furrow at planting and banded over-the-row at biweekly
intervals through mid-July; methomyl applied to foliage as weekly sprays
at 2.34 1 a.i./ha from mid-July through early September; and
chlorpyrifos applied over-the-row at 2.18 a.i./ha from early July
through late August; 2. treated: aldicarb applied at planting and
methomyl or chlorpyrifos applied only when economic threshold were
reached (rates as above); 3. untreated: no insecticides.
Aldicarb and
chlorpyrifos were applied with chain driven bicycle granular
applicator which was calibrated to deliver the appropriate rates.
Methomyl was applied using an Airplot bicycle sprayer which delivered
"ca. 62.31 1 spray solution/ ha.
Samoling Methods
Arthropod populations were monitored weekly from late June to
early September by taking terminal, flower, whole plant and sweep net
samples (for a detailed description of these samples, see Chapter III).
Most collected insect species were identified by Dr. Cecil Smith at the
University of Georgia's Museum of Natural History.
Thrips species were
identified by Mrs. Ramona Beshear, Georgia Experiment Station, Griffin,
Georgia.
Dr. Henry Townes, at the American Entomological Institute,
Gainesville, Florida, identified most parasitoid Hymenoptera.
Plant Data
The following plant data were recorded weekly: (1) number of
plants, pegs, and pods / 0.5 m of row sample; (2) fresh weight of leaves
and stems, and pods/plant; (3) dry weight of leaves and stems, and
pods/plant.
Dry weight for each of the above plant structures was taken
after plants were dried for ca. 24 hours at 100-140 f.
170
Statistical Analysis
Prior to actual data analyses, univariate analysis was conducted
on weekly arthropod and plant parameters to determine their frequency
distributions.
Unlike data From plants, data for arthropod
populations did not generate normal distribution curves.
Therefore,
tnsect data were transformed to log (x+l) to normalize their frequency
distribution and stabilize the variance.
Transformed insect data and
nontransformed plant data were then analyzed by one-way analysis of
variance, and significantly different weekly means were separated
using Waller-Duncan's multiple ranga·Te~t (Waller and Duncan, 1969).
Results and Discussion
Arthropods From Il orders were collected during the two year study.
These orders included Il families Gf insect pest species, 10 families of
predaceous arthropods, and two families of parasitoid Hymenoptera (see
Chapter III, Tables 3-3 and 3-4).
However, sufficient data for valid
statistical analyses were available only for the following : (1) pest
species, including tobacco thrips, Frankliniella fusca (Hinds), red-
necked peanutworm, Stegasta bosqueella (Chambers), corn earworm, lesser
cornstalk borer, Elasmopalpus lignosellus (Zeller), and potato
leafhopper, Empoasca fabae (Harris); (2) arthropod predators, includi~g
big-eye bugs, Geocoris spp., insidiosus flower bug, Orius insidiosus
(Say), nabids, Reduviolus roseipennis Reuter and Tropiconabis
capsiformis (Germar), and spiders; (3) parasitoids , including
Microplitis croceipes (Cresson), Cardiochiles nigriceps Viereck,
Pristomerus spinator (F.), Netelia heroica Townes, and Meteorus sp ..
Ccnsidered separately, howev~r, data for most of the predators and
171
parasitoids were insufficient for statistical comparisons and therefore,
were combined and analysed as spider~, total predators, and total parasitoids.
Insect Pests
During both years, single (treated) as well as multiple
(chemical ckeck) applications of aldicarb significantly reduced
populations of immature thrips in terminals for ca. 6-8 weeks (Table 6-
1).
Aldicarb treatments in both tteated and chemical check plots
provided a slighly longer control in 1987 than 1988.
Thrips populations
in untreated plots were also appreciably higher in 1987 than in 1988
(Table 6-1).
The shorter period of control observed in 1988, ca. 5-6,
weeks after plant emergence in treated plots, was similar to data
presented by Rohlfs and Bass (1980), Tappan and Gorbet (1981), and Ly~ch
et al. (1984).
Multiple chemical applications significantly reduced immature
thrips populations in chemical check plots throughout the sampling
period for both years.
However, significant control of immature thrips
from mid-July through the remainder of the growing season may have
resulted from the combined effect of aldicarb and methomyl.
Rohlfs and
Bass (1980) found that peanut plants treated with methomyl had
significantly fewer thrips than untreated peanuts.
Control of adult thrips in terminals, by applying aldicarb at
planting or by multiple applications of aldicarb plus methomyl during the
growing season, was not consistent either within or between years and few
weekly significant differences were recorded (Table 6-2).
Tappan (1986)
listed several factors as possible sources which can lead to variation
in adult thrips populations in flowers, e.g. migration from plants
outside the study area or From <1dj1unt plants, 1~10'lement From hiding
172
places on or in the soil and on the plants.
Migration of thrips results
in reinfestation of terminals by adult thrips in untreated or treated
plots, and therefore, produce inconsistent experimental results,
depending mostly on dates thrips are sampled.
Thrips damage was significatly less in pean ut for all chemical
treatmen~s than in untreated plots (Table 6-3).
During both years, the
degree of foliage damage showed an inverse relationship to the number of
insecticide applications.
These results agree with Minton and Morgan
(1974) and Tappan and Gorbet (1981) who also found that aldicarb applied
to peanut at planting significantly reduces the6)ercent foliage injury
by thrips for ca. 80 days after planting.
Neither aldicarb applied at planting, r~r m.ultiple applications of
aldicarb, methomyl, or chlorpyrifos had any effect on populations of red-
necked peanutworm in terminals (Table 6-4).
Arthur et al. (1959)
reported successful chemical control of â. bosqueella on peanut.
However, reports have shown that most available insecticides give poor
control of this insect (Berberet 1978, Berberet and Guilavogui 1980).
Berberet (1978) speculated that failure of insecticides to control the
red-necked peanutworm is due to concealment of larvae within plant
terminals.
Heavy infestations of â. bosqueella cause foliage damageing from
scarring of the surface of folded terminal leaflets, to stunting and
retarding terminal growth due to larval feeding on the meristematic
regions of buds (Walton and Matlock 1959, Wall and Berberet 1979).
However, as shown in Table 6-4, infestation levels in all treated and
untreated plots were far less than the 1 larva / terminal that was
r ep0 ft ed bY ',.J al ton .:; t .11. (l 959 ) and ',h 11 and G0 (b eret (1 979) .
173
During the two year study, the number of li. zea larvae 125 sweeps
was significantly lower on most sampling dates in chemical check plots
than in other plots (Table 6-5).
The effective control of corn
earworm larvae in the check plots was probably due to the multiple
applications of methomyl, rather than to the use of other
insecticides, since McClanahan (1982) and ~olfenbarger et al. (1987)
found that larvae of corn earworm are highl~ susceptible to both oral
and topical applications of methomyl.
Excellent control of li. zea
with methomyl has been reported on peanut (Berberet 1979) and tomato
(Kennedy et al. 1987).
A significantly greater number of corn earworm larvae were noted
on plants that received a single application of aldicarb at planting
than plants in untreated plots (Table 6-5).
However, the' number of
larvae in aldicarb-treated plots were significantly higher than
untreated plots only on two sampling dates in 1987 and on three dates in
1988.
Methomyl was applied to treated plots on July 22, 1987, to control
corn earworm larvae, and may have confounded the suspected increase in
corn earworm populations as a result of aldicarb application at
planting.
However, methomyl was not applied in 1988 and, as in 1987,
significantly higher corn earworm larval populations were again noted on
the aldicarb-treated peanuts.
Although similar results have been
reported for other crops, this constitutes the first report for pean ut
where plants treated with aldicarb at planting sustained significantly
greater corn earworm populations than did untreated plots.
Rummel and
Reeves (1971) reported that the number of bollworm larvae was greater
in aldicarb-treated than untreated cotton, while little differences
beLieen the .lVerage nlli~lbcr of predc1CeOLJS arthropods \\'Iere noted for
174
treated and untreated plots.
Kinzer et al. (1977) also obtained
similar results on cotton, and postulated that moths preferred to
oviposit on the cotton treated with aldicarb which had greener, more
luxuriant vegetative growth than untreated cotton.
Morrison et al.
(1979) found that aldicarb treated soybean plots contained up to 7
times more H. zea larvae than untreated plots or plots treated with
other soil-applied pesticides.
The effect of soil-applied aldicarb on vegetative growth of peanut
has been reported by Minton and Morgan (1974), Tappan and Gorbet (1981),
and Lynch et al. (1984), all of whom reported that plants in plots
treated with aldicarb grew more rapidly than plants in untreated plots.
Data on leaf and stem
weights in the present study (Table 6-14)
generally agree with these findings.
Thus, as was reported for cotton,
higher H. zea larval populations in aldicarb-treated plots were probably
a result of aldicarb controlling thrips and stimulating vegetative
growth of pean ut plants.
Damage to pean ut foliage due to feeding by H. zea larvae was
significantly less in chemical check plots than plots receiving single
application of aldicarb or untreated plots (Table 6-3).
Larval damage
in both aldicarb-treated and untreated plots was comparable in 1987, but
damage was significantly less in treated than untreated plots in 1988.
The difference in damage between the two years was probably due to
slightly higher larval pressure in 1987 than in 1988.
Although the number of corn earworm moths were lower in chemical
check plots than in the other plots, significant differences in the
number of moths / 25 sweeps were noted on only two sampling dates in
1987 ~h8n treateJ plots had signlflcantly mOl'e maths than the chcmical
176
either rainfall or irrigation (Thomson 1983).
Plant damage in both
the treated and chemical check plots was significantly less th an
damage in untreated plots (Table 6-3).
Multiple insecticide
treatments signifi-cantly reduced damage by f. fabae in chemical check
plots in 1987, but not in 1988.
No significant reductions in lesser cornstalk borer (LCS)
larval populations resulted'from insecticide applications in treated or
chemical check plots (Table 6-8).
These results generally agree with
Harding (1960) and Sams and Smith (1979) who also found that
applications of several granular insecticides, including chlorpyrifos,
gave p06r to erratic control of lesser cornstalk borer populations on
peanuts grown under dryland conditions.
All (1980) postulated that
inconsistent control of LCS is often related to water content of the
soil at the surface which is needed to move the insecticide from the
granule into the soil for subterranean insect control.
The number of
LCS larvae was significantly lower in untreated plots than in treated or
check plots on several sampling dates (Table 6-8).
Data from sampling
dates indicate that the number of larvae was positively correlated with
the number of insecticide applications.
Although such positive
relationships could depict a LCS population release caused by the effect
of insecticides on beneficial arthropods in treated and chemical check
plots, these results may be more plausibly explained by the extreme
variability and paucity of data often associated with sampling field
populations of the LCS.
Significant differences among plots in the
number of LCS moths occurred on three occasions in 1988 (Table 6-9).
However, the mean number of moths was low and the differences noted were
probably not meaningful.
177
Predators and Parasites
Populations of big- eyed bugs (Geocoris spp.), nabids (Reduviolus
roseipennis Reuter and Tropiconabis capsiformis [Germar] ), insidiosus
flower bug ( Orius insidiosus [Say] ), lady beetles, and stapyhlinid
beetles were very low in all plots.
Only spiders occurred in popula-
tions that might be expected to impact pest populations.
Thereforel
predators were analyzed for spiders and for all predators combined,i'
including spiders.
A single application of aldicarb at planting (treated plots) for
control of early season peanut pests and lannate in July applied for
control of corn earworm larvae in 1987 significantly reduced spider
populations on six of eight sampling dates in 1987 and on three of eight
sampling dates in 1988 (Table 6-10).
However, during both years, weekly
samples indicated that spiders were generally more abundant in untreated
plots than in treated plots.
Other authors have reported inconsistent
reductions in the number of spiders in plots treated with aldicarb
(Ridgway et al. 1967, Laster and Brazzel 1968, Caron 1981, Lentz et al.
1983, Bradley et al. 1987).
Multiple applications of insecticides significantly suppressed
spider populations in chemical check plots on 14 of the 16 sampling
dates, as compared to untreated plots.
Comparisons between treated and
chemical check plots showed intermediate results with significantly
lower spider populations in the chemical check plots on eight of the 16
sampling dates.
Agnew and Smith (1989), in a community composition
study, found that hunting spiders made up 85.8% - 91.7% of the spider
fauna in three peanut fields.
These spiders, often referred to as
vagJbond spiders, are very active and are known ta search out
178
desirable prey species over a relatively wide area (Turnbull 1973).
Such activity is likely to cause spider reinfestation of treated
plots.
Methomyl has also been reported to be only moderately more
toxic to spiders than to other predators frequently encountered
in
cropping systems (Turnipseed et al. 1975), and may also have partially
./
caused the lack of difference in spider populations between treated
r
and check plots.
Results of this study indicated that the application of aldicarb
and the combined applicatio~s of aldicarb, methomyl and chlorpyrifos
reduced the total number of predators during both years (Table 6-11).
For most sampling dates, the number of predators was inversely related
to the number of insecticides applied and the number of times the
insecticides were applied.
Total number of predators was
significantly lower in treated plots than in untreated plots on 10 of
the 16 sampling dates.
Similarly, the total number of predators was
significantly lower in the chemical check plots than in untreated
plots on 14 of the 16 sampling dates. Thus, applications of
insecticides such as aldicarb, methomyl and / or chlorpyrifos for
control of both early peanut pests and pest species occurring later in
the season negatively affected populations of total predators found in
the peanut agroecosystem.
Kinzer et al. (1977) reported similar data
on the effects of applications of aldicarb and combined applications
of aldicarb and monocrotophos on predator populations in cotton.
In 1987 and 1988, populations of parasites were consistently
(Table 6-12).
However, with one exception, no significant reductions in
the number of wasps was observed among plots, even from mid-August to
early September wh2n populations of parasites p~Jked.
The one exception
179
was when significantly fewer parasites were collected on August 29,
1988 From chemical control plots than From either untreated or treated
plots.
Croft and Brown (1975) reported that some of the ways
insecticides exert their .lethal effects on parasites is indirectly
through destruction of host insect populations.
Plapp and Vinson
,
(1977), in a comparative/toxicity study on several classes of
insecticides, found that' hydrolytically metabolized stomach poisons,
i.e., most systemic insecticides, were much less toxic to ithneumonid
parasites than contact insecticides which are detoxified primarily by
oxidative processes.
These factors may explain the similariti~~ in
the number of wasps between untreated and treated plots.
As rfported
earlier, applications of aldicarb alone appreciablyincreased
populations of ~ zea and 1. lignosellus
larvae which, in turn, may
have attracted greater number of parasitoid females.
This increased
number of host larvae in treated plots probably compensatedsomewhat
for any depressive effect that aldicarb may have had on wasp
populations.
In contrast, the reduction in the number of
lepidopterous larvae, caused by multiple applications of insecticides,
probably added the direct effect of insecticides, mainly lannate, on
parasitoid populations in chemical check plots.
Plant Populations, Growth, and Yield
The effect of insecticides on number of plants and production of
flowers, pegs and pods are presented in Table 6-13.
Significant
differences were noted in plant populations among treatments on several
dates, but a general trend that might indicate greater losses in a
particular treatment could not be ascertained.
...... .
...
~
-~
180
Differences among treatments in the number of f10wers was detected
on1y among the August 4, 1987 samp1es (Table 6-13) when plants in
untreated plots had significant1y fewer flowers than did plants in
treated or chemical check plots.
Several insects feed in or on flowers.
Thrips have been 1inked to kee1 damage and death of flowers (Hammons and
Leuck 1966) and the corn earworm larvae, especia11y the 7arlier instars,
have been observed feeding in or on f10wers.
However, cprn earworm
populations were higher in the treated plots than populations in
untreated plots and no s;gnificant differences were noted in the number
of thrips/ 10 termina1s in the August 4, 1987 samp1es.
Therefore, the
differences noted were probab1y due to advanced stage of growth for
peanuts in the treated plots and chemical check plots as a result of
both excellent thrips control and enhanced growth by a1dicarb.
Morgan
et al. (1970) a1so observed that several 'insecticides, inc1uding
a1dicarb, gave significant control of thrips, but had 1itt1e effect on
the number of f1owers/p1ant.
Peg and pod production differed significant1y among treatments most
of the growing season (Table 6-13) in both years.
From mid-June through
late July, peg production was significant1y greater in treated plots
than peg production in other plots, and peg production in untreated
plots was significant1y greater than production in chemica1 check plots.
Differences between untreated plots and treated plots can probab1y be
attributed to a1dicarb in treated plots which contro1led thrips and
stimu1ated plant growth.
However, it appears that multiple applications
of aldicarb actua11y retarded peg production ear1y in the growing
season.
From ear1y August through the remainder of the season, plants
in the untreat8d ,wd chemica1 check plots compens:lt2d for the de1ayed
181
peg production and generally produced significantly more pegs than did
plants in treated plots.
However, increased peg production did not always result in
increased pod production (Table 6-13).
Pod production also varied
considerably between years and no general trends were evident that
could be related to insecticides.
However, as with peg production,
plants in plots that produced fèwer pods early in the growing season,
tended to compensate by producing more pods later in the growing
season.
Mean fresh plant and pod weight as influenced by insecticides and
insect control' are presented in Table 6-14.
Weights were variable
among treatments and between years.
In 1987, fresh plant weight was
signifi-cantly heavier for plants From untreated than weights for
plants from treated or chemical check plots for the first two sampling
dates.
0.1 the 3rd and 4th sampling dates, in 1987, fresh plant
weights were significantly higher for plants from the chemical check
plots than weights for plants From the other two treatments.
However,
by August Il, 1987, fresh plant weights were comparable among
treatments and generally remained equal throughout the remainder of
the season.
In 1988, fresh plant weight in the untreated and/or
treated plots tended to be greater than weights for plants in the
chemical check plots through early August.
As in 1987, plant weights
were comparable among treatments beginning in early- to mid-August.
The effect of aldicarb on vegetative growth of peanut has been
reported by Minton and Morgan (1974), Tappan and Gorbet (1981),
and Lynch et al. (1984), all of whom reported more rapid growth for
plJnts From alJjcJl'b-treat~d plots.
Data on leaf and stem weights in
182
the present study ~ere variable, but generally agree with these
findings.
Significant differences were also noted among treatments in fresh
pod weights (Table 6-14).
In general, fresh pod weights tended to be
highest for plants From untreated plots, followed by pods in treated
plots.
This 7rend was noted in five of the eight observations
recorded during the two years.
Dry weights for stems and leaves and for pods (Table 6-15) tended
in general to parallel those of fresh plant and pod weights.
As with
fresh plant weight, dry plant weight was initiall! g~eatest for
untreated plants, but as thrips damage slowed thede~elopment of
untreated plants, dry weights were generally lower for plants From these
plots.
However, plants From untreated plots increased in vegetative
growth after thrips populations declined and, byearly- to mid-August,
their dry weights were comparable among all
treatments.
Few significant differences were noted in dry pod weights during
both years of the research.
In August 1987, pod dry weight was
significantly heavier for plants From the chemical check plots than
weights From the other two treatments.
However, in subsequent samples
in 1987, no significant differences were detected among treatments.
Conversely, in 1988, no differences were noted among treatments in dry
pod weights for the first two pod samples.
However, pod dry weights for
plants From untreated and treated plots were significantly greater than
dry pod weights for plants From the chemical check plots during the last
two sampl ing dates.
183
Yields of Florunner peanut as a result of insecticide application
and insect control is presented in Table 6-16. No significant
differences were recorded among treatments in 1987.
But in 1988, yield
was significantly greater from treated and untreated plots than they
were from the chemical check plots.
Apparently, multiple applications
of insecticides, while providing excellent insect control, adversely
l'
affected reproduction in 1988 resulting in lowei yields.
Interestingly, final yields were accurately predicted by dry pod
weights obtained as early as late August in both years.
The
failure of insecticidal ~pplications to result in increased peanut
yield also has been observed by Morgan et al. (1970), Tappan and
Gorbet (1981), and Lynch et al. (1984).
Minton and Morgan (1974)
found that peanut yield increase as a result of applications of
granular soil insecticides was often a result of effective control of
soil pathogens, i.e., nematodes and fungi, than control of insect
pests.
French (1973), in pilot pest management studies in Georgia,
showed that three out of four insect pest management demonstrations
made excellent yields of peanuts without insecticide application, and
only one application of insecticide was needed in the 4th
demonstration.
Correlation coefficients in Table 6-17 show that
results in the present study support findings by French (1973) in that
no significant correlation (P=O.OS) was found between insect pests and
leaf and stem and pod dry weights.
Conclusions
Results from this research indicate that application of aldicarb at
planting provide excellent contl'ol of thrips and patato leaf-hopper on
184
peanut From early- to mid-season.
However, control of other pests by
aldicarb was ineffective.
In addition to reducing populations of early-
season insect pests, combined applications of aldicarb, methomyl, and
chlorpyrifos also significantly suppressed populations of the corn
earworm but had little effect on larval populations of the red-necked
peanutworm, lesser cornstalk borer, or adult corn earworm, due primarily
to concealed larval feeding habitats and/or adult movement among plots.
Application of aldicarb resulted in increased populations of the corn
earworm larvae in treated plots.
Based primarily on inferences from
l?af weight data (Table 6-14 and 6-15), the relatively higher number of
corn earworm larvae in treated plots was the result of aldicarb
stimulating early vegetative growth of the plants.
The production of
luxuriant, undamaged foliage by peanut plants treated at planting with
aldicarb rendered them more attractive for oviposition by corn earworm
moths.
This is the first report that an interaction between peanut
with a systemic insecticide results in an increase in populations of
tl. zea larvae.
These data also indicate that effective control of several pest
infestations and damage levels observed in this study did not
significantly increase pean ut yield.
Thus, in most years, infestation
levels of insect pests in Georgia may not necessiate insecticide
applications to obtain excellent peanut yield.
Results From these studies also show that insecticides applied to
peanut were detrimental to populations of predators such as Geocoris
spp., nabids, and spiders.
On most dates, however, the number of
preJators did not significantly differ between untreated and aldicarb-
tn~dL;d peln1lt.
SiniLlrly, application of alJicarb alone had no
185
noticeable effect on populations of parasitoids.
Thus, these findings
also lend support to the suggestion that increased H. zea larval
populations in aldicarb-treated plots was due more to the effect of the
chemical on peanut plants than to its effect on populations of
.
predators.
Conversely, multiple applications of insecticides lead to
significant reductions of beneficial arthropod populations.
/
Overall, these data suggest that proper implementation of "
successful Rest management programs in peanut should be based on proper
monitoring of insect pest levels and on the acceptance of the fact that
undesirable pests are often not economically jmportant pests.
Failure
to properly monitor pest and beneficial arthropod levels may lead to
unneccessaryuse of insecticides with all the classic consequences,
including monetary loss, destruction of beneficial arthropods, and
resurgence of pest populations.
186
Table 6.1.
Effect of insecticides on populations of tobacco
thrips, Frankliniella fusca (Hinds), immatures in Florunner
peanut, Tif ton, GA., 1987-1988.
Days
Xno. immature thrips/10 terminals 1
Year
Sa~~Ung
rftF
p an l ng
Untreated
Treated 2 Chem. check3
1987
6/30
26
47. na
17 .83b
8.43c
1988
6/27
25
59.57a
11. 03b
1987
7/07
33
57.20a
29.43b
18.63c
1988
7/05
32
39.53a
26.13b
13.63c
1987
7/14
40
17.86a
11.47b
9.50b
1988
7/12
39
15.50a
7.70b
9.60b
1987
7/21
47
40.03a
24.73b
14.37c
1988
7/18
45
7.53a
6.73a
3.73b
1987
7/28
54
25.03a
18.80b
4.37c
1988
7/25
52
5.80ab
6.83a
4.53b
1987
8/04
61
6.40b
10.10a
1.63c
1988
8/02
59
4.53a
2.83a
4.37a
1987
8/11
68
3.20a
2.93a
0.70b
1988
8/08
65
1.
Means in rows and within a sampling date followed by the same
l etter are not significantly different (P=0.05) using Waller-Duncan's
multiple range test on log (x+1) values.
2.
Aldicarb 0.84 kg/ha, applied at planting and methomyl. 2.34
l/ha applied on 7/22, in 1987.
3.
Aldicarb, 0.84 kg/ha, applied at planting and biweekly
From mid-June through mid-July; methomyl. 2.34 l/ha, appl ied weekly
From mid-July through early September; chlorpyrifos, 2.18 kg/ha,
applied in a band over-the-row at weekly intervals From early July
through late August.
187
Table 6.2.
Effect of insecticides on populations of tobacco
thrips, Frankliniella fusca (Hinds), adults in Florunner
peanut, Tifton, GA., 1987-1988.
/Days
Xno. adult thrips/10 terminals 1
sa~~Ung
Year
.. rftF
p an 1 ng
Untreated
Treated
1
2
Chem. check3
1987
6/30
26
1.80b
3.17a
1. 27b
1988
6/27
25
2.03a
3.13a
1987
7/07
33
3.20a
3.13a
2.63a
1988
7/05
32
2.50a
1. 37b·
2.10ab
1987
7/14
40
3.16a
3.27a
1.83b
1988
7/12
39
2.33a
1.70a
2.50a
1987
7/21
47
4.47a
3.10ab
1.87b
1988
7/18
45
0.83a
0.903
0.63a
1987
7/28
54
2.43a
2.27a
0.70b
1988
7/25
52
1.10a
0.57b
0.6üb
1987
8/04
61
1.23b
2.57a
1.2üb
1988
8/02
59
0.90a
1. 23a
1. 53a
1987
8/11
68
2.10a
1.87a
0.80b
1988
8/08
65
1.
Means in rows and within a sampling date followed by the
same letter are not significantly different (P=0.05) using Wall er-
Ouncan's multiple range test on log (x+1) values.
2.
Aldicarb, 0.84 kg/ha, applied at planting and methomyl, 2.34
l/ha applied on 7/22, in 1987.
3. Aldicarb, 0.84 kg/ha, applied at planting and biweekly from
mid-June through mid-July; methomyl, 2.34 l/ha, appl ied weekly from
mid-July through early September; chlorpyrifos, 2.18 kg/ha, applied
in a band over-the-row at weekly intervals from early July through
l ate August.
188
1.
Damage based on a visual rating on a 1-9 scale where
1 = no damage, and 9 = plant death due to severe stunting (thrips)
or complete defoliation (corn earworm).
Means in columns followed
by the same letter are not significantly different (P = O.OS) using
Waller-Duncan's multiple range test.
_. -.,":,"
189
Table 6.4.
Effect of insecticides on populations of the
rednecked-peanutworm, Stegasta bosgueella (Chambers), larvae
in Florunner peanut, Tifton, GA., 1987-1988.
Days
Î
X no. larvae/l0 termina1s 1
Sarnpling
after
Year
date
plant i ng r
Untreated
Treated 2
Chem. check3
1987
6/30
26
O.OOa
O.OOa
O.OOa
1988
6/27
25
0.06a
O.OOa
1987
7/07
33
O.OOa
O.OOa
O.O:la
1988
7705
32
0.03a
O.OOa
o.ÛJa .
1987
7/14
40
0.06a
0.03a
0.17a
1988
7/12
39
O.OOa
O.OOa
O.03a
1987
7/21
47
0.20a
a.17a
O.50a
1988
7/18
45
0.23a
a.10a
O.03a
1987
7/28
54
O.l7a
0.17a
a.10a
1988
7/25
52
0.23a
O.l7a
0:60a
1987
8/04
61
0.17a
0.07a
0.07a
1988
8/02
59
0.03a
0.10a
0.03a
1987
8/11
68
0.03a
o.aOa
O.OOa
1988
8/08
65
1.
Means in rows and within a samp1ing date fo1lowed by
the same letter are not significantly different (P=0.05) using
Wa11er-Duncan's multiple range test on log (x+l) values.
2.
Aldicarb, 0.84 kg/ha,app1ied at p1anting and methomyl, 2.34
l/ha app1ied on 7/22, in 1987.
3.
A1dicarb, 0.84 kg/ha, applied at planting and biweek1y from
mid-June through mid-July; methomy1, 2.34 l/ha, applied week1y from
mid-July through early September; chlorpyrifos, 2.18 kg/ha, applied
in a band over-the-row at weekly interva1s from ear1y July through
late August.
190
Table 6.5.
Effect of insecticides on populations of corn
earworm, Heliothis zea (Boddie), larvae in Florunner
peanut, Tifton, GA., 1987-1988.
Days
Xno. larvae/25 sweeps1
Year
Sa~~Ung
after
plantlng
Untreated
Treated 2
Chem. check3
1987
7/14
40
0.23a
O.l7a
0.03a
1988
7/12
39
0.03a
0.07a
O.OOa
1987
7/21
47
0.50a
0.53a
0.23a
1988
7/18
45
0.53a
0.72a
0.03b
1987
7/28
54
1. 93a
1.60a
0.37b
1988
7/25
52
5.90b
9.33a
0.33c
1987
8/04
61
13.53b
25.33a
0.53b
1988
8/02
59
13.90a
13.00a
0.82b
1987
8/11
68
8.00b
18.70a
0.33c
1988
8/08
65
5.93a
7.14a
6.07a
1987
8/18
75
O.73a
0.57a
O.OOb
1988
8/18
75
0.50b
0.90a
"'
0.23b
1987
8/25
82
12.57a
13. o.:,a -'
0.33b
1988
8/29
86
14.67b
19.13a
1.60c
1987
9/01
88
22.33a
25.33a
1.86b
1988
9/07
94
1. 53a
2.00a
2.07a
1.
Means in rows and within a, samplig date followed by the
same letter are not significantly different (P=O.05) using Waller-
Duncan's multiple range test on log (x+1) values.
2.
Aldicarb, 0.84 kg/ha, applied at planting and methomyl
2.34 l/ha, applied on 7/22 in 1987.
3.
Aldicarb, 0.84 kg/ha, applied at planting and biweekly
from mid-June through mid-July; methomyl, 2.34 l/ha, applied weekly
from mid-July through early September; chlorpyrifos, 2.18 kg/ha
applied in a band over-the-row at weekly intervals from early July
through late August.
191
Table 6.6.
Effect of insecticides on populations of corn
earworm, Heliothis zea (Boddie), moths in Florunner
peanut, Tifton, GA., 1987-1988.
Days
Xno. adults/25 sweepsl
Sampling
after
Year
date
planting
Untreated
Treated 2
(hem. check3
1987
7/14
40
O.13a
0.03a
0.03a
1988
7/12
39
0.03a
O.OOa
O.OOa
1987
7/21
47
0.20a
0.23a
0.03a
1988
7/18
45
0.07a
0.28a
0.10a
1987
7/28
54
0.27a
0.23a
0.07a
1988
7/25
52
0.41a
0.10b
O.13b
1987
8/04
61
0.10a
0.23a
0.07a
1988
8/02
59
0.50a
0.28a
0.32a
1987
8/11
68
0.40a
0.20a
0.20a
1988
8/08
65
0.59a
0.52a
0.33a
1987
8/18
75
1.40a
0.97a
0.30b
1988
8/18
75
0.43a
0.97a
0.43a
1987
8/25
82
1.80ab
2.47a
0.60b
1988
8/29
86
0.40a
0.43a
0.23a
1987
9/01
88
0.43a
0.43a
0.23a
1988
9/07
94
0.33a
o.13a
0.20a
1.
Means in rows and/within a sampling date followed by the
same letter are not significantly different (P=0.05) using Waller-
Duncan's multiple range test on log (x+l) values.
2.
Aldicarb, 0.84 kg/ha, applied at planting and methomyl,
2.34 l/ha applied on 7/22 in 1987.
3.
Aldicarb, 0.84 kg/ha, applied at planting and biweekly
from mid-June through mic-July; methomyl, 2.34 l/ha, applied weekly
from mid-July through early September; chlorpyrifos, 2.18 kg/ha,
applied in a band over-the-row at weekly intervals from early July
through late August.
192
Table 6.7.
Effect of insecticides on populations of potato
leafhopper, Empoasca fabae (Harris), adults in Florunner
peanut, Tifton, GA., 1987-1988.
Days
Xno. adults /25 sweepsl
Sampling
after
Year
date
planting
Untreated
Treated 2
Chem. eheek3
1987
7/14
40
9.97a
1.73b
0.83b
1988
7/12
39
3.83a
1.27b
1.33b
1987
7/21
47
18.97a
3.93b
0.83b
1988
7/18
45
4.17a
2.00b
O. ne
1987
7/28
54
12.23a
1.57b
0.20c
1988
7/25
52
Il. 34a
4.53b
2.07e
1987
8/04
61
22.60a
0.50b
0.07e
1988
8/02
59
22.93a
5.07b
4.68b
1987
8/11
68
17.23a
6.27b
0.63e
1988
8/08
65
13.03a
6.59b
4.33e
1987
8/18
75
15.47a
10.17b
2.80e
1988
8/1B
75
21.30a
9.93b
6.03e
1987
8/2f -
82
17 .87a
13.80b
0.87e
1988
8/29
86
18.13a
5.80b
3.40e
1987
9/01
88
7.07a
5.80a
0.60b
1988
9/07
94
2.93a
1.20a
1.13b
1.
Means in rows and within a sampling date fo'llowed by the
same letter are not significantly different (P=0.05) using Waller-
Duncan's multiple range test on log (x+l) values.
-
2.
Aldiearb, 0.84 kg/ha, applied at planting .and methomyl
2.34 l/ha, applied on 7/22 in 1987.
3.
Aldicarb, 0.84 kg/ha, applied at planting and biweekly
from mid-June through mid-July; methomyl, 2.34 l/ha, applied weekly
from mid-July through early September; chlorpyrifps, 2.18 kg/ha,
applied in a band over-the-row at weekly intervals from early
July through late August.
193
lable 6.8.
Effect of insecticides on populations of lesser
cornstalk borer, Elasmopalpus lignosellus (Zeller), larvae
in Florunner peanut, lifton, GA., 1987-1988.
Days
Xno. larvae/0.5 m of row1
Sampling
after
Year
date
planting
Untreated
lreated 2
(hem. check3
1987
6/30
26
0.60a
0.23a
0.50a
1988
6/27
25
O. na
O. na
1987
7/07
33
0.03b
0.03b
0.30a
1988
7/05
32
o.10b
0.53a
0.63a
1987
7/14
40
o.10a
0.03a
0.07a
1988
7/12
39
0.20a
0.20a
0.30a
1987
7/21
47
0.03a
o.17a
0.07a
1988
7/18
45
O.l3a
0.27a
0.17a
1987
7/28
54
0.43b_
1.33a
1. na
1988
7/25
52
0.30a
o.13a
0.37a
1987
8/04
61
O.l3b
0.27ab
0.63a
1988
8/02
59
O.OOb
0.03b
0.38a
1987
8/11
68
O.30a
0.43a
O.l3a
1988
8/08
65
O.OOa
O.OOa
0.03a
1987
8/18
75
e.. 07b
0.43a
0.33ab
1988
8/18
75
t.1Ca
0.07a
0.07a
1987
8/25
82
0.07a
0.07a
O.OOa
1988
8/29
86
0.23a
o.13a
0.10a
1987
9/01
88
0.03a
O.OOa
O.OOa
1988
9/07
94
O.l7a
0.10a
0.17a
,1
!
1.
Means in rows and within a sampling date followed by the
same letter are not significantly different (P=O.OS) using Waller-
Duncan's multiple range test on log (x+l) values.
2.
Aldicarb, 0.84 kg/ha, applied at planting and methomyl,
2.34 l/ha applied on 7/22 in 1987.
3.
Aldicarb, 0.84 kg/ha, applied at planting and biweekly
from mid-June through mid-July; methomyl, 2.34 l/ha, applied weekly
from mid-July through early September; chlorpyrifos, 2.18 kg/ha,
applied in a band over-the-row at weekly inte~vals fron early July
through late August.
194
Table 6.9.
Effect of various regimes of insecticide application on
populations of adult big-eyed-bug, Gecoris spp., on Florunner
peanuts, Tifton, Ga., 1987-1988.
Days
Mean number of adults 1/25 sweeps
Sampling
Since
Year
date
Planting
Untreated
Treated 2
Chem. check3
1987
7/14
40
0.00a 4
O.OOa
O.OOa
1988
7/12
39
0.20a
0.20a
0.03a
1987
7/21
47
0.07a
0.07a
O.OOa
1988
7/18
45
0.30ab
0.45a
0.07b
1987
7/28
54
0.70a
0.40ab
O.17b
1988
7/25
52
0.79a
0.53ab
0.05b
1987
8/04
61
0.80a
0.10b
0.300
1988
8/02
59
0.43a
0.31ab
0.11b
1987
8/11
68
0.73a
0.20b
0.27b
1988
8/08
65
0.38a
0.17a
O.lOa
1987
8/18
75
1.90a
1.10b
0.43b
1988
8/18
75
2.10a
0.90b
0.37b
1987
8/25
82
1.13a
1.53a
~, 0;-,23b
1988
8/29
86
3.10a
2.93a
1.27b
1987
9/01
88
O.17a
O.17a
0.03a
1988
9/07
94
0.40a
0.60a
0.20a
1.
Geocoris spp. = ~ punctipes (Say)., ~ bullatus (Say), h
uliginosus (Say).
2.
Treatments applied: aldicarb, .84 kg/ha, at planting; also
methomyl, 2.34 l/ha applied on 7/22 in 1987 .
3.
Treatments applied: aldicarb, . 84 kg/ha, at planting and
biweekly, mid-June-mid-July; methomyl, 2.34 l/ha, weekly mid-July-early
September; Lorsban, 2.18 kg/ha in band weekly, early July-late August.
4.
Means in rows followed by the same letter are not significantly
different (P = 0.05) using Waller-Duncan's multiple range test on log
(x+l) values.
195
Table 6.10.
Effect of insecticides on populations of spiders
in Florunner peanut, Tifton, GA., 1987-1988.
Days
Xno. total spiders/25 sweeps1
Sampling
Since
Year
date
planting
Untreated
Treated 2
Chem. check3
1987
7/14
40
l.13a
0.50ab
O.23b
1988
7/12
39
1.23a
0.73a
1.07a
1987
7/21
47
2.70a
1.00b
1.26c
1988
7/18
45
1.40a
0.96ab
0.70b
1987
7/28
54
2.53a
0.83b
0.63b
1988
7/25
52
1.96a
1.OOb
0.43c
1987
8/04
61
2.73a
0.43b
O.93b
1988
8/02
59
0.80a
1. 41a
1.36a
1987
8/11
68
1.60a
1.23a
0.70b
1988
8/08
65
2.86a
2.90a
1.40b
1987
8/18
75
3.37a
1. 53b
0.37c
1988
8/18
75
4.67a
2.63b
1.67b
1987
8/25
82
3.13a
1.47b
0.67b
1988
8/29
86 ..
4.63a
2.90b
1.27c
1987
9/01
88
1.87a
0.67b
0.23b
1988
9/07
94
3.47a
3.27a
O.87b
1
The term "spiders" is used as a generic entity and includes
severa1 species and stages.
Means in rows and within a sampling dat~
follow~d by the same letter are not significantly different (P=0.05)
using'~aller-Duncan's multiple range test on log (x+1) values.
2.
Aldicarb, 0.84 kg/ha, applied at planting methomyl, 2.34 l/ha
applied on 7/22 in 1987.
·3.
Aldicarb, 0.84 kg/ha, applied at planting and biweekly
From mid-June through mid-July; methomyl, 2.34 l/ha, applied weekly
frommid-July through early September; chlorpyrifos, 2.18 kg/ha,
appiied in a band over-the-row at weekly intervals From early July
through late August.
196
Table 6.11.
Effect of insecticides on total predator populations
in Florunner peanut, Tifton, GA., 1987-1988.
Days
X no. total predators/25 sweeps1
Sampling
Since
Year
date
planting
Untreated
Treated 2
Chem. check3
1987
7/14
40
1.50a
0.73b
0.30b
1988
7/12
39
2.57a
1. 93a
1.43a
1987
7/21
47
3.57a
1.60b
1.53b
1988
7/18
45
2.l3a
1. 76a
O.87b
1987
7/28
54
4.77a
1.80b
O.93b
1988
7/25
52
2.93a
1.63b
0.50c
1987
8/04
61
4.17a
1.07b
1.37b
1988
8/02
59
1.33a
1.79a
1.50a
1987
8/11
68
3.00a
2.37a
1.l3b
1988
8/08
65
4.48a
3.96a
2.80b
1987
8/18
75
8.20a
4.27b
1.27c
1988
8/18
75
8.60a
5.43b
2.53b
1987
8/25
82
6.10a
4.10b
1.00c
>1"-
_
-...
~' ••
- -
.'&:
....
1988
8/29
86
9.33a
6·; 80b
2.77b
-'.
1987
9/01
88
2.57a
1.30b
0.87c
1988
9/07
34
4.87a
4.53a
1.40b
1.
Total predators include (Spiders, flower bugs, big-eyed
bugs, Nabids, Lady beetles, and Staphylinid beetles).
Means in
rows and within a sampling date followed by the same letter are
not significantly different (P=~~05) using Waller-Duncan's
multiple range test on log (x+1) values.
2.
Aldicarb, 0.84 kg/ha, applied at planting and methomyl,
2.34 l/ha applied on 7/22 in 1987.
3.
Aldicarb, 0.84 kg/ha, applied at planting and biweekly
from mid-June through mid-July; methomyl, 2.34 l/ha, applied weekly
from mid-July through early S~ptember; chlorpyrifos, 2.18 kg/ha,
applied in a band over-the-row at weekly intervals from early July
through late August.
197
Table 6.12.
Effect of insecticides on populations of parasitic
Hymenoptera in Florunner peanut, Tifton, GA., 1987-1988.
Days
Xno. adult parasitoids/25 sweeps1
Sampling
Since
Year
date
planting
Untreated
Treated 2
Chem. check3
1987
7/14
40
0.03a
o.10a
0.03a
1988
7/12
39
O.13a
0.07a
O.13a
1987
7/21
47
0.37a
o.13a
0.03a
1988
7/18
45
0.60a
0.31a
0.03a
1987
7/28
54
O.13a
0.10a
0.03a
1988
7/25
52
o.14a
0.13a
O.OOa
1987
8/04
61
O.OOa
o.10a
0.07a
1988
8/02
59
O.13a
0.07a
0.04a
1987
8/11
58
0.30a
0.40a
0.10a
1988
8/08
65
0.34a
0.83a
0.53a
1987
8/18
75
0.57a
0.60a
0.20a
1988
8/18
75
2.97a
3.53a
l.13a
1987
8/25
82
0.20b
0.60a
0.03b
1988
8/29
86
13.10a
11.80a
2.03b
1987
9/01
88
0.17a
o.10a
0.03a
1988
9/07
34
0.93a
1.20a
0.67a
1.
Parasite species include:
Microplitis croceipes (Cresson),
Cardiochiles nigriceps Viereck, Pristomerus spinator (F.), Netelia
heroica Townes, and Meteorus sp ..
Means in rows and wHhin
a sampling date followed by the same letter are not sig~ificantly
different (P=O.üS) using Waller-Duncan's multiple rang~ test on
log (x+1) values.
2.
Aldicarb, 0.84 kg/ha, applied at planting and· methomyl, 2.34
l/ha applied on 7/22 in 1987.
3.
Aldicarb, 0.84 kg/ha, applied at planting and biweekly
from mid-June through mid-July; methomyl, 2.34 l/ha, applied weekly
from mid-July through early September; chlorpyrifos, 2.18 kg/ha,
applied in a band over-the-row at weekly intervals from early July
through late August.
Table 6-13.
Influence of insecticides on plant density and reproductive structures for Florunner peanut,
Tiftari, GA, 1987-19~8.
!
li
Average number 10.Sm of row1
•!
Days
Plants
Flowers
Pegs
Pods
Sampling
sinee
,J}... 2
TR 3
CC 4
Year
date
planUng
• . 1
UT
TR
CC
UT
TR
CC
UT
TR
CC
1987
6/30
26
6.5a
6.2a
5.9b
1988
6/27
25
7.4a
6.5a
1987
7/07
33
5.1a
5.5a
6.2b
1988
7/05
32
7.7a
6.9a
8.0a
1987
7/14
40
4.Sa
4.3a
4.7a
20.1a
19.2a
13.2a
1988
7/12
39
7.0a
6.6a
7.1a
13.0a
11.Sa
7.1a
1987
7/21
47
S.3a
4.5b
4.5b:
---
1988
7/18
45
6.Sa
6.9a
6.4a
39.7b
45.0a
43.4a
35.1b
37·.8a
31.3c
1987
7/28
54
5.3a
5.4a
4.6b
60.3a
60.1a
46.2a
31.5b
53.2a
18.3c
1988
7/2S
52
6.2a
6.0a
6.3a
53.la
61. 3a
60.4a
50.5b
90.7a
54. oc
1987
8/04
61
2.3a
2.4a
2.3a
71.4b
90.4a
89.6a
65.6a
48.1b
70.8a
1988
8/02
59
5.7a
5.7a
5.3a
39.6a
36.8a
43.3a
150.4a
174.3b
130.4c
.
1987
8/11
68
3.4a
3.3a
3.3a
---
58.6a
22.3e
S3.51b
2i.7a
22.3b
22.7b
1988
8/08
65
5.3a
5.0a
5.5a
144.2b
132.8b
163.3a
42.8a
42.4a
28.9b
1987
8/18
75
2.4a
2.Sa
2.3a
---
2S0.8a
193.9b
204.1b
37.2a
42.1a
2i.6b
1988
8/18
75
4.8a
5.0a
S.7a
176.6c
207.2b
243.6a
66.8a
50.7b
64.8a
1987
8/25
82
2.5a
2.8a
2.9a
---
111. 8b
102.7b
287.2a
47.5b
41.3b
89.3a
1988
8/29
86
5.2a
4.6a
5.5a
94.4c
144.6b
179.0a
93.Sa
83.1a
89.6a
......
<.0
CD
Table 6-1~ (continued)
..
Average n~mber 10.5m of row.
Days
Pl ants
Flowers
Pegs
Pods
Sampling
since
Year
date
planting
UT
TR
CC
.lJT
·TR
CC
UT
TR
CC
IH
TR
CC
1987
9/01
88
3.7a
3.0b
2.8b
---
156.8a
153.3a
266.7b
159.0a
113.1b
155.6a
1988
9/07
94
5.4ab 4.5a
5.9b
101.4a
153.9b
160.0c
107.6a
86.6b
99.8a
1. M~ans in rows followed by the same letter are not significantly different (P • 0.05) using Waller-Duncan's
multiple range test.
2.
UT - Untreated plots.
•
3.
Ald icarb, 0.84 kg/ha, applied at planting methomyl, 2.34 l/ha applied on 7/22 in 1987 .
t.,
~
4.
Aldi~arb, 0.84 kg/ha, .applied at planting and biwe~kly from mi~-June through mid-July;methomyl, 2.34 I/ha,
J
~applled weekly fro~.mld-July through early September; chlorpyrlfos. 2.18 kg/ha applied in a band over-the-
row at weeklv i~~rvals from early July through late August.
1 - '
<0
<0
200
Table 6.14.
Influence of Insecticides on fresh welghl of florunner
peanul planls and pods, llflon, Ga., 1987-88.
1 fresh weighl /0 5m of row l
Slems and leaves
Pods
Days
Sampllng
since
Year
dale
planling
Unlrealed
lrealed2
Check3
Unlrealed
lrealed
Check
1987
6/30
26
9.18a
8.19lJ
7.38c
1988
6/21
25
10.82a
11.61a
1987
7/01
33
9.18a
8.Ha
7.41b
1988
7/05
32
23.41b
28.28a
22.24b
1987
7/14
40
34.95c
41.19b
55.60a
1988
1/12
39
42.24b
41.46a
3B.31b
19B7
7/21
41
59.73b
48.92b
82.55a
198B
7/18
45
83.44b
J04.D2a
67.62c
1981
7/28
54
112.66a
189.3Ca
Ill.39b
1988
7/25
52
128.30ab
144.02a
JJ6.10b
1981
8/04
61
267.85a
251.47ab
189.31b
1988
8/02
59
151.37b
198.84a
140.33b
1981
8/1l
68
219.Ila
251.B4a
254.04a
11.00a
10.51a
9.02a
1988
8/0B
65
161.51ab
113.35a
153.20b
16.78a
16.45a
10.llb
1981
B/IB
15
262.6Ba
192.64a
341.82a
8.06b
6.34b
12.11a
1988
8/18
15
206.12a
·20a.'50a
188.49a
32.90a
26.13ab 25.00b
1981
8/25
82
212.16b
28).26b
489.32a
44.66a
38.0Ia
31.06a
1988
8/29
86
200.24a
246.83a
218.25a
51.30a
48.80a
44.20a
1981
9/01
88
3BB.B9a
454.54a
485.13a
62.Ila
51.28a
11.54a
1988
9/01
94
196.48a
222.57a
197.43a
62.43a
56.01a
56.36a
.i
1.
Means in rows and wilhin a sampling da le are nol significanlly differenl
,
(P • 0.05) using Waller-Ouncan's mulliple range lesl.
1
2.
Aldicarb, 0.84 kg/ha, applied al planting and melhomyl. 2.34 I/ha applied on
1/22/81. •
3.
Aldicarb, 0.84 kg/ha, applied al planling and biweekly from mid-June lhrough
mid-July; rnethomyl, 2.34 I/ha, appl ied weekly from mid-July lhrough mid-Seplermberj
chlorpyrffos, 2.18 kg/ha applied III a band over-lhe-row al weekly inlervals from
July lo lale Augusl.
201
Tahle 6.15.
Influence of Insecticldes on dry weighl of rlorunner peanlll planls,
and pods, Tiflon, Ga.,1987-88.
Xdry weighl /0 Sm of row1
Slems ancr1eaves
Pods
f)ays
Sampling
sinee
Trealed 2
Check3
Vear
dale
planting
Unlrealed
Unlrealed
Trealed
Check
1987
6/30
26
0.69a
0.58h
0.69a
1988
6/27
25
1.24a
1.06b
1987
7/07
33
2.56a
2.01h
1.81h
1988
7/05
32
5.69a
4.59b
3.94e
1987
7/14
40
4.93b
7.47a
4.70b
1988
7/12
39
4.95a
4.53a
4.83a
lM7
7/21
47
6.88a
4.60b
6.04ab
1988
7/18
45
9.54b
15.34a
8.33b
1~87
7/28
54
15.03h
19.48a
Il. 72e
1988
7/25
52
19.38a
21.49a
17 .07b
. H87
8/04
61
1988
8/02
59
24.92b
31.04a
22.83b
..1987 8/11
68
26.58a
25.35a
26.40a
3.02a
3.lIa
2.80a
1988
8/08
65
28.32ab
29.46a
25.71b
<
3.08a
2.90a
1.47a
1987
8/18
75
24.29a
28.92a
32.94a
3.22b
2.63b
4.24a
1988
8/18
75
32.28a
34.37a
30.69a
5.54a
S.10a
3.90a
1987
8/25
82
35.74b
50.40b
88.01a
9.36a
7.98a
8.16a
1988
8/29
86
35.36a
42.40a
37.68a
12.24ab
13.41a
9.69b
1987
9/01
88
67.12a
77 .12a
76.52a
17.00a
18.95it
21.IIa
1988
9/07
94
34.30a
39.0la
34.40a
20.24a
19.75a
14.63b
!
1.
Heans in rows and wilhin a sampling dale are nol signlflcanlly differenl
(P e 0.05) using Waller-Ounean's multiple range tesl.
2.
Aldicarb, 0.84 kg/ha applied at ~lanling andmethomyl, 2.34 I/ha applied on
7/22/87.
3.
Aldicarh, 0.84 kg/ha, applied al planling and biweekly from mid-June through
mid-July; methomyl, 2.34 I/ha, appl ied wp.ekly from mid-July throtlgh mid-Septermber;
chlorpyriros, 2.18 kg/ha applied in a band over-lhe-row al weekly inlervals from
JlIly lo lale August.
202
Table 6.16.
Influence of insecticides on yield of Florunner
peanut, Tifton Ga., 1987-1988.
Yield (kg/ha)
Rate
Treatment
(per ha)
1987
1988
Untreated
4312.3a l
4388.07a
Treated
Aldicarb
o.84kg
4254.1a
4355.91a
Chemical check
Aldicarb
0.84kg
Chlorpyrifos
2.18kg
Lannate
.- 2.341
4160.4a
3753.68b
1.
Means in columns followed by the same letter are not
significantly different (P = 0.05) using Waller-Duncan's multiple range
test.
.f
/
203
Table 6.17.
Pearson correlation coefficients for selected
insect pest species versus dry weight of above ground vegetative
structures and pods of Florunner peanuts.
Dependent variable
Sampling
Insect pests
method
Dry top weight
Dry pod weight
Thrips (immatures
10 term-inals
-0.1671
-0.1114
Rednecked
peanutworm
10 terminals
+0.1144
+0.1156
Corn earworm
25 sweeps
-0.0885
-0.0168
Lesser cornstalk
borer
1/2m row
-0.1210
-0.0960
_1
/
204
LITERATURE CITED
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1989.
Ecology of spiders (Araneae)
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Insecticide and Acaricide 4:143
Berberet, R. C. and F. Guilavogui.
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Control of red-necked
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Insecticide and'Acaricide
!
Test 5:141
Bradley, J. R., Jr., M. L. Laster, H. N. Pitre, S. H. Roach, and J. W.
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1987.
Interactions of insecticides and arthropod natural
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Southern Coop. Series Bull. No. 329.
205
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Croft, B. A., and A. W. A. Brown.
1975.
Responses of arthropod
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Ann. Rev. Entomol. 20:285-335.
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1980.
Response of Labidura riparia to
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Amer. Peanut Res. Educ. Assoc. 12:50 (Abstract)
Elsey, D. K. and J. S. Cheatum.
1976.
Conta:t toxicity of
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Tobacco Sei. 20:81-88.
Farlow, R. A. and H. N. Pitre.
1983.
Effects of selected pesticide
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French, J. C."
1973.
Insect pest management on peanuts in Georgia.
APREA 5:125-127.
i
.'
Green, G. L., W. H. Whitcomb and R. Baker.
1974.
Minimum rates of
/
. "
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1966.
Natural cross-pollination of
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Agron. J. 58:396.
206
Harding, J. A.
1960.
Control of lesser cornstalk borer attacking
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J. Econ. Entomol. 53:664-667.
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PP 29-30.
ln
Theory And Tactics Of Heliothis Population Management
II.
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Kennedy, G. G., J. R. Young and R. B. Chalfant.
1987.
Efficacy of
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1979.
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Mississipi.
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Effects of
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207
Luck, R. F., R. V. den Bosch and R. Garcia.
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Chemical insect
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Influence of
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Susceptibility of a migratory population
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Populations of corn earworm-and 'associated predators after
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!
Plapp, F. W. Jr., and D. L. Bull.
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Toxicity and selectivity of
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Ridgway, R. L. , P. D. Lingren, C. B. Cowan, Jr.
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Populations of arthropod predators and
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Thrips control in peanuts.
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Response of bollworm and
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Tappan, W. B.
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Tobacco thrips (Thysanoptera: Thripidae) number
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79:1082-1084.
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Relationship of seasonal
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J. fcon. Entomol. 72:772-776.
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Economie of tobacco thrips
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J. fcon. Entomol. 74:283-286.
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Effect of irrigation and
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Ecology of the true spiders (Araneomorphae).
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Field activity
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spiders on soybeans.
J. Ga. Entomol. Soc. 10: 272-277 .
.i
WalJ, R. G. and R. C. Berberet.
1979.
Reduction in leaf area of
.'1"
spanish peanuts by rednecked peanutworm. J. Econ. Entomol. 72:671-
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Waller, R. A., and D. B. Duncan.
1969.
A Bayes rule for the symetrie
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J. Amer. Stat. Assoc. 64:1684-1699.
210
Walton, R. R. and R. Matlock.
1959.
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Wolfenbarger, O. A., S. M. Mayeux, R. J. Palazzo, J. B. Graves, J.
R. Raulston and L. Guerra-Sobreville.
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Bollworm and tobacco
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J.
Agric. Entomol. 4:141-152.
,1
/
VII. GENERAL CONCLUSIONS
Results from investigations on the comparative efficiencies of
several methods for sampling pest and beneficial arthropods on pean ut
and the influence of plant phenology, irrigation, and insecticide
applications on the seasonal abundance of these arthropods lead to the
following conclusions:
1.
Population estimating efficiency of the four sampling
procedures varied with developmental stage and feeding
behavior of a particular insect species.
Thus, insect pest
species-~eeding primarily within the folded leaves of pean ut
terminals, i. e., thrips, early larval stages of H. zea, and
virtually all larvae of ~. bosgueella, were more efficiently
sampled by terminal examination than by other methods.
Con~ersely, sweep net samples yielded higher population
estlmates of mobile adults of pest and predaceous insects.
Consequently, no one sampling method alone may be suitable for
estimating populations of all stages and species of arthropods
found in peanut.
2.
Considered singly, all sampling methods w~e self-limiting
since their efficiencies are relative.
However, a combination
of terminal examination and sweep net sampling could yield
valuable information on the seasonal trends for most arthropod
211
212
populations on peanut.
Data from a combination of these
sampling methods converted to a more quantitative form will
provide more reliable population estimates than beat and shake
method currently used to sample peanut arthropods.
3.
Tobacco thrips, E. fusca, were the most abundant
arthropod species collected from peanut fields in 1986, 1987,
and 1988.
Generally, adults accounted for a greater portion
of the thrips populations in flowers than in terminals.
Thrips
populations in both terminals and flowers were highest during
early season, and declined as the season progressed.
4.
Throughout the 3-year study, larval populations of the corn
earworm, H. zea, and red-necked peanutworm, ~. bosqueella, were
extremely low early in the season, increased as the season
progressed, and reached maximun densities in mid- to late July
to early to mid-August.
The proposed threshold levels of ca.
4 larvaejO.30 m of row were not reached in any of the three
years.
Thus, the se pests are only occasional pests of peanut
and their control by insecticidal applications may not be
necessary for most years in south Georgia.
5.
Population~ of the lesser cornstalk borer, f. lignosellus,
followed e~sentially the same trends in 1986, 1987, and 1988.
Larval populations slowly increased from low densities during
the first'weeks of sampling to reach peak populations from
mid-July to mid-August.
The greatest population build up of
f. lignosellus coincided with peanut growth stages susceptible
to damage by this pest, i.e., beginning peg to full seed
stages.
Populations of lesser cornstalk borer were much higher
213
in 1986 than either 1987 or 1988, probably as a result
of the drought which occurred in 1986.
6.
Peak populations of predators coincided with peak densities of
pest species from late July to August.
Although most predator
species, including Geocoris spp., nabids, and spiders, may be
facultatively phytophagous and cannibalistic, their population
levels paralleled population changes of their potential prey.
7.
Timely applications of irrigation in 1986 reduced populations
of thrips and red-necked peanutworm in terminals, while
encouraging populations of potato leafhopper to increase.
Irrigation had little effect on populations of corn earworm
1~rvae.
Reductions in E. fusca and ~. bosqueella populations
were probably a consequence of faster growth for plants in
irrigated plots than for plants in nonirrigated plots.
This
increased growth rate resulted in more rapid leaf growth and
expansion, thus providing a shorter time period over which
-terminals were produced on plants in irrigated plots and a
shorter period for thrips to feed in individual terminals.
Conversely, the enhancement of more vigorous and succulent
vegetative growth on irrigated plants may have promoted greater
leafhopper populations on plants in(irrigated plots.
8.
Irrigation also markedly reduced populations of lesser
cornstalk borer larvae.
However, iittle effect of irrigation
on I. lignosellus adult populations was noted, probably due to
adult movement among plots.
During the period of highest
population densities, mid-July ta mid-August, the number of
2]4
larvae/m of row in nonirrigated plots was almost three times
higher than the number in irrigated plots.
9.
Of all arthropods predators collected in 1986, spiders were
most were most affected by irrigation.
The number of spiders
was significantly higher in irrigated than in nonirrigated
peanut in 5 of 8 weekly samples.
This difference was possibly
due to a better canopy development in irrigated plots, which
created more climatically suitable niches for colonization by
various spider species.
la.
Overall, studies on the impact of irrigation on populations of
peanut arthropod complex indicate that when appropriately applied,
irrigation can reduce infestation levels of several pest species,
including thrips, red-necked peanutworm, and lesser cornstalk
borer while increasing populations of spiders.
Il.
Infestation and damage levels for several peanut p~st species
-
were significantly reduced by application of insecticides.
Pest
species successfully controlled by applications oraluïcarb
and/or aldicarb plus methomyl and chlorpyrifos included tobacco
thrips, potato leafhopper, and corn earworm.
In contrast, these
insecticides had little or no noticeable "impact on populations
of red-necked peanutworm and lesser cornstalk borer larvae.
12.
Application of aldicarb at planting promoted greater leaf mass
production by treated plants, which probably enhanced the
attractiveness of these plants to ovipositing tl. zea and, thus,
accounted for the observed greater number of corn earworm larvae
in aldicarb-treated plots as compared to larvae in untreated
plots.
2]5
13.
All insecticides reduced numbers of Geocoris spp., nabids, and
spiders, but significant reductions in numbers of these
predators occurred only after application of methomyl.
However,
none of the insecticides applied had any effect on populations of
parasitoids.
14.
Although insecticide applications reduced infestation and damage
levels by several pest species, peanut yields in 1987 and 1988
were not significantly increased as a result of chemical
treatments.
Thus, it appears that, under the insect pressures
encountered in this study, insecticide applications may not be
necessary in many years to obtain maximun peanut yield in south
Georgia.
These results also indicate the importanc~ of sampling
to monitor populations of pest and beneficial arthropods in
peanut.
Their implementation in a pest management ~ystem for
pean ut would probably reduce the amount of inse~tieide applied
to peanut.
215
13.
All insecticides reduced numbers of Geocoris spp., nabids, and
spiders, but significant reductions in numbers of these
predators occurred only after application of methomyl.
However,
none of the insecticides applied had any effect on populations of
parasitoids.
14.
Although insecticide applications reduced infestation and damage
levels by several pest species, peanut yields in 1987 and 1988
were not significantly increased as a result of chemical
treatments.
Thus, it appears that, under the insect pressures
encountered in this study, insecticide applications may not be
necessary in many years to obtain maximun peanut yield in south
Georgia.
These results also indicate the importance of sampling
to monitor populations of pest and beneficial arthropods in
peanut.
Their implementation in a pest management system for
peanut would probably reduce the amount of insecticide applied
to peanut.
,1
1
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i ' l'
j
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! '
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•1
!
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APPENùIX
.i
!,
236
237
Table 3-2.
Relative frequencies for arthropods collected in peanut
by four sampling methods, Tifton, Ga., 1986.
Sampling
Sample
Relative
method
unit
Anthropod species/group
frequency (%)
Flower
la flowers
Thysanoptera: Thripidae
Frankliniella fusca (Hinds)
immatures
52.19
adults
43.17
Prostigmata: Tetranychidae
Tetranychus urticae Koch
1.19
Lepidoptera: Gelechiidae
Stegasta bosguella (Chamb.)
larvae
0.86
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
1arvae
Lepidoptera: Pyralidae
Elasmopalpus lignosellus (Zeller)
larvae
0.12
Homoptera: Cicadellidae
nymphs
0.57
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
0.59
adults
0.34
Diptera
0.10
Terminal
la terminals
Thysanoptera: ~hripidae
Frankliniellr fusca (Hinds)
immatures '
66.57
adult
18.37
Lepidoptera: Gelechiidae
Stegasta bosquella (Chamb.)
larvae
6.05
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
larvae
4.29
_~'
_ ,
T'
. " .
23E~
Table 3.2. (cont'd)
Sampling
Sample
Relative
method
unit
Arthropod species/group
frequency (%)
Hemiptera: Anthocoridae
Orius insidiosus (Says)
nymphs
1.84
adults
1. 79
Homoptera: Cicadellidae
nymphs
1.10
Whole Plant
No plants/0/5m
of row
Thysanoptera: Thripidae
Frankliniella fusca (Hinds)
immatures
63.31
adults
17.83
Homoptera: Cicadellidae
nymphs
7.31
fmpogasca labae (Harris)
adults
0.51
Lepidoptera: Gelechiidae
Stegasta bosquella (Chamb.)
larvae
4.07
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
larvae
1.12
Spodoptera frugiperda (J.f. Smith)
larvae
0.24
.1
1
Feltia subterranea (F)
larvae
0.003
Lepidoptera: Pyralidae
flasmopolpus lignosellus (Zeller)
larvae
1.00
Araneida
1.43
Prostigmata: Tetranychidae
Tetranychus urticae Kach
0.62
239
Table 3.2 (cont'd)
Sampling
Sample
Relative
method
unit
Arthropod species/group
frequency (%)
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
0.97
adults
0.35
Hemiptera: Lygaeidae
Geocoris spp.
nymphs
0.02
adults
0.00
Coleoptera: Staphylinidae
Sepedophilus sp.
larvae
0.34
adults
0.14
Coleoptera: Elateridae
Conoderus spp.
larvae
0.11
adults
0.00
Coleoptera: Coccinellidae
l arvae
0.00
Hippodamia converge~s
adults
0.03
Oiptora
0.10
Sweep net
10 sweëps
Homoptera: Cicadellidae
Empoasca labae (Harris)
adults
46.29
Cuerna costalis (Fabr.)
Scaphytopius frontabis (Van Ouzeo)
Aceratagallia sanguinolenta (Prov.) -
Oraeculacephala balli (Van Ouzeo)
Homoptera: Fulgoroidea
4.34
Oiptera
18.26
Araneida
6.80
__
~
.,J"
....~ ,-
- .
240
Table 3.2 (cont'd)
Sampling
Sample
Relative
method
unit
Arthropod species/group
frequency (%)
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
larvae
4.85
adults
0.86
Spodoptera frugiperda (J.E. Smith)
larvae
0.22
adults
1.43
Feltia subterranea (F)
larvae
0.16
adults
0.05
Lepidoptera: Pyrolidae
Elasmopalpus lignosellus (Zeller)
larvae
0.66
adults
2.32
Lepidoptera: Gelechiidae
Stegasta bosquella (Chamb.)
larvae
0.39
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
0.00
adults
3.38
Hemiptera: Lygaeidae
Geocoris spp.
nymphs
0.04
adults
0.98
Hemiptera: Nabidae
,i
adults
0.54
1
Hemiptera: Pentatomidae'
Podisus maculiventris (Say)
adults
0.33
Coleoptera: Coccinellidae
larvae
0.001
Hippodamia convergens (G.
Meneville)
adults
0.34
241
Table 3.2. (cont'd)
Sampling
Sample
Relative
method
unit
Arthropod species/group
frequency (%)
Coleomeqilla maculata Lengi.
Timberlake
adults
0.001
Coleoptera: Carabidae
Lebia viridipennis Dejean
adults
1.30
Coleoptera: Staphylinidae
Sepedophilus sp.
l arvae
0.06
Coleoptera: Chrysomelidae
Alticinae
adults
1. 50
Orthoptera: Tettigonidae +
Acrididae
3.75
Hymenoptera Ichneumonidae +
Braconidae
0.03
Neuroptera: Chrysopidae
Chrvsopa sp.
larvae
0.10
.f
!
•
' _ . _ : ,
-.:iIIo<.~..:ol:: ....
242
Table 3-3.
Relative frequencies for arlhropods collecled in peanul
by four sampling methods, Tiflon, Ga., 1987.
Sampling
Sample
Relative
method
unit
Arthropod species/group
frequency (%)
Flower
10 flowers
Thysanoptera: Thripidae
Frankliniella fusca (Hinds)
immatures
43.64
adults
54.10
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
larvae
0.97
Lepidoptera: Gelechiidae
Stegasta bosguella (Chamb)
larvae
0.28
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
0.15
Homoptera: Cicadellidae
nymphs
0.44
Prostigmata: Tetranychidae
Tetranvchus urticae Koch.
0.17
Araneida
0.11
Hymenoptera: Ichneumanidae
+
Braconidae
0.09
Terminal
la terminals
Thysanoptera: Thripidae
Franklini·ella fusca (Hinds)
immatures
76.41
adult
19.64
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
1.45
Lepidoptera: Pyralidae
Elasmopalpus lignosellus (Zeller)
larvae
0.08
243
Table 3.3. (cont'd)
Sampling
Sample
Relative
method
unit
Arthropod species/group
frequency (~~)
Lepidoptera: Gelechiidae
larvae
0.78
Prostigmata: Tetranychidae
Tetranychus urticae Koch
0.65
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
0.46
adults
0.11
Araneida
0.13
Whole Plant
No plants/O. SOm
row
Thysanoptera: Thripidae
Frankliniella fusca (Hinds)
immatures
58.02
adults
18.41
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
larvae
10.54
adults
0.01
Lepidoptera: Pyralidae
Elasmopalpus lignosellus (Zeller)
larvae
2.77
Lepidoptera: Gelechiidae
larvae
3.02
Homoptera: Cicadellidae
nymphs
./
3.51
Empogasca labae (Harris)
adults
/,
0.28
Coleoptera: Staphylinidae
Sepedophilus sp.
immatures
0.33
adults
0.66
Coleoptera: Coccinellidae
immatures
0.11
adults
0.14
244
Table 3.3. (cont'd)
Sampling
Sample
Relative
method
unit
Arthropod species/group
frequency (%)
Coleoptera: Elateridae
Consderus spp.
larvae
0.53
adults
0.09
Coleoptera: Carabidae
0.21
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
0.48
adults
0.01
Hemiptera: Lygaeidae
adults
0.05
Prostigmata: Tetranychidae
Tetranychus urtit~e Koch
0.19
Hymenoptera: Ichneumonidae
+
Braconidae
0.04
Araneida
0.58
Sweep net
25 sweeps
Homoptera: Cicadellidae
Empoasca labae JHarris)
adults
34.32
Lepidoptera: Noctuidae
larvae
23.57
adults
3.08
Spodoptera frugiperda (J.E. Smith)
.1
l arvae
0.01
1
.
Lepidoptera: pyralidae
Elasmopalpus lignosellus (Zeller)
l arvae
0.02
adults
3.59
Lepidoptera: Gelechiidae
Stegasta bosquella (Chamb.)
larvae
0.33
245
Table 3.3. (cont'd)
Sampling
Sampl e
Relative
method
unit
Arthropod species/group
frequency (%)
Orthoptera: Tettigonidae
+
Acrididae
6.23
Homoptera: Fulgoroidae
nymphs
0.10
adults
3.54
Hemiptera: Lygaeidae
Geocoris spp.
nymphs
0.14
adults
3.16
Hemiptera: Anthocoridae
Orius insidiosus (Say)
adults
1. 33 - -
Hemiptera: Nabidae
adults
2.62
Hemiptera: Pentatomidae
Podisusmaculiventris (Say)
nymphs
0.30
adults
}:03
Hymenoptera: Ichneumonidae
+
Braconidae
1. 75
Dermaptera: Forficulidae
Doru taeniatum (Dohrn)
nymphs
0.53
adults
1. 01
Coleoptera: Staphylinidae
larvae
0.19
adults
0.32
Coleoptera: Chrysomelidae
Alticinae
adults
0.29
24G
Table 3.3. (cont'd)
Sampling
Sample
Relative
method
unit
Arthropod species/group
frequency (%)
Coleoptera: Coccinellidae
Hippodamia convergens (G.
Meneville)
adults
0.20
.1
1
.
.
. ...... .......
~,
-
247
Table 3-4.
Relat ive frequencies for arthrapods collected in peanut
by four sampling methads, lifton, Ga., ]988.
Sampling
Sample
Relative
method
unit
Arthropad species/group
frequency (%)
Flower
]0 fl OIvers
Ihysanoptera: Thripidae
Frankliniella fusca (Hinds)
immatures
51.16
adults
45.60
Lepidoptera: Nactuidae
Heliothis zea (Boddie)
larvae
1. 63
Lepidoptera: Gelechiidae
Stegasta bosquella (Chamb.)
l arvae
0.27
Prostigmata: Tetranychidae
letranvchus urticae Koch
0.43
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
0.62
adults
0.05
-
Homsptera: Cicadellidae
nymphs
0.22
Termina l
10 termina"·s
Thysanoptera: Thripidae
Frankliniella fusca (Hinds)
immatures
76.18
adult
18.21
Lepidoptera: Noctuidae
Heliothis zea (Boddie)
l arvae
3.82
.1
Lepidoptera: Gelechiidae
1
Stegasta bosquella (Chamb.)
larvae
0.75
Lepidoptera: Pyralidae
Elasmopalpus lignosellus (Zeller)
larvae
0.03
248
Table 3.4. (cont/d)
Sarnpling
Sample
Relative
rnethod
unit
Arthropod species/group
frequency (%)
Herniptera: Lygaeidae
Geocoris spp
adults
0.65
Hemiptera: Anthocoridae
Orius insidiosus (Say)
adults
0.31
Prostigmata: Tetranychidae
Tetranvchus urticae Koch
0.34
Homoptera: Cicadellidae
nymphs
0.23
Whole Plant
No plants/0.50m
row
Thysanoptera: Thripidae·
Frankliniella fusca (Hinds)
immatures
47. II
adults
23.83
Lepidoptera: Noctuidae
Heliothis zea (Boddi~)
larvae
9.30
Lepidoptera: Gelechiid~e
Stegasta bosquella (Ehamb.)
larvae
8.16
Lepidoptera: Pyralidae
Elasmopalpus lignosellus (Zeller)
larvae
2.92
Homoptera: Cicadellidae
nymphs
0.01
Empogasca labae (Harris)
adults
4.50
Coleoptera: Staphylinidae
Sepedophilus sp.
larvae
1.09
adults
0.39
249
Table 3.4. (cont'd)
Sampling
Sample
Relative
method
unit
Arthropod species/group
frequency (%)
Coleoptera: Elateridae
Conoderus spp.
larvae
0.92
Coleoptera: Coccinellidae
larvae
0.05
Araneida
0.36
Hemiptera: Lygaeidae
nymphs
0.24
adults
0.05
Hemiptera: Anthocoridae
nymphs
0.07
adults
0.07
Hymenoptera: Ichneumonidae
+
Braconidae
0.02 .
Sweep net
25 sweeps
Homoptera: Cicadellidae
Empoasca labae (Harris)
adults
36.47
Lepidoptera: Noctuidae
Heliothiszea (Boddie)
larvae
18.32
adults
2.28
Loopers
0.82
Spodoptera frugiperda (J.E. Smith)
larvae
0.02
Lepidoptera: Gelechiidae
Stegasta bosgueella (Chamb.)
larvae
0.69
Lepidoptera: Pyralidae
Elasmopalpus lignosellus (Zeller)
larvae
0.01
adults
4.77
250
Table 3.4. (cont'd)
Sampling
Sample
Relative
method
unit
Arthropod species/group
frequency (%)
Araneida
13 .84
Hymenoptera: Ichneumonidae
+
Braconidae
6.11
Hemiptera: Lygaeidae
Geocoris supp.
nymphs
0.21
adults
3.61
Hemiptera: Anthocoridae
Orius insidiosus (Say)
nymphs
0.01
adults
2.44
- -
Hemiptera: Nàbidae
4.57
Hemiptera: Pentatomidae
Podisus maculiventris (Say)
nymphs _
0.46
aduTis-·
0.49
Coleoptpfa:"Coccinellidae
la,Fyar .
0.19
Coleol~gjlla maculata Lengi-Timberlake
adults
0.44
Hippodam~a convergens (G-Meneville)
adults
0.08
Coleoptera: Staphylinidae
Sepedophilus sp.
l arvae
0.06
.1
adults
0.08
/
Dermaptera: Forficulidae
nymphs
0.02
adults
0.15