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Relative Effectiveness of Insecticide Sprays on Insect Damage and Yield of Three Cowpea Cultivars in Swaziland

Published online by Cambridge University Press:  19 September 2011

G. W. K. Mensah
G. W. K. Mensah
Affiliation:
Faculty of Agriculture, University of Swaziland, Luyengo Campus, Swaziland
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Abstract

Field trials were carried out for two seasons on the effect of insecticides on insect pests, damage and yield of three cowpea cultivars.

During the first season, the preflowering stage of crop growth was found to be infested by Aphis spp, Empoasca spp, Ootheca spp and Epilachna spp, the flowering stage by Megalurothrips sjostedti, Heliothis armigera, Astylus atromaculatus, Coryna kersteni and Mylabris amplectens and the postflowering stage by H. armigera and a number of coreid and pentatomid bugs. Fenthion gave the least protection against pod damage by H. armigera. There were significant increases in the number of harvestable pods per plant with insecticides. There were no significant differences in hull weight and shelling percentage. Grain yield was increased by 96.2 and 109.4% after treatment with dichlorvos and cypermethrin, respectively.

In the second season, cypermethrin and monocrotophos were most effective. Cypermethrin reduced the number of pod-sucking bugs by 58%, H. armigera by 93%, while monocrotophos reduced Empoasca spp by 39% and M. sjostedti by 79%. Cypermethrin reduced damage by pod-sucking bugs by 28%, and by H. armigera by 95%. Monocrotophos reduced damage by pod-sucking bugs by 14%, and by H. armigera by 80%. Significant increases in the number of harvestable pods per plant were obtained with monocrotophos and cypermethrin treatments. There were no significant differences between the number of seeds per pod, and the weight of 1000 seed-grains. Grain yield was increased by 55.4% after both cypermethrin and monocrotophos treatment. The application of these insecticides were financially beneficial but the gain was reduced when six sprays were applied. Cypermethrin and monocrotophos are promising insecticides for controlling insect pests on cowpeas.

Résumé

Des études aux champs ont été menées pendant deux saisons afin d'évaleur l'efficacité des insecticides contre des insectes, leurs effets nefastes et la recolte sur trois variétés de haricot.

Pendant la première saison, les plantes ont été infestées par Aphis spp, Empoasca spp, Ootheca spp et Epilachna spp avant la fleuraison, par Megalurothrips sjostedti, Heliothis armigera, Astylus atromaculatus, Coryna kersteni et Mylabris amplectens pendant la fleuraison, et par H. armigera et un nombre de bruches du type coreid et Pentatomid après la fleuraison. Fenthion était moins protectrice contre les attaques de H. armigera. L'application des insecticides a donné lieu à des augmentations de nombre de cosses recoltés par plante. On a pas constaté de difference significative en ce qui concerne le poids brut et le pourcentage d'egrenage. La récolte a été considerablement augmentée de 96.2 et 109.4% après traitement avec dichlorvos et cypermethrin respectivement.

Au cours de la deuxième saison, cypermethrin et monocrotophos se sont reveles les plus efficaces.

L'application de cypermethrin a diminué de 58% le nombre des insectes qui attaquent les cosses et de 93% en ce qui concerne H. armigera tandis que la reduction de nombre des insectes par monocrotophos était de 39% pour Empoasca spp et de 79% pour M. sjostedti. Le traitement par cypermethrin a diminué de 28% les attaques par les bruches attaquant les cosses et de 95% par H. armigera. Quant au traitement par monocrotophos la diminution était de 14% pour les bruches attaquant les cosses et de 80% pour H. armigera. Des augmentations significatives de nombre de cosses recoltés par plante ont été obtenu avee monocrotophos et cypermethrin. Aucune difference significative n'a été observée entre le nombre de grains par cosse, soit le poids raméné à 1000 grains. La récolte a été augmenté de 55.4% après traitement avec cypermethrin et séparément avec monocrotophos.

L'application de ces insecticides a été financièrement bénéfique mais le gain a été réduit lorsque six arrosages ont été effectués. Cypermethrin et monocrotophos sont des insecticides de promesse pour le contrôle de pestes qui attaquent les haricots.

Keywords

Field trialscowpea cultivarsinsecticide spraysinsect pestsinsect damageyieldÉtudes aux champsvariétés de haricotsaerosols d'insecticidesinsectes pestesattaques d'insectesrecolte evaluation
Type
Research Articles
Information
International Journal of Tropical Insect Science , Volume 9 , Issue 1 , February 1988 , pp. 101 - 108
Copyright
Copyright © ICIPE 1988

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