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The Effects of Some Agrometeorological Factors on Fluctuations of the Legume Pod Borer, Maruca Testulalis Geyer (Lepidoptera: Pyralidae), on Two Cowpea Varieties in Nigeria

  • Aliyageen M. Alghali
Research Article

Abstract

An experiment to examine the effects of four agrometeorological factors on population fluctuations in legume pod borer, Maruca testulalis (Geyer) in two cowpea varieties was carried out under field conditions in Ibadan, Nigeria. Plots, 5 × 10 m each, of cowpea varieties IT84S-2246-4 and Dan ilan were planted fortnightly between 5 May and 5 October 1988 (12 plantings in all for each variety). Three peaks of the pod borer populations were observed on the cowpeas. There were smaller peaks on crops planted between 5 May and 1 June and again between 29 June and 13 July and a larger one on those planted between 24 August and 7 September. These two peaks coincided with the peaks of the rainfall.

Significant relationships were obtained between pod borer counts and (a) cumulative rainfall (R2 = 0.41; P = 0.004) (b) number of rainy days (R2 = 0.17; P = 0.04) from plant emergence to 50% flowering. These results suggest though, the distribution of rainfall over time is more crucial than the total amount in determining the fluctuations of pod borer populations. Thus, the adjustment of planting dates is suggested as an IPM tactic to avoid the development of damaging levels of pod borer infestations.

Key Words

Cowpea legume pod barer population fluctuation rainfall 

Résumé

Une expérimentation en plein champ a été conduite à Ibadan, Nigeria, pour déterminer les effets de 4 facteurs agrométéorologiques sur les fluctuations de la population du foreur de gousse, Maruca testulalis (Geyer), dans 2 variétés de dolique de chine (haricot sec). Les varié tés IT84S-2246-4 et Dan ilan ont été plantées à intervalles de 2 semaines entre le 5 mai et le 5 octobre 1988 sur terrains de 5 × 10 m chacun (chaque variété a été plantée 12 fois au total). Trois pics de la population du foreur de gousse ont été observés. Deux pics mineurs sur les plants plantés entre le 5 mai et le 1 juin, entre le 29 juin et le 13 juillet, et 1 grand pic sur ceux plantés entre le 24 août et le 7 septembre. Le 1er et le dernier pic ont coïncidé avec les pics des précipitations.

Une corrélation significative a été obtenue entre le nombre d’insectes et (a) précipitations cumulées (R2 = 0.41, P = 0.004) et (b) le nombre de jours de pluie (R2 = 0.17, P = 0.004), de la germination des plants à la floraison à 50%. Ces résultats suggèrent que les précipitations, bien qu’importantes, leur répartition dans le temps est cruciale dans la détermination de la dynamique de la population du foreur de gousse. Ainsi, l’ajustement des dates de semis est suggéré comme une stratégie de lutte intégrée pour réduire les niveaux de dégâts occasionnés par ce ravageur.

Mots Clés

Dolique de chine (haricot sec) foreur de gousse dynamique de population précipitations 

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Copyright information

© ICIPE 1993

Authors and Affiliations

  • Aliyageen M. Alghali
    • 1
  1. 1.ICIPE/IITA ProjectInternational Institute of Tropical Agriculture (HTA)IbadanNigeria

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