Yield performance of cowpea as influenced by insecticide types and their combinations in the dry savannas of Nigeria

Insecticide spray offers the most effective control of insect pests where resistant varieties are not available as is the case with the legume pod borer and pod sucking bug complex. Field experiments were conducted in the northern Guinea and Sudan savannas (Samaru and Minjibir, respectively) zones of Nigeria during 2005 to 2007 rainy seasons to evaluate the efficacy of common and new insecticides in the Nigeria markets for field control of insect pests of cowpea. Post spray insect counts showed that the new insecticide combinations gave control of thrips, Megalurothrips sjostedti (Order: Thysanoptera, Family: Thripidae) statistically similar to Monocrophos. Maruca vitrata (Order: Lepidoptera, Family: Crambidae) population densities were significantly reduced by the application of the insecticide regime of Imidacloprid (first spray), Cypermethrin (second and third) which however was not different from Cypermethrin-Dimethoate. The no spray plots gave significantly higher fodder yield in Samaru. The highest mean grain yields at Minjibir were obtained from plots sprayed with Imidacloprid + Cypermethrin + Cypermethrin (1391 kg/ha) while highest mean grain yield (924 kg/ha) in Samaru was from Monocrophos applied three times. Considering safety issues and environmental concerns, Imidacloprid (first spray) and Cypermetrin (second and third sprays) is recommended in a three insecticide spray recommendation for cowpea cultivation, especially in the Sudan Savanna of Nigeria and three sprays of Cypermethrin-Dimethoate in the northern Guinea Savanna