Abstract
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. Key words: Cowpea, Megalurothrips sjostedti, Maruca vitrata, tricel, courage, grain yield.
Highlights
Cowpea [Vigna unguiculata (L.) Walp. (Family: Fabacea)] is an important grain legume in West Africa and in many parts of the tropics (Singh et al, 2002)
Rains generally start in April in the northern Guinea Savanna (Samaru), peaks in August and ends in September with a few showers in October while it starts in May in the Sudan Savanna (Minjibir), peaks in August and ends in September
Significant differences were found among the different environments for number of insect found in cowpea flowers twelve days after insecticide spraying
Summary
Cowpea [Vigna unguiculata (L.) Walp. (Family: Fabacea)] is an important grain legume in West Africa and in many parts of the tropics (Singh et al, 2002). (Family: Fabacea)] is an important grain legume in West Africa and in many parts of the tropics (Singh et al, 2002). The on-farm yields of cowpeas are very low in this region. The low on-farm grain yields averaging 25 to 300 kg/ha in West Africa (Rachie, 1985; Mortimore et al, 1997), and 150 to 400 kg/ha in Uganda (Sabiti et al, 1994) compared to 1500 to 3000 kg/ha in research Institute (Ajeigbe et al, 2005; Singh and Ajeigbe, 2002) are mainly due to a number of insect pests. Edema and Adipala (1996) attributed approximately 70% yield reduction to insect pest alone
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