Effect of Cowpea Trap Crop on the Control of [Aphis gossypii (Glover)] in Zimbabwean Cotton

Cotton aphids are major cotton pests causing significant yield losses of more than 65% in Zimbabwe. Field experiments to investigate the effectiveness of cowpea as a trap crop in reducing aphid pressure on cotton were conducted over three seasons 2010/11 to 2013/14 at Cotton Research Institute (CRI) in Kadoma, and Umguza in Matebeleland North, in Zimbabwe. Incidence of aphid predators on sole cotton, cotton intercropped with cowpea trap crop and the trap crop itself were also assessed. The measurements were aphid scores, aphid predator counts in both sole cotton, intercropped cotton and cowpea trap crop. Seed cotton yield was measured. Aphid scores and predator counts were subjected to Analysis of Variance (ANOVA) using GenStat 14th Edition software. The square root transformation [x + 3/8] was used for scores or counts not normally distributed. At CRI Cowpea trap crop significantly controlled aphids in intercropped cotton better than chemical control using Acetamiprid 20 SP (P< 0.05). Coccinellid grubs (ladybird beetle larval) populations were highest in cowpea trap crop. At Umguza poor germination of cowpea resulted in highest Coccinellid adults (ladybird beetle adults) in intercropped cotton. Yield of intercropped cotton was comparable to yield from plots where Acetamiprid 20SP was used as a standard practice. Farmers can adopt this technology of aphid control in cotton using commercial cowpea variety CBC 3 as cotton aphid trap crop.