Pest management in cowpea. Part 3. Quantifying the effect of cowpea field pests on grain yields in eastern Uganda

We used regression analysis to quantify yield variations in cowpea due to m ajor insect pests, i.e., aphids (Aphis craccivora Koch), thrips (Megaruloth rips sjosredti Trybom), Maruca pod borer (Maruca vitrata Fabricius) and a c omplex of pod-sucking bugs. Variability in pest infestation was created by growing Ebelat (an erect cowpea cultivar) in two locations over three seaso ns and under different insecticide spray schedules. Stepwise regression for individual locations and seasons' data indicated that most of the variatio n in cowpea grain yields was caused by thrips. We estimated that to the tot al variation in cowpea grain yields, on average, the major pests contribute 51-69% in Pallisa and 24-48% in Kumi. Thrips alone contribute 35-41% and 1 3-19% at these two sites, respectively. (C) 2000 Elsevier Science Ltd. All rights reserved.