Differences in the susceptibility of seeds of selected varieties of cowpea to Bruchidius atrolineatus (Coleoptera: Bruchidae)

The bruchid Bruchidius atrolineatus (Pic) causes significant damage to the stored protein rich seeds of cowpea, Vigna unguiculata, in the West African Sahel. Twenty varieties of cowpea were evaluated for susceptibility to attack by B. atrolineatus in the laboratory. The bruchid showed differential response to the seeds in terms of developmental period, percentage adult emergence, seed weight loss due to feeding by one larva, adult weight at emergence and life-time fecundity of females reared from them. Based on these criteria, IT85F-2205 and IT84S-275-9 were the least susceptible varieties. The development of B. atrolineatus was most significantly delayed in these varieties. The beetle larvae consumed less of their seed material and adults reared from them were smallest and least fecund. The varieties IT87S-1393, IT90K-391 and IT84D-460 also had relatively lower susceptibility to the beetle than others. In a no-choice oviposition experiment, B. atrolineatus females laid equally on all varieties. Percentage egg hatch on the different cowpea varieties did not differ significantly. The results are discussed in relation to previous reports on susceptibility of cowpea and other legumes to bruchids.