DIFFERENCES IN THE SUSCEPTIBILITY OF SEEDS OF SELECTED VARIETIES OF COWPEA TO BRUCHIDIUS-ATROLINEATUS (COLEOPTERA, BRUCHIDAE)

The bruchid Bruchidius atrolineatus (Pie) causes significant damage to the stored protein rich seeds of cowpea, Vigna unguiculata, in the We st African Sahel. Twenty varieties of cowpea were evaluated for suscep tibility to attack by B. atrolineatus in the laboratory. The bruchid s howed differential response to the seeds in terms of developmental per iod, percentage adult emergence, seed weight loss due to feeding by on e larva, adult weight at emergence and life-time fecundity of females reared from them. Based on these criteria IT85F-2205 and IT84S-275-9 w ere the least susceptible varieties. The development of B. atrolineatu s 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 IT 84D-460 also had relatively lower susceptibility to the beetle than ot hers. In a no-choice oviposition experiment, B. atrolineatus females l aid equally on all varieties. Percentage egg hatch on the different co wpea varieties did not differ significantly. The results are discussed in relation to previous reports on susceptibility of cowpea and other legumes to bruchids.