EVALUATION OF SUSCEPTIBILITY OF VARIETIES OF COWPEA TO CALLOSOBRUCHUS-MACULATUS (F) AND CALLOSOBRUCHUS-SUBINNOTATUS (PIC) (COLEOPTERA, BRUCHIDAE)

Twenty-six varieties of cowpea some of which are among those distribut ed for international trials by the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria were evaluated in comparison with Ife Brown, a known susceptible variety, for susceptibility to Calloso bruchus maculatus (F.) and Callosobruchus subinnotatus (Pic.). The mos t susceptible varieties to C. maculatus were TVu 310, TVu 2896, TVu 99 44 and TVu 9836. Some varieties were found to be moderately susceptibl e to C subinnotatus and these included TVu 18, TVu 36, TVu 2896 and IT 81D-1020. Most varieties were found to be more susceptible to C. macul atus than to C subinnotatus. However, the median developmental periods of the bruchids on the cowpea varieties were comparable in most cases . Some varieties were found to be consistently less susceptible to att ack by the two bruchids and these included TVu 2027, IT81D-1064, IT81D -1157 and IT86-498. The weight losses due to infestation by the bruchi ds correlated very strongly to the susceptibility indices (SI) of the varieties to the bruchids. The losses in weight caused by C. subinnota tus were comparable with those caused by C. maculatus even though the number of F1 adults of C. maculatus that emerged from the varieties wa s higher than those of C. subinnotatus.