Evaluation of Callosobruchus maculatus (F.) susceptibility to neem (Azadirachta indica A. Juss) seed oil on different cowpea (Vigna unguiculata (L.) (Walp.) cultivars

Abstract

The susceptibility of Callosobruchus maculatus (F.) to cowpea grains exposed to neem (Azadirachta indica A. Juss.) seed oil (NSO) was evaluated. About 15 g cowpea grains each of two improved varieties (1T97K-499-35 and 189KD-288) and three local cultivars (Kanannado white, Banjara and Borno brown) were treated with freshly extracted NSO at four dosages 0.00 or untreated/control, 0.02, 0.04 and 0.08 mL. Each treatment was replicated four times and the experiment laid out in a completely randomized block design. Data obtained were subjected to the analysis of variance and significant means were separated at 5% level using the least significant difference test. The mean number of eggs laid, emerged adults, percentage grain damage, severity of grain damage, susceptibility index and developmental period of C. maculatus were significantly lower on all cowpea cultivar treated mainly with 0.04 and/or 0.08 mL NSO/15 g than the untreated ones. Overall, cowpea cultivar performance was in the order 189KD-288 ‰¥ IT97K-499-35 ‰¥ Kanannado white ‰¥ Borno brown ‰¥ Banjara. The use of resistant varieties should be promoted in managing C. maculatus devastation of stored cowpea under subsistence farming conditions. Furthermore, present information may be used as a tool in grain breeding programmes for C. maculatus and integrated management programmes.