Laboratory evaluation of six improved cowpea Vigna unguiculata varieties for susceptibility to seed beetle, Callosobruchus maculatus (Coleoptera: Chrysomelidae) in Storage

Laboratory experiments were carried out to evaluate the susceptibility of six improved cowpea varieties to seed beetle, Callosobruchus maculatus (Coleoptera: Chrysomelidae) attack at a temperature of 29 ± 2 °C and a relative humidity of 65 ± 3%. Fifty grams of each variety were weighed in Kilner jars (250ml) and infested with three females and two males of C. maculatus that were 1-2 days old. Data recorded were the physical characteristics of the cowpea varieties, number of eggs laid, percentage egg survival, number of emerged adults, duration of emergence (DE), mean developmental period (MDP), percentage seed weight loss, percentage seed damage and susceptibility index. The experiment was a completely randomised design with three replications. Results showed that significant differences (p 0.05) existed in DE and MDP among the cowpea varieties studied. IT90K-76, IT98K-131, IT11D-15-21 and IT07K-299-6 performed significantly better in duration of emergence than IT10K-866-1 and TVx 3236. IT98K-131-1 performed significantly better in median developmental period (26.67 days) than other varieties except for IT90K-76 (22.67 days). Results showed that IT90K-76, IT10K-866-1 and IT98K-131-1 were moderately resistant while IT07K-299-6, IT11D-15-21 and TVx 3236 were susceptible. This study recommends IT90K-76 because it performed appreciably better in these parameters than the other cowpea varieties when infested with C. maculatus in storage.