Tolerance Activities of Callasobruchus maculatus (F.) (Coleoptera: Chrysomelidae) Against Secamone afzelii (schult) K. Schum Leaf extracts

A laboratory experiment was conducted to investigate the efficacy of methanol and n-hexane leaf extracts of Secamone afzelii against the development and tolerance of the cowpea weevil, Callosobruchus maculatus (F) (Coleoptera: Chrysomelidae) on stored cowpea, Vigna unguiculata (W) seeds. The study was laid out in Completely Randomized Design (CRD) with five pairs of adult beetles exposed to 0.5, 1.0, 1.5 and 2.0 ml corresponding to 2.5, 5.0, 7.5 and 10.0% v/w concentrations admixed with 20g cowpea in three replications under ambient laboratory conditions. Control was also set up with no admixture of extracts. The results revealed that the extracts of the plant exerted significant adult mortality; caused considerable reduction in the number of adult weevil emergence, which ultimately significantly suppressed percentage seed punctured and weight loss. Percentage treatment efficacy showed that the effectiveness of the plant extracts was concentration dependent and seed treated with n-hexane extract recorded the highest bioactivity against C. maculatus compared to ethanol extracts treated seeds. S. afzelii extracts exhibited commensurable pest tolerance activities compared to untreated seeds. It can be used to prevent attack of cowpea by C. maculatus. It might be a good alternative to synthetic insecticides for the protection of cowpea seeds. However, further study is needed to isolate and characterized the bioactive compounds responsible for the plant insecticidal activities.