Toxicity and persistence of Boscia senegalensis Lam. (Ex Poir.) (Capparaceae) leaves on Callosobruchus maculatus Fab. (Coleoptera:Bruchidae)

Abstract

In this study, we examined the toxicity and persistence of ground fresh leaves of B. senegalensis on the development of Callosobruchus maculatus, major insect pest of cowpea (V. unguiculata) in the sahelian area. The effect of the product has been evaluated over the three developmental stages (egg, larvae and adult) of C. maculatus. At high concentration (4 g/l of ground leaves), 100 % of adults were killed within 24 h of exposure to the leaf extract, and the development of newly laid eggs and neonate larvae was also inhibited. However, the ground leaves of B. senegalensis have a variable efficacy against the bruchid instars larva. The 2nd larvae stage (L2) of C. maculatus developing inside the seeds have proved to be highly susceptible while the 4th larval stage was relatively tolerant. The study of the toxicity persistence of the leaves of B. senegalensis showed that whatever its concentration, the efficacy of crushed leaves of B. senegalensis decreased with the storage time. At a concentration of 20 g/l, the effect of B. seneglensis can persist up to 7 days.Keywords: Biopesticides, Bruchids, cowpea, pest control, Niger