Phytochemical Composition and Insecticidal Property of Native Plants against the Cowpea Weevil <i>Callosobruchus maculatus</i> Fab. (Coleoptera: Bruchidae) for Natural Preservation of Cowpea Seeds

Abstract

About 80% of cowpea seeds are lost along with 30% of their weight after six months of unprotected storage due to attacks by Callosobruchus maculatus.This study aimed at evaluating the effect of applying bioinsecticides on the biological parameters of C. maculatus to reduce its damage to cowpea stocks.Four treatments including an untreated control and three doses of powdery extracts of C. nigricans, Z. zanthoxyloides and H. suaveolens, were compared in a Fischer block with four completely randomized repetitions. One hundred undamaged cowpea seeds were mixed with doses of each extract in Petri dishes and then fed as food substrates to ten pairs of C. maculatus for eight days. The extracts of H. suaveolens, C. nigricans and Z. zanthoxyloides all contain active ingredients including polyphenols, flavonoids, anthocyanins and alkaloids, etc. The extract of Z. zanthoxyloides was found to be more active on adults (100.00% mortality) followed by C. nigricans (98.75% mortality) and H. suaveolens (97.50% mortality) at 80 mg/g. Fecundity per female decreased significantly in the treated batches of 13.82 eggs for H. suaveolens at 10.12 eggs for C. nigricans at a dose of 80 mg/g.