Phytochemical Constituents and Insecticidal Efficacy of the Root and Leaf Powders of Mimosa diplotricha and Aspilia africana against Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae)

This study investigated the efficacy of the root and leaf powders of Aspilia africana and Mimosa diplotricha against the cowpea beetle, Callosobruchus maculatus. Newly emerged adults of C. maculatus were exposed to grains treated with one of four treatments (powders: 0.5, 1.0, 1.5 and 2.0 g) of the two plants at different exposure period of 24, 48, 72 and 96 hours. Both A. africana and M. diplotricha exhibited a high level of mortality which was a function of treatment concentration and of exposure time. At 96 hours of exposure, 2 g of the root and leaf powders of A. africana caused 70% and 54% mortality respectively, in C. maculatus. When C. maculatus was exposed to 2 g for a 96-hour exposure, the root and leaf powders of M. diplotricha, however, resulted in 52% and 50% mortality respectively. Although powders from all four treatment types exhibited insecticidal activities by causing varying levels of mortality in C. maculatus, the highest death rate was caused by the root powder of A. africana. Qualitative analysis of the plants revealed that alkaloids, flavonoids, saponins, steroids, tannins, terpenoids and glycosides were present in the leaf extracts of A. africana and M. diplotricha. The moderately high insecticidal activity demonstrated by the root powders suggest that they hold more potential in the control of C. maculatus compared to the leaf powders.