HIGH MORTALITY AND REDUCED OVIPOSITION: EFFICACY OF THE LEAF POWDER OF GREENWAYODENDRON SUAVEOLENS (ENGL. AND DIELS) VERDC. (ANNONACEAE) AGAINST CALLOSOBRUCHUS MACULATUS (FAB.) (COLEOPTERA: CHRYSOMELIDAE)

Abstract

Increasing evidence suggests that the use of synthetic insecticides in controlling stored product pests poses significant threats to human health and food security. Although the use of indigenous plants in the control of stored product pests have been widely suggested, only a few empirical evidence exists on the efficacy of these plant species. This study investigated the efficacy of the leaf powder of an indigenous plant, Greenwayodendron suaveolens (Engl. & Diels.) Verdc. (Annonaceae) against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) infesting stored cowpea. Ten pairs of sexed freshly emerged adults of C. maculatus were exposed to the leaf powder of G. suaveolens at the rates of 0.0, 2.5, 5.0, 7.5g/40 g cowpea seeds in plastic containers. Adult beetle mortality was monitored every 24 hours for 7 days. All rates of treatments elicited significant mortality in adult C. maculatus. Results indicated over 80% mortality 7 days after infestation. Beetle mortality increased with increasing period of exposure to the leaf powder. It was observe that 2.5 g of the leaf powder significantly reduced oviposition by 60%. The results suggest that the high adult mortality and the reduction in oviposition rate caused by the leaf powder of G. suaveolens could be attributed to the presence of one or more bioactive compounds as has been documented in other members of the family Annonaceae. Consequently, it is hypothesized that the leaf powder of G. suaveolens can be used as an alternative to conventional insecticides owing to its lack of residual effect, low cost, easy mode of preparation and application