Department of Biology, Federal University of Technology, P.M.B 704, Akure, Ondo State, Nigeria

The efficacy of the powders of Newbouldia laevis (Seem) was tested as grain protectants against infestation by Callosobruchus maculatus (Fab.) on cowpea (Vigna unguiculata L. (Walp) stored for three months at ambient temperature of 28⁰C± 2⁰C and 70 ± 5% relative humidity. Powder from the leaves, stem, root and wood ash were tested at 0.0g (control), 0.1g, 0.2g, 0.3g, 0.4g and 0.5g per 20g of cowpea seeds. Mortality, oviposition and adult emergence of C. maculatus as well as seed damage and weight loss of cowpea varied over the period of storage. 100% mortality of adult beetles was achieved at higher concentrations (0.4 and 0.5g) of the powders within 96hrs of application. This was significantly different (p<0.05) from the control and those obtained at lower concentrations. Mortality however decreased over the three months period of storage at lower concentrations while higher concentrations maintained their effectiveness. Oviposition and adult emergence of C. maculatus were significantly higher (p<0.05) in the control than in treated seeds throughout the period of storage. More eggs were laid at lower concentrations and consequently the percentage adult emergence was higher. Oviposition and adult emergence increased from one to three months of storage. Seed damage and weight loss were significantly higher (P<0.05) in the control than in treated seeds throughout the period of storage. Therefore, the powder of N. laevis could be used to protect cowpea seeds stored for a short period against infestation by C. maculatus and higher concentrations is needed for long-term storage.

Keywords: Newbouldia laevis, Callosobruchus maculatus, oviposition, adult emergence, seed damage, seed weight loss.