Insecticidal Effects of Tephrosia. vogelii Hook (Leguminosae) Leaf Powder and Extracts on Sitophilus zeamais Motsch, Callosobruchus macuIatus F. and Tribolium castaneum Herbst.
DENLOYE, A. A., MAKANJUOLA, W. A., DON-PEDRO, K. N., NEGBENEBOR, H.E.
ABSTRACT. Laboratory bioassays were conducted to investigate the effects of the powder, aqueous and ethanol extracts of Tephrosia vogelii Hook leaf on Sitophilus zeamais Motsch (Curculionidae), Callosobruchus maculatus F. (Bruchidae) and Tribolium castaneum Herbst (Tenebrionidae) in the laboratory at 30 ± 1 -c and 70 ± 2 % RH. Mortality data were recorded and probit analysis run to determine the toxicity of the various formulations. The results showed that the extracts were more toxic to each of the test insect species than the leaf powder. The LCso values obtained for the powder were 10.13 g/kg for C. maculatus; 19.82 g/kg for S. zeamais and 6.85 g/kg for T castaneum. The LCso values obtained for the ethanol extract were 0.037 g/L for C. maculatus, 0.071
g/L for S. zeamais and 0.08 g/L for T castaneum while for the aqueous extract the LCso values were 1.209 g/L for C. maculatus, 0.744 g/L for S. zeamais and 2.025 g/L for T. castaneum. C. maculatus was the most susceptible of the three test insect species to the
ethanol extract. The results indicate that T. vogelii leaf products could be used to protect cowpea, maize or groundnut against C. maculatus, S. zeamais and T. castaneum infestation during storage.