Abstract
Many plant derived botanical insecticides have been identified to replace the use of synthetic insecticides for the control of cowpea in storage. In this regard, it seems essential that any potential substances for use as insecticides should be tested not only for its effectiveness but also for the possibility of the pest developing resistance. A laboratory experiment was carried out to select for resistance in Callosobruchus maculatus using sub-lethal doses of well researched insecticidal plants, West African brown pepper, Piper guineense and Eugenia aromatica. Adult C. callosobruchus were exposed to sub-lethal doses of P. guineense and E. aromatica separately. It was observed that the survival of C. maculatus to the treatment was highly significant in the F4 and F5 generations when treated with 0.2g of sub-lethal dose of E. aromatica. Also C. maculatus showed the highest level of resistance at the F4 and F5 generation when treated with 0.2g of sub-lethal dose of P. guineense. Subjecting egg and larvae of selected population of C. maculatus to the same treatment of plant powders, it was observed that the number of adult that emerged from the selected population was significantly lower than that obtained from the control, which means that resistance in adult stage of C. maculatus does not mean that egg and larvae would also show resistance to the plant powders. This study showed that before build of resistance by weevils, E. aromatica and P. guineense powder is an effective fumigant for disinfecting cowpea seeds against C. maculatus in storage containers.
