Comparative Insecticidal Activities of some Botanical Powders and Pirimiphos-Methyl Against Callosobruchus maculatus Fab.[Coleoptera: Bruchidae] Infesting Cowpea Seeds

Cowpea, Vigna unguiculata [L.] Walp. is a widely planted nutritious grain legume [1]. It is cultivated in many West African countries including Nigeria. Cowpea is a source of dietary protein, vitamins and mineral salts. It has been consumed by human since the earliest practice of Agriculture in developing countries of Africa, Asia, and Latin America [2]. The pulse beetle, Callosobruchus maculatus Fab. [Coleoptera: Bruchidae], is a major pest of economically important grain legume such as cowpea, lentils, green gram and black gram [3-10]. Infestation by C. maculatus starts in the field, where adult females lay eggs on the green pods of cowpea. The larva bore into the pulse grain which becomes unsuitable for human consumption, viability for replanting, or for production of sprouts [11,2,3,13]. The control of infested stored grains by weevils is primarily achieved by the use of convectional insecticides, such as methyl bromide and phosphine. The shortcomings of these convectional insecticides such as environmental pollution, ozone layer depletion of insecticides containing Chlorofloro carbon, human health hazard, among other has led to the ban or restriction of several chemical insecticides [14]. These chemical insecticides are associated with problems such as, lethal effect on non target organisms, pest resurgence, pest resistance and mammalian toxicity due to residue persistence [14-16,6,17]. These aforementioned problems associated with chemical insecticides has led to the search for ecological friendly and cheap control measures [17-19] which include the use of botanical-derived materials such as plant oil extracts, plant crude extracts, plant powders, wood ash e.t.c. Traditional plant materials are sometimes mixed with legume pod or seed in storage for reducing infestation by weevils [20,21]. This work is aimed at determining the comparative insecticidal activities of some botanical insecticide powders and pirimiphosmethyl against Callosobruchus maculatus.