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Abstract Sitophilus and Callosobruchus species are major pests of stored grains and grain products in the tropics and sub-tropical regions. The cowpea beetle, Callosobruchus maculatus (F.) (Coleoptera: Bruchidae), is a cosmopolitan field-to-store pest ranked as the principal post-harvest pest of cowpea in the tropics. It causes substantial quantitative and qualitative losses manifested by seed perforation and reductions in weight, market value and germination ability of seeds. The rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), is another important stored-grain pest. This species feeds on a variety of cereals or grains, particularly wheat and rice, which are among the most frequent sources of nutrition. Control of these insects relies heavily on the use of synthetic insecticides and fumigants, which has led to problems such as disturbances of the environment, increasing costs of application, pest resurgence, pest resistance to pesticides and lethal effects on non-target organisms in addition to direct toxicity to users (Jembere et al., 1995; Okonkwo and Okoye, 1996). Thus, repellents, fumigants, feeding deterrents and insecticides of natural origin are rational alternatives to synthetic insecticides. Herbal products are one potentially important source. Essential oils are secondary metabolism products in plants. These oils have strong aromatic components that give a plant its distinctive odor, favor, or scent (Koul et al., 2008). A strong connection between medicinal and pesticidal plants was reported by several researchers (Yang and Tang, 1988). |