Bioactivities of crude extracts of the candlewood Zanthoxylum xanthoxyloides Lam. (Rutaceae) against the cowpea beetle Callosobruchus maculatus (Walp)

The efficacy of petroleum-ether crude extracts of the candlewood, Zanthoxylum xanthoxyloides Lam. was assessed for their contact toxicity, feeding and oviposition deterrence to the cowpea beetle Callosobruchus maculatus (Walp). Percent mortality, number of progeny produced and damage caused to were dose– dependent. Root extracts was the most effective as toxicant to the beetles. The LD50 in 24 h topical application of root extracts was 4.98 μg. The LD50 (96 h toxicity in grain) suggests that root extract was highly toxic to C. maculatus. Development of eggs and larvae within grain kernels, as well as progeny emergence were significantly inhibited in treated grains. There were no progeny produced by C. maculatus in grains treated with dosage ³ 0.4 g per 100 g of grain. Root extracts provided the greatest protection of cowpea against feeding by C. maculatus with no observable feeding damage to grains treated with the highest dosages of the three materials. Extracts were repelled C. maculatus but with considerable variation in their repellent action. Z. xanthoxyloides contains phytochemicals, and crude extracts could be used as a botanical insecticide in alternative control strategies against C. maculatus. Keywords: Antifeedant, Bruchids, Botanical insecticides, Reproduction retardant, Toxicity. Int. J. Biol. Chem. Sci. Vol. 2 (3) 2008: pp. 316-32