Mbatchou V Chi and Sachyere P Apiah
Keywords: Extracts, fractions, toxicants, anti-feedants, % mortality and consumption index.
Abstract: In the present work, two plants Hyptis suaveolens and Hyptis spicigera were studied to identify their toxic and antifeeding effects on cowpea weevils (Callosobruchus maculatus F.). Active ingredients of both plant samples were separately extracted and partitioned using ethanol, chloroform and distilled water solvents. Extracts and fractions obtained were tested on cowpea weevils for toxic and anti-feeding effects using cowpea seeds by two-choices bioassay technique. Results indicated that extracts and fractions from the plant samples were effective in restricting cowpea weevils from feeding on cowpea seeds. Also, extracts and fractions from the plant samples demonstrated cowpea weevil mortalities. These were indications that the plant samples contained toxicants and anti-feedants which prevented the weevils from feeding on the cowpea seeds. Thus, ingredients from Hyptis suaveolens and Hyptis spicigera should be used to protect cowpea seeds and other grains from infestations by Callosobrucus maculatus and other grain infesting insects. Chloroform soluble fraction of the two plants recorded the least percentage consumption index of cowpea seeds and the highest percentage mortality of cowpea weevils which confirmed that it contained the most active ingredients. Hence, chloroform solvent should be used to isolate anti-feedants and pesticide compounds from Hyptis suaveolens and Hyptis spicigera by column chromatographic method.
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