Insecticidal Effects of Hyptis Suaveolens Leaf Extract on Bean Weevils (Callosobruchus Maculatus) and Maize Weevils (Sitophilus zeamais)

Abstract

Hyptissuaveolens is among the most widely used plants in insect pest control.Similarly, the cowpea beetle (Callosobruchusmaculatus F.) is a major primary insect of stored cowpea in Nigeria which causes annual losses estimated at 2900 tons. Likewise, the maize weevil (Sitophiluszemais M.) is one of the world’s most serious stored maize pest, that attacks all other cereal grains and products. The effects of the methanolic, ethanolic and acetonicleaf extracts of Hypitssuaveolens(L.) were evaluated for their repellent activities against adult Callosobruchus maculates and Sitophiluszeamaisusing a multi-choice bio-assay apparatus. The extracts were applied to the cowpea and maize each at 0.00mg/ml, 6.25mg/ml, 12.50mg/ml and 100.00mg.ml concentrations and the repellant activities were recorded. Observations were made after two hours, four hours, six hours, and eight hours for each extract and percentage repellency (PR) was determined. Among the three solvents tested, methanol extract of Hypitsuaveolens (100mg/ml) showed the highest repellent effect on Sitophiluszeamais (100%). In contrast, highest percentage of repellent activity was obtained when acetonicextracts were tested against the cowpea beetles.The highly significant percentage repellency observed in allthe extracts, strongly revealed the repellent properties of the plant. Hypitssuaveolens, is environmentally friendly, safe to consume. Therefore, it is recommended as a promising candidate for the treatment of stored grains.