Bioactivity of Four Plant Extracts on Coleopterous Pests of Stored Cereals and Grain Legumes in Nigeria

The efficacy of ethanol extracts from four plants,Dennettia tripetala Baker,Eugenia aromatica Baillon,Piper guineense Thonn et Schum and Anchomanes difformis P. Beauv. As bioinsecticides for control of adult Sitophilus zeamais Motschulsky,Tribolium castaneum Herbst,Callosobruchus maculatus Fabricius,Oryzaephilus mercator Fauvel and Lasioderma serricorne Fabricius were determined at two concentrations (0.5% and 2.0%) in the laboratory. All extracts were toxic to beetles with E. aromatica being the most potent of four plant materials tested and had the least LT50 value. This was followed by A. difformis extract. At 2.0% v/w extract concentration, percentage grain damage by insects in treated grains stored for 90 days was nil. Grains protected with A. difformis had the least percentage seed germination of 62.50% while those protected with P. guineense had the highest percentage germination (74.58%) at 2.0% extract concentration. The mean percentage germination in the control was 72.72%. Treatment of grains with plant extracts had no significant (P>0.05) effect on its water absorption capacity.