Bio-Efficacy of Cotyledon Oil Extracts and Powders of Melon, Citrillus Vulgaris Schrad against Maize Weevils, Sitophilus Zeamais Motschulsky (Coleoptera: Curculionidae)

Toxicity of cotyledon oil and powder of Melon, Citrullus vulgaris Schrad against Sitophilus zeamais (Motschulsky) was assessed. Cotyledon oil extract of C. vulgaris was mixed with 20 g of maize grains at the concentration rate of 0.5, 1.0, 1.5 and 2.0 % v/w while the cotyledon powder was mixed at the dosage rate of 1.0, 2.0, 3.0 and 4.0 g per 20 g of maize grains. They were all infested with five newly emerged S. zeamais. Untreated experiment was set up as control for all the treatments. All treatments were replicated four times and set up in a Complete Randomized Design. The experiments were observed for 192 h to record mortality. After 192 h the experiments were allowed to stay for another one week after which the grains were stained in gentian violet to reveal egg plugs. Thereafter, the experiments were allowed to stay for another 7 weeks to observe adult emergence. Percentage grain damage and weight loss were calculated after 50 days. Cotyledon powders and oils of C. vulgaris significantly reduced mortality, oviposition and adult emergence. Mortality of treated experiment was 100 % at the concentration rate of 1.0, 1.5 and 2.0 % v/w by 192 h of the experiment while the mortality of powder treated experiment was 100 % at the treatment level of 3.0 and 4.0 g per 20 g of maize grains. Also, oviposition was 0 % at oil extract concentration level of 1.5 and 2.0 % v/w. The oil and powder significantly reduced grain damage.