Toxicity of lemon grass powder and methanol extract against Rice Weevi

Objective: to evaluate the toxicity potential of lemon grass [Cymbopogon citratus (C. citratus)] products against adult rice weevil, Sitophilus oryzae. Methods used: Lemon grass (C. citratus) leaves were sun dried for 7 days, pulverized and sieved using 0.5 mm mesh size to obtain fine powders. About 500 g of the powder were dissolved in 1,000 ml of 90% methanol to produce the extract. The powder and extract were used for the bio assay. The powder was tested at 1.0, 1.5, 2.0 and 2.5 g/10 g rice grains, respectively. The toxic potential of the extract of concentration of 1.0, 1.5, 2.0, and 2.5 mg/ml were evaluated using the filter paper method. The experiment was setup on a completely randomized design using three replicates per treatment. Results obtained: The results indicated significant difference (F = 7.450; df = 3.15; P 0.05) in mean percentage mortality after 24, 48, 72, and 96 h exposure with the powder compared with the control. Significantly (F = 5.519; df = 3.15; P 0.05) higher percentage adult mortality was also observed in the extract after 24, 48, 72, and 96 h exposure compared with the control.