EFFICACY OF THE LEAF POWDER OF AN INDIGENOUS PLANT, OCIMUM GRATISSIMUM (L.) AGAINST CALLOSOBRUCHUS MACULATUS (FAB.) (COLEOPTERA: CHRYSOMELIDAE)

Abstract

The use of botanicals in the control of stored product insects is an ancient tradition and has been practiced for several decades. This study evaluated the toxicity of the leaf powder of an indigenous plant, Ocimum gratissimum (L.) (Lamiaceae) against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae). Toxicity test was evaluated by introducing five pairs of freshly emerged adults of C. maculatus to the leaf powder at the rates of 2.0, 4.0, and 6.0 g per 20 g of cowpea grains. An untreated control was included. Percentage beetle mortality at 24, 48, 72, 96, and 120 hours post treatment was noted and utilized in assessment of the efficacy of the plant powder. The data obtained showed that the leaf powder was effective against the beetles when compared with the control. The highest mortality (100%) was recorded after 120 hours for grains treated with 6.0 g/20 g of the leaf powder followed by those treated with 4.0 g/20 g (84% mortality) and 2.0 g/20 g (72%) while the control recorded zero mortality. The results demonstrated that beetle mortality was dependent on concentration and duration of exposure. The findings of this present study suggest that the leaf powder of O. gratissimum can be used as a potential bio organic pesticide for the control and management of C. maculatus in parts of the world where synthetic pesticides are expensive or impractical