An evaluation of toxic compounds from Melia dubia (Cav) leaf extract against stored grain pest Callosobruchus maculatus (Fab.)

Abstract

The use of biopesticides is long routed as a viable alternative to synthetic pesticides in integrated pest management. Melia dubia (Meliaceae family) possesses excellent pest management properties based on its secondary plant metabolites. In this study, Melia dubia leaf powders were extracted with different solvents and their phytochemical components identified qualitatively and GC-MS analysis against cowpea beetle, Callosobruchus maculatus. Results revealed that, petroleum benzene and ethanol extracts contained the higher concentrations of terpenoids, fatty acids, phenolic compounds and steroids. Moreover, these extracts contained biopesticides such as thymol, lauric acid, and cholecalciferol. The mortality was recorded after the exposure times of 24, 48 and 72 hours. The highest mortality (87.2±0.8% and LC50 value 16.22 mg/mL) of Callosobruchus maculatus was recorded in Petroleum benzene, followed by ethanol (76.8±0.8% & LC50 value 24.54 mg/mL), water (54.4±0.98% and 44.66 mg/mL) Benzene (41.6±0.98% and 85.11 mg/mL) and chloroform (39.2±0.98% and93.32 mg/mL) after 72 hours. Based on our results, it is concluded that Melia dubia phytocompounds are highly effective in protecting stored grains against Callosobruchus maculatus.