Susceptibility of Aedes aegypti pupae to neem seed kernal extracts

Abstract

Laboratory bioassays were conducted to evaluate the pupicidal activity of neem (Azadirachta indica) seed kernel extracts (NSKE) on Aedes aegypti. The neem seed kernel powder was sequentially extracted with hexane, benzene, ethyl acetate, acetone, DMSO, 2-propanol, ethanol, methanol and dstiledwater. Ten concentratons (0.0, 0.25, 0.5, 1.0, 2.0, 4.0, 50, 10.0,15.0 and 20.0%) of the neem extracts were used for the bioassays. Each treatment was replcated five times. Twenty-laboratory strains of Aedes aegypti pupae were exposed to each concentration Pupae were not fed durng the exposure periods. Pupal mortality was assessed after 1 and 24 hoursof exposure. The results of the effects of 1h exposure indicated decreased pupicidal mortality whdecreasing extracts toxicity thus: ethyl acetate (LC₅₀= 0.06%) > acetone > (LC₅₀ = 0.29%) > benzene (LC₅₀ = 0.82%) > hexane (LC₅₀ = 3.13%) and propanol (LC₅₀ = 763%). No pupal mortality was observed with extracts from Dimethyl sulfoxide (DMSO), ethanol, methanol and distilled water. The results of the effect of extract for 24h exposure indicated pupicidal mortality in2-propanol (LC₅₀ = 0.67%) and ethanol (LC₅₀ = 1.70%). No pupcida mortality was observed wth hexane, benzene, ethyl acetate, acetone, Dimethylsulfoxide (DMSO), methano and distiled water extracts. The ability of some neem extracts to kill Aedes pupae at relativey low concentrations presents an alternative to the use of synthetic pesticides for control of mosquitoes. This techniqueis environmental friendly, biodegradable, less expensive, and locally available in mosquito endemicarea. Potentials for adoption in mosquito management programmes cannot be overemphasized.

Keywords: Azadirachta indica, Aedes aegypti, Pupicidal

Animal Research International Vol. 3 (1) 2006 pp. 403-406