Larvicidal effect of S-hydroprene and leaf extracts of Azadirachta indica (A. Juss, 1830) on metamorphosis of Culex quinquefasciastus (Say, 1823)

Abstract

Insect Growth Regulators (IGRs) are yet to be explored with the huge Nigerian plant biodiversity despite the bio-specificity and environmental friendly characteristics when compared to conventional chemicals. Safer, cheaper and reachable alternatives to the more popular insecticides that are hazardous to human health and the environment have become imperative. The study was designed to evaluate the effect of S-Hydroprene and various solvent leave extracts of Azadirachta indica on the metamorphosis of Culex quinquefasciastus mosquitoes. Methanol, N-Hexane, Chloroform, Aqueous leave extracts of Azadirachta indica and S-Hydroprene were tested on 1stand 3rdthird instar larvae of Cx. Quinquefasciastus under laboratory conditions for a consistent period of 6 - 15 days in which growth inhibition was monitored using the control to determine the rate of change for the concentrations 10 mg/L, 20 mg/L, 30 mg/L, 40 mg/L, 50 mg/L and 60 mg/L. S-Hydroprene had more deleterious effect on Cx. quinquefasciatus third instar larvae at 60 mg/L 2.8(9%) when compared with methanolic extract. N-Hexane extract killed more larvae at 60 mg/L 11.2(37%). Since extracts of Az. indica had less toxic effect, they allowed for the survival of Cx. Quinquefasciastus but extended the larval stages and prevented ecdysis. The first instar larval stage was maintained for sixteen (16) days which is at variance with the regular three to four days larval existence. Leave extracts of Az. Indica and S-Hydroprene at concentration of 10 mg/L to 60 mg/L caused morphological deformations of the metamorphosis of Culex quinquefasciastus. The leaf extracts of Az. indica possess explorable larvicidal properties for control of larva and adult mosquitoes.