Effects of Spinosad and Bacillus thuringiensis kurstaki on Culex pipiens Linnaeus, 1758 (Diptera: Culicidae): Adults' Fertility, Fecundity and Cuticular Hydrocarbons

This study aimed to evaluate the effect of two bacterial preparations: Spinosad and Bacillus thuringiensis kurstaki (Btk), which were applied at low concentrations (20 mu g/l and 23 mg/l, respectively) on L4 larvae of the Culex pipiens. This application was used to assess their effects on mortality of the larvae, reproduction and cuticular hydrocarbons in adults resulting from this treatment. The results showed that both bacteria caused a death rate higher than 80 %, and the sub-lethal doses, despite being less toxic to mosquitoes, caused disturbances in the fecundity and fertility of the adults emerging from treated larvae. The use of sublethal doses of Spinosad induced a quantitative increase in cuticular hydrocarbons at a rate of 36 % to 42 % in treated males and females, respectively. Furthermore, the sublethal dose of Btk causes a reduction in the cuticular hydrocarbons by 59-64 % in both sexes. The results also show that there are no significant differences in the amounts of cuticular hydrocarbons in treated males and females. The results show that the two bacteria are promising as bio-insecticides against C. pipiens and could be good alternatives to chemical pesticides.