Spinosad as an Alternative Larvicide for Mosquito Culex pipiens Control

Insecticide resistance has been known to be prevalent in several insect species including mosquito. It has become a major problem in vector control programs due to pesticide resistance through detoxification enzymes. The present study aimed to compare between the larvicidal action of some organophosphorus insecticides (fenitrothion, malathion and temephos) commonly used in larval control programmes and one bioinsecticide (spinosad). Five populations of Culex pipiens mosquito larvae were tested, one was laboratory (reference) population and the other four were collected from El-Fayoum, Giza, El-Sharkia and Kafr El-Shakh Governorates. The highest larvicidal effect was recorded in spinosad treatment followed by temephos, fenitrothion then malathion. Enzyme – based metabolic mechanisms of spinosad were investigated based on the biochemical assay principle against the laboratory population of c. pipiens. The obtained results showed that there were no significant difference in the activity of alfa esterase, acetylcholinesterase and invertase enzymes after the larvae treatment with spinosad while, there were significant differences in protease and beta esterase activities after 6, 24 and 48 hour post treatment, respectively. The use of spinosad as an alternative larvicide was discussed.