Association of esterases in resistance to naled and resmethrin in field-collections of the southern house mosquito, Culex pipiens quinquefasciatus (Diptera: Culicidae)

Biochemical and biological assays were used to characterize insecticide resistance in adults from multiple populations of Culex pipiens quinquefasciatus (Say) collected from East Baton Rouge Parish. Based on bioassays using discriminating concentrations, frequencies of insecticide resistance varied from 4-100% for resmethrin, and 88-100% for naled. In addition, elevated esterase activities toward α- naphthyl acetate were associated with increased frequencies of resistance in some, but not all, wild populations. Finally, naled synergized the toxicity of resmethrin up to 2.6-fold in populations with increased esterase activity but had a slight antagonistic effect on the susceptible, Sebring-S strain. Results from these studies are discussed with respect to current management strategies for this species.