Efficacy of etofenprox against insecticide susceptible and resistant mosquito strains containing characterized resistance mechanisms

tofenprox is a non‐ester pyrethroid insecticide with comparable toxicity and a similar mode of action to other pyrethroids. Cross‐resistance studies on mosquitoes showed no effect of carboxylesterase, elevated esterase, altered acetylcholinesterase or glutathione S‐transferase‐based resistance mechanisms on etofenprox toxicity, when compared to standard susceptible strains of Anopheles and Culex. Cross‐resistance to etofenprox occurred in a pyrethroid‐resistant strain of Culex quinquefasciatus with both oxidase and ‘kdr’‐like resistance mechanisms. Dose–response data for susceptible mosquito strains suggest that, in standard W.H.O. susceptibility tests of adult mosquitoes, appropriate discriminating concentrations of etofenprox for detection of resistance would be 0.1% for Culex and 0.25% for Anopheles.