Thermal behaviour and biological activity against Aedes aegypti (Diptera: Culicidae) of permethrin and pyriproxyfen in a smoke-generating formulation

Abstract

Background: The most common ways to control dengue vector Aedes aegypti (L.) are larval source reduction in domestic habitats and ground application of small quantities of aerosol insecticide (ultralow volume). Nevertheless, these actions have been shown repeatedly to be ineffective in controlling Ae. aegypti populations. Results: The efficacy of a new smoke-generating formulation containing pyriproxyfen and permethrin was evaluated in the laboratory. Smoke-generating tablets containing each insecticide individually or combined were prepared, and the recovery of the insecticides from the smoke was determined. Recovery values of over 90% were obtained for pyriproxyfen, and around 50% for permethrin. The biological efficacy of pyriproxyfen released in the smoke was evaluated in the laboratory, on late third-instar or early fourth-instar Ae. aegypti larvae, using different concentrations of pyriproxyfen and exposure times. Adult emergence inhibition (EI) values of 100% were obtained at 30 min, and a dose-dependent effect was observed at 5 min. The effect ofpyriproxyfen releasedin thesmokewas duetodirect contact with thelarvicidein thewater ratherthan byinhalationof the fumes. The efficacy of permethrin released in the fumes was also evaluated as knockdown effect (KT50) on adults for a tablet containing permethrin alone or permethrin plus pyriproxyfen. There was no significant difference in KT50 values obtained for permethrin (KT50 = 19.9 min) and permethrin plus pyriproxyfen (KT50 = 19.4 min). Conclusion: The excellent laboratory performance of this new formulation on immature stages and adults indicates that a smoke-generating tablet containing pyriproxyfen and permethrin could be a new tool for controlling mosquitoes.