Some observations on the joint action of insecticides upon adult mosquitoes

Abstract

SUMMARYThe joint action of insecticides on adult female mosquitoes, Aedes aegypti and Anopheles stephensi, has been studied by topical applications of known dosages separately and in mixtures. Results indicated that the two organophosphorus compounds, malathion and diazinon, have a similar action on the mosquitoes. Responses to mixtures of an organophosphate (malathion) and a carbamate (Sevin), an organo‐phosphate (malathion) or a carbamate (Sevin) and a chlorinated hydrocarbon (DDT or dieldrin), and of two chlorinated hydrocarbons (DDT and dieldrin) were less than expected for similar action.In other experiments in which two insecticides were applied separately with an interval of 48 hr. between treatments, the order of application was of importance. Mosquitoes receiving a sublethal dose of malathion were more susceptible to Sevin, DDT and dieldrin than untreated mosquitoes from the same population, whereas pre‐treatment with Sevin did not influence susceptibility to malathion, DDT and dieldrin.