Pesticide resistance mechanisms produced by field selection pressures on Anopheles nigerrimus and A. culicifacies in Sri Lanka.

In Sri Lanka, Anopheles nigerrimus is resistant to a range of organophosphate and carbamate insecticides at both the larval and adult stages. Biochemical studies indicate that an alteration in acetylcholinesterase is the basis of resistance rather than increased metabolic breakdown of the insecticides. In contrast, A. culicifacies is resistant only to malathion and closely related compounds containing a carboxylate ester bond. Agricultural pesticides are the sole source of selection pressure for resistance in A. nigerrimus, while in A. culicifacies pressure arises predominantly from antimalarial spraying.