A note on simple biochemical methods for resistance detection and their field application in Sri Lanka

Insecticide resistance is conferred by a limited number of clearly defined mechanisms. Previously, resistance detection in field populations of insects was confined to bioassays, which gave information limited to the presence of resistance to the insecticide tested. Biochemical tests have now been introduced into the field in Sri Lanka, which give information on the underlying mechanism of resistance. These tests, as well as being cheap and easy, work at the level of the individual insect and hence give information on the spectrum of resistance, the level of resistance and the frequency of resistance genes in field populations. In Sri Lanka, a malathion‐specific carboxylesterase has been detected in Anopheles culicifacies, an altered acetylcholinesterase in Anopheles nigerrimus and oxidase and glutathione S‐transferase based mechanisms in Anopheles subpictus. The selective advantage of resistant individuals under field insecticide spraying regimes has been estimated, and the relative importance of larval and adult insecticide selection assessed.