Biochemistry of insecticide resistance

After briefly summarizing various resistance mechanisms and their effects on certain types of insecticides, attention is focused on gaps in the understanding of resistance. Most resistance mechanisms consist either of a change in sensitivity of the site of action or an increased capacity for detoxication. In both cases such changes could theoretically be due to quantitative changes of an enzyme (more sites of action or more detoxication enzyme) or to qualitative changes (less-sensitive site of action or more efficient detoxication enzyme). Examples have now been found for each of these possible causes of resistance to insecticides, except for an increased amount of sites of action. Whereas examples of the latter mechanism are known for cell lines resistant to anti-cancer chemicals, so far they have not been found in resistance to insecticides. The impact of the different mechanisms on development and stability of resistance is discussed.