Extent Of Resistance

In some insects, resistance extends only to a few closely related compounds in a single chemical class. It may be very weak or restricted to a small part of the insects' geographical range. At the other extreme, some widespread pests, such as anopheline mosquitoes (e.g., Anophelesgambiae), the diamondback moth (Plutella xylostella), the Colorado potato beetle (Leptinotarsa decemlineata), and the sweet potato whitefly (Bemisia tabaci) now resist most or all of the insecticides available for their control. The most extensively used insecticide classes—organochlo-rines, organophosphates, carbamates, and pyrethroids—have generally been the most seriously compromised by resistance, and many principles relating to the origin and evolution of resistance can be demonstrated solely by reference to these fast-acting neurotoxins. In recent years, however, there has also been a worrying increase in resistance to more novel insecticides. These include compounds attacking the developmental pathways of arthropods (e.g., benzoylphenylureas), their respiratory processes [e.g., mitochondrial electron transport inhibiting (METI) acaricides], their digestive systems [e.g., Bacillus thuringiensis (Bt) endotoxins], and pathways associated with the regulation of their nervous processes (e.g., neonicotinoids).

0 0

Post a comment