Resistance, Cross-resistance and Chemical Control of Diamondback Moth in Taiwan: Recent Developments

Except for the chlorinated insecticides, all traditional insecticides and newly introduced IGR-type compounds have been investigated for their modes of action in respect to the resistance in diamondback moth, Plutella xylostella (L.) in Taiwan. Diamondback moth has a very active, efficient, and inducible mixed function oxidases (MFO) system/ complex, which is responsible for the high level of resistance to carbamates, synthetic pyrethroids, and benzoylphenyl urea. Sublines of MFOs respond quickly to the selection pressure of a new type insecticide when its molecular structure fits the substrate for one of the many MFOs. So far, four sublines of MFOs have been found which are responsible for the resistance to common carbamates, carbofuran, all synthetic pyrethroids and benzoylphenyl ureas. The MFO-type resistance in DBM is the worst resistance for insecticides since it would respond indefinitely and render the insecticide useless at any dosage. By investigating the genetic background of different sub-lines of MFOs, a strategy of resistance management has been proposed for benzoylphenyl ureas due to the highly recessive nature of its genes. The same strategy cannot be applied to common carbamates and carbofuran since the responsible MFOs were not recessive. Tactics and strategies of DBM resistance management implementation are collectively discussed.