Development of chlorfluazuron resistance and pattern of cross-resistance in the diamondback moth, Plutella xylostella

The rate of development of Chlorfluazuron resistance was investigated in two Thai strains of the diamondback moth (DBM), the TL and BK strains, by laboratory selection. Selection pressure with Chlorfluazuron for 14 and 15 generations has resulted in fairly high levels of resistance. The resistance ratio values have reached 318 and 303 in the TL and BK strains, respectively comparing to nonselected strains. After reaching a considerable level of resistance (more than 200), the selected and nonselected strains were tested for cross-resistance to other insecticides. Except for very low levels of cross-resistance to teflubenzuron (benzoylphenylurea) and pyriproxyfen (juvenile hormone analogue) in the BK and TL strains, respectively, there was no evidence of cross-resistance to other insecticides tested in the two Chlorfluazuron-resistant DBM strains.