Development and Reversion of Chlorfluazuron Resistance in Diamondback Moth

Selection of two strains (TL and BK) of diamondback moth, Plutella xylostella (L.) with chlorfluazuron has produced high levels of resistance in comparatively short time (9 and 10 generations). The resistance ratio values reached 276and 216-fold, for TL and BK strains, respectively. The BK strain developed about 80-fold resistance level after only three selection generations with chlorfluazuron, suggesting that the resistance gene(s) has, in large measure, been kept in the population. On release from chlorfluazuron selection for two generations, both strains showed no reversion in susceptibility level. Cross-resistance studies revealed very low or no correlation between chlorfluazuron resistance and all insecticides tested in both strains, except teflubenzuron. The two strains showed a slight increase in teflubenzuron resistance level as indicated by resistance ratio values. Heritability (h2) values for the TL strain was significantly higher than that for the BK strain (0.27 for the TLS strain and 0.064 for the BK strain).