Resistance Risk Assessment and Cross-Resistance of Plutella xylostella to Abamectin

A laboratory selection was conducted for Plutella xylostella resistance to abamectin. The results showed that the resistance developed slowly at first and then quickly during the selection. After 14 times of selection during the 20 generations,P.xylostella exhibited 20.92-folds resistance to abamectin compared to the unselcetde parent strain. Estimation of realized heritability (h2) of resistance was studied based on the Tabashnik's method and the h2 for the entire selection experiment was 0.1303. It required 2.4 to 15.9 generations for P.xylostella to obtain 10 fold increase in resistance ratio under selective pressure of 50% to 99% mortality for each selective generation. These results suggested that P.xylostella might have the risk to develop high resistance to abamectin. The susceptibility of the resistant strain to other five insecticides was also tested. The results indicated that the resistant strain had an obvious cross-resistance to emamectin benzoate with a resistant ratio was 8.85 fold,but it had no or low cross-resistance to spinosad,indoxacarb,fiprronil and chlorfenapyr.