Historical changes in the lethal effects of insecticides against the diamondback moth, Plutella xylostella (L.)

BACKGROUND The diamondback moth, Plutella xylostella (L.), is one of the most destructive pests owing to the rapid development of resistance to various groups of insecticides. Although the rotation strategy has become common, resistance management continues to be a critical issue. RESULTS In Japan, historical changes in the susceptibility of P. xylostella to insecticides were estimated using 82 references. The meta-analysis using generalized linear mixed models suggested that each mode of action (MoA) had different patterns of changes to the susceptibility, which might be due to the prevalence of the rotation strategy since the 2010s and the fitness cost of the resistance gene. For example, spinosyns and bacterial insecticide Bacillus thuringiensis (Bt), for which resistance has a high fitness cost, maintained high lethal effects on P. xylostella throughout several decades. However, pyrethroids and benzoylureas, for which resistance has no or little fitness cost, remained at low levels of susceptibility regardless of the rotation strategy. CONCLUSION Our findings suggest optimal combinations of MoA for a sustainable rotation strategy based on their stability and recovery of effectiveness. Susceptibility monitoring using our method and further study of fitness costs will improve the rotation strategy concerning P. xylostella in the future.