Resistance monitoring of diamide insecticides and characterization of field-evolved chlorantraniliprole resistance among Chinese populations of the tomato pinworm Phthorimaea (=Tuta) absoluta (Lepidoptera: Gelechiidae)

The tomato pinworm, Phthorimaea (=Tuta) absoluta, is considered one of the most destructive and invasive insect pests worldwide, having developed significant resistance to many popular insecticides. In this study, we monitored the field resistance of P. absoluta populations from China to three diamide insecticides: flubendiamide, chlorantraniliprole, and cyantraniliprole. We found that one field population from Wuzhong City (WZ) exhibited high level of resistance to chlorantraniliprole. Using the WZ population and a susceptible reference strain (YN-S), we established a near-isogenic line (WZ-NIL) of P. absoluta with resistance to chlorantraniliprole. This strain also showed substantial cross-resistance to flubendiamide, and cyantraniliprole. Genetic analysis revealed that the inheritance of resistance to chlorantraniliprole in the WZ-NIL strain was autosomal and incompletely dominant. Additionally, the pesticide synergist piperonyl butoxide significantly inhibited chlorantraniliprole resistance by compromising P450 monooxygenase activity, which was significantly higher in the resistant strain. Furthermore, WZ-NIL had significantly prolonged developmental stages, lower pupation rates, reduced female fecundity, and lower egg hatchability than YN-S individuals. The fitness of WZ-NIL relative to YN-S was estimated to be 0.73, indicating significant fitness cost associated with chlorantraniliprole resistance. Rotating chlorantraniliprole with other insecticides that have different modes of action and degradation may be particularly useful for managing chlorantraniliprole resistance in P. absoluta.