Cross‐resistance and baseline susceptibility of Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) to cyantraniliprole in the south of China

The oriental leafworm moth, Spodoptera litura Fab. (Lepidoptera: Noctuidae), is a widely distributed polyphagous insect pest in Asia that has been shown to be resistant to various types of insecticide. The newly registered anthranilic diamide cyantraniliprole provided novel insight and great opportunities to control S. litura.In this study, the susceptibilities of S. litura collected from South China to cyantraniliprole were measured by standard leaf-disc bioassay, and obvious variation in susceptibility was observed among the 17 field populations, with LC50 values varying from 0.206 to 1.336 mg AI L(-1). Significant correlations were detected between the LC50 values of cyantraniliprole and chlorantraniliprole (P < 0.05). However, no significant correlation (P > 0.05) was observed between the two anthranilic diamides and other insecticides with different action mechanisms (delcamethrin, chlorpyrifos, indoxacarb and emamectin benzoate). Piperonyl butoxide showed obvious synergism in Lab-Sus, ZC14 and cyantraniliprole-resistant strains, while diethyl maleate and S,S,S-tributylphorotrithioate had no obvious synergistic effects in any of the strains tested.These results revealed obvious regional variation in cyantraniliprole susceptibilities among populations of S. litura from different areas, and potential cross-resistance to chlorantraniliprole, which suggested that S. litura could develop resistance to cyantraniliprole. Detoxification enzymes might not be involved in the observed tolerance in field-collected populations and the cyantraniliprole-resistant strain.