The diamondback moth, Plutella xylostella (L.), is considered one of the most damaging lepidopteran pests, and it has developed resistance to all conventional insecticide classes in the field. Chlorantraniliprole is the first commercial insecticide that belongs to the new chemical class of diamide insecticides. But, P. xylostella have already shown resistance to chlorantraniliprole in China. After 52 generations of selection with chlorantraniliprole, ∼48.17-fold resistance was observed. The resistant strain showed cross-resistance to flubendiamide (7.29-fold), abamectin (6.11-fold), and cyantraniliprole (3.31-fold). Quantitative real-time polymerase chain reaction analysis showed that the expression of the ryanodine receptor gene was higher in the resistant strain than that in the susceptible strain. Enzyme assays indicated that cytochrome P450 activity in the resistant strain was 4.26 times higher compared with the susceptible strain, whereas no difference was seen for glutathione-S-transferase and esterase. Moreover, the toxicity of chlorantraniliprole in the resistant strain could be synergized by piperonyl butoxide, but not by diethyl maleate, and S,S,S-tributyl phosphorothioate. These results can serve as an important base for guiding the use of insecticide in field and delaying the development of pests that are resistant to the insecticides.

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), has evolved resistance to various types of insecticides in the field. In the present study, the resistance of P. xylostella (designated Cya-SEL) to cyantraniliprole increased to 30.6 and 326-fold after 26 generations of selection, compared with the field population (TA) and susceptible population (LAB), respectively. The resistant population also had developed low to moderate levels of resistance to abamectin (3.3-fold), flubendiamide (14.1-fold), and chlorantraniliprole (24.3-fold). Synergism tests indicated that piperonyl butoxide (PBO) and diethyl maleate (DEM) increased the toxicity of cyantraniliprole in the selected strain, i.e., synergism ratio was 2.8 and 3.3-fold, respectively. Reciprocal crosses were made between the susceptible (LAB) and resistant strain collected from Zengcheng (ZC). The degree of dominance and overlapping confidence intervals of LC 50 values of F1 progenies (ZC♀ 9 LAB♂ and LAB♀ 9 ZC♂) suggested an autosomal and incompletely recessive mode of resistance to cyantraniliprole. The test of monogenic inheritance based on a backcross of F1 progeny with the ZC population indicated that resistance to cyantraniliprole was controlled by multiple genes. Additionally, Cya-SEL had a lower reproductive ability and relative fitness than the other tested populations. These findings provide useful information for effective resistance management strategies against P. xylostella.