Resistance monitoring of Chilo suppressalis (Walker) (Lepidoptera: Crambidae) to chlorantraniliprole in eight field populations from east and central China

The striped stem borer, Chilo supprressalis (Walker) (Lepidoptera: Crambidae), is a widely distributed pest of rice. Chlorantraniliprole, an anthranilic diamide insecticide, has been widely used to control C. suppressalis in China. However, the control efficacy of chlorantraniliprole in field has greatly decreased in recent years due to strong insecticide selection pressure. Assessment of changing chlorantraniliprole resistance is essential for maintaining control efficiency and resistance management. In this study, we monitored the resistance status of eight C. suppressalis populations from rice fields in east and central China in 2016 using biological, biochemical and molecular genetic assays. The bioassay showed that the eight C. suppressalis populations exhibited moderate to high levels of resistance to chlorantraniliprole, and low to moderate levels of resistance to other two insecticides abamectin and methoxyfenozide in the other classes. The biochemical results indicated that the activities of esterase (EST), glutathione S-transferases (GSTs) and cytochrome P450 ranged from 24.5 ± 2.6 (HY, Hengyang) to 57.7 ± 2.8 (WL, Wenling) nmol/min/mg protein, 49.3 ± 4.7 (HY, Hengyang) to 94.3 ± 2.5 (LY, Longyou), and 1.3 ± 0.1 (XS, Xiaoshan) to 2.4 ± 0.2 (HY, Hengyang). We found that the frequencies of G4946E mutation were 15.0%, 30.0%, 33.4%, 60.0%, 58.4%, 56.7%, 43.4% and 41.7% in the XS, JH (Jinhua), QZ (Quzhou), LY, YQ (Yueqing), WL, HY and XY (Xinyang) populations, respectively. Analysis showed significant correlation between EST activity and toxicity of chlorantraniliprole, but no significant correlation between G4946E mutation frequencies and resistance levels of chlorantraniliprole in C. suppressalis. Hence, we speculate that EST may play a potential role in the development of C. suppressalis resistance to chlorantraniliprole. Our study will enable the development of a more effective resistance management program for C. suppressalis.