Current resistance status of the brown planthopper Nilaparvata lugens (Stål) to commonly used insecticides in China and Bangladesh

Nilaparvata lugens (Stål) is a serious threat to rice production in Asian countries. Synthetic chemicals are widely used for its control. However, evolution of resistance in this pest to commonly used insecticides has been recorded during the last decades. In this study, we determined and compared current insecticide resistance levels of thirteen N. lugens populations from China and Bangladesh to eight insecticides by rice-stem dipping method. These results showed that N. lugens had developed high levels of resistance to imidacloprid (resistance ratio, RR = 2491.0–8078.5-fold), thiamethoxam (RR = 303.6–1253.6-fold), buprofezin (RR = 175.7–365.1-fold) and dinotefuran (RR = 49.9–596.0-fold), low to moderate levels of resistance to nitenpyram (RR = 12.1–67.3-fold) and sulfoxaflor (RR = 3.8–25.5-fold), but were susceptible to triflumezopyrim (RR = 0.2–1.1-fold) in China. Meanwhile, increased activities of detoxification enzymes (EST, GST and P450) were found in multiple-resistant FY19 field population, which also showed the significant changes in the expression levels of P450s compared to susceptible strain, especially CYP6ER1 (11.04-fold). In contrast, first report of insecticide resistance in Bangladesh showed high levels of resistance to imidacloprid (RR = 3680.1–4430.8-fold) and thiamethoxam (RR = 144.3–737.9-fold), low to moderate levels of resistance to dinotefuran (RR = 38.7–57.9-fold), buprofezin (RR = 28.5–149.1-fold) and nitenpyram (RR = 3.4–14.1-fold). In addition, significant differences in insecticide resistance level of N. lugens to nitenpyram and dinotefuran were observed between two countries in 2020. The present study will be beneficial for implementing effective resistance management strategies to prevent or delay resistance development in N. lugens.