Resistance monitoring of Laodelphax striatellus from four regions in eastern China to eight insecticides

In order to clarify the resistance status and resistance mechanism of the field population of the small brown planthopper (SBPH), Laodelphax striatellus, to commonly used insecticides, we monitored the resistance level of SBPH collected from Yizheng and Yancheng in Jiangsu Province, Changxing in Zhejiang Province and Lujiang in Anhui Province, to eight insecticides during 2021 to 2022 using rice seedling dipping method. The synergistic effects of three detoxification enzyme inhibitors, piperonyl butoxide (PBO), diethylmaleate (DEM), and triphenyl phosphate (TPP), to buprofezin on the control of SBPH were measured. The results showed that four regions populations of SBPH have developed medium to high level resistance to buprofezin (RR = 61.5-148.8), and moderate level resistance to chlorpyrifos (RR = 14.9-28.3). Furthermore, the four regions SBPH populations exhibited sensitive or low-level resistance to nitenpyram (RR = 0.7-9.9), thiamethoxam (RR = 1.6-8.3), dinotefuran (RR = 2.9-10.0) and sulfoxaflor (RR = 2.5-8.7). In addition, all field populations of SBPH were susceptible to pymetrozine (RR = 1.0-5.0) and triflumezopyrim (RR = 0.5-2.3). PBO, TPP, and DEM displayed no synergism effect on the sensitivity of SBPH to buprofezin, which indicated that these three detoxifying enzymes might play little role in the buprofezin resistance. The results of this study provided a scientific basis for the resistance management and field control of SBPH.