Laodelphax striatellus Fallén is one of the main pests that can severely harm rice, corn, and wheat. Insecticides acting on the nicotinic acetylcholine receptor (nAChR) are the main type of pesticides used for the control of L. striatellus in Shandong Province, a major grain-producing region in China. In this study, the rice seedling dipping method was used to determine the sensitivities of six field L. striatellus populations in Shandong to seven insecticides acting on nAChR. The results showed that all the field populations were sensitive to clothianidin, nitenpyram, and triflumezopyrim, and the Jiaxiang population exhibited the lowest resistance ratio (RR) to imidacloprid, dinotefuran, sulfoxaflor, and thiamethoxam. The Donggang population showed a medium-level resistance to imidacloprid, with the highest RR of 17.48-fold. The Yutai population showed low-level resistance to imidacloprid and thiamethoxam, with RRs of 7.23- and 7.02-fold, respectively. The contents of cytochrome P450 monooxygenase (P450s), carboxylesterase (CarE), and glutathione S-transferase (GST) were the highest in the Donggang population and the lowest in the Jiaxiang population. The P450 gene CYP314A1 and the CarE gene LsCarE12 were highly up-regulated in all populations. No mutations of V62I, R81T, and K265E in the nAChR β1 subunit were found in any of the populations. These results provide valuable information for the strategies of resistance management of L. striatellus in the field.
Keywords: Laodelphax striatellus Fallén; biochemical characteristics; nicotinic acetylcholine receptor; sensitivity.