Comparative Insecticidal Activity and Mechanism of Isocycloseram versus Other GABAergic Insecticides against the Fall Armyworm
Xinyu Liu, Feifan Liu, Tao Tang, Junyan Wang, Ying Wang, Qiu‐Tang Huang, Qiuxia Wang, Chunqing Zhao
Abstract
The fall armyworm (FAW) is a serious agricultural pest and has developed resistance to multiple insecticides. It is necessary to introduce novel insecticide(s) for controlling FAW. Isocycloseram is a completely novel isoxazoline insecticide. However, its activity and mode of action against FAW have not been reported. In this study, isocycloseram exhibited a higher insecticidal activity (LC 50 = 0.26 mg/kg) than fipronil (LC 50 = 7.72 mg/kg) against FAW. The median inhibitory concentration (IC 50 ) of isocycloseram (IC 50 = 8.52 nM) was almost equal to that of the desmethyl-broflanilide (IC 50 = 7.32 nM) to the Sfr RDL1 receptor. The IC 50 of isocycloseram to the Sfr RDL2 receptor was 11.13 nM, which was obviously less than that of desmethyl-broflanilide, dieldrin, fipronil, fluxametamide. Compared with the Sfr RDL2 receptor, the Sfr RDL1 receptor exhibited higher sensitivity to GABAergic insecticides. The recombinant Sfr GluCl receptor was successfully stimulated by l -glutamate; however, the currents were low and weakly inhibited by isocycloseram at 10 μM. In conclusion, our results provided the theoretical basis for usage of GABAergic insecticides for controlling FAW.