Broflanilide prolongs the development of fall armyworm Spodoptera frugiperda by regulating biosynthesis of juvenile hormone

Abstract

Broflanilide, a novel meta-diamide insecticide, has been registered worldwide to control agricultural pests, and cause negative influence to insect under not only lethal but also sublethal level in the field. Fall armyworm (FAW) Spodoptera frugiperda is a worldwide distributed insect frequently controlled by using insecticides, and the potential regulating mechanism of broflanilide on this key insect prompt careful characterization. In the present study, we exposed FAW larvae to sublethal dose (LD5), low lethal doses (LD10 and LD30) and median lethal dose (LD50) of broflanilide and measured various subsequent physiological sublethal effects. FAW larvae body length became shorter (LD5-LD50), the larvae and pupae duration were increased by 0.96-4.63 days (LD5-LD50), and the juvenile hormone (JH) titer significantly increased up to 134.46% (LD10-LD30). Meanwhile, the JH acid methyltransferase gene (JHAMT) and farnesyl diphosphate synthase 1 (FPPS1), which are critical enzymes of JH biosynthesis, increased by 2.07-and 2.18-fold in LD10 broflanilide-treated group, and by 2.22-and 1.78-fold in LD30 broflanilide-treated group in 3 rd day larvae of FAW, respectively.