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Broflanilide is a novel insecticide with a unique mode of action on the insect GABA receptor and is registered worldwide for the control of agricultural pests. It shows high efficacy in controlling the fall armyworm (FAW) Spodoptera frugiperda, which is a destructive pest to various crops. FAW were exposed to sublethal concentrations of broflanilide to determine its impact on insect development. Sublethal doses (LD10 and LD30) caused failure of ecdysis, reduced body length of larvae, malformation of pupae, and vestigial wing formation in adults. Also, broflanilide at LD30 significantly reduced the amount of molting hormone (MH) . After exposure to LD10 or LD30 broflanilide, expression of five Halloween genes, which participate in MH biosynthesis, were found to be altered. Specifically, the transcript levels of SfrCYP307A1 (Spook), SfrCYP314A1 (Shade) and SfrCYP315A1 (Shadow) in 3rd day larvae were significantly decreased as well as SfrCYP302A1 (Disembodied) and SfrCYP306A1 (Phantom) in 5th day pupae. In contrast, the transcript levels of SfrCYP302A1 in 3rd day larvae, SfrCYP307A1 and SfrCYP314A1 in 5th day pupae, and SfrCYP306A1, SfrCYP307A1 and SfrCYP315A1 in 0.5th day adults were significantly increased. Our results demonstrate that broflanilide caused the failure of ecdysis in FAW possibly by influencing the intake of cholesterol through inhibition of feeding and also via altering expression of genes important for MH biosynthesis.

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 3rd day larvae of FAW, respectively. In the 12-hour-old adults, SfrFPPS1 increased to 1.92-fold in LD30 broflanilide-treated group. Broflanilide induced multiple physiological sublethal effects on the biosynthesis of JH by regulating the expression of SfrFPPS and SfrJHAMT genes in FAW and likely in other insects (both pests and non-target organisms). Therefore, its potential for Integrated Pest Management should be further assessed.

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 3rd day larvae of FAW, respectively. In the 12-hour-old adults, SfrFPPS1 increased to 1.92-fold in LD30 broflanilide-treated group. Broflanilide induced multiple physiological sublethal effects on the biosynthesis of JH by regulating the expression of SfrFPPS and SfrJHAMT genes in FAW and likely in other insects (both pests and non-target organisms). Therefore, its potential for Integrated Pest Management should be further assessed.

Broflanilide is a novel insecticide with a unique mode of action on the insect GABA receptor and is registered worldwide for the control of agricultural pests. It shows high efficacy in controlling the fall armyworm (FAW) Spodoptera frugiperda, which is a destructive pest to various crops. FAW were exposed to sublethal concentrations of broflanilide to determine its impact on insect development. Sublethal doses (LD10 and LD30) caused failure of ecdysis, reduced body length of larvae, malformation of pupae, and vestigial wing formation in adults. Also, broflanilide at LD30 significantly reduced the amount of molting hormone (MH) . After exposure to LD10 or LD30 broflanilide, expression of five Halloween genes, which participate in MH biosynthesis, were found to be altered. Specifically, the transcript levels of SfrCYP307A1 (Spook), SfrCYP314A1 (Shade) and SfrCYP315A1 (Shadow) in 3rd day larvae were significantly decreased as well as SfrCYP302A1 (Disembodied) and SfrCYP306A1 (Phantom) in 5th day pupae. In contrast, the transcript levels of SfrCYP302A1 in 3rd day larvae, SfrCYP307A1 and SfrCYP314A1 in 5th day pupae, and SfrCYP306A1, SfrCYP307A1 and SfrCYP315A1 in 0.5th day adults were significantly increased. Our results demonstrate that broflanilide caused the failure of ecdysis in FAW possibly by influencing the intake of cholesterol through inhibition of feeding and also via altering expression of genes important for MH biosynthesis.