Sub-lethal effects of broflanilide a novel meta-diamide on Spodoptera frugiperda after long exposure

Abstract

Abstract The fall armyworm (Spodoptera frugiperda) is a polyphagous migratory insect which causes large economic losses in maize. Broflanilide is a novel meta-diamide insecticide with high efficiency to control Lepidoptera pests including S. frugiperda. In this study, broflanilide showed higher toxicity to S. frugiperda larvae (48h LD50, 0.041 μg/g) than commercial insecticides, including emamectin benzoate (0.27 μg/g), spinetoram (0.516 μg/g), indoxacarb (2.507 μg/g), chlorfenapyr (7.143 μg/g), chlorantraniliprole (0.085 μg/g) and lambda-cyhalothrin (0.152 μg/g). For sublethal effect, after being treated by broflanilide with LD30 (0.031 μg/g) dose, for F0 generation, third to sixth instar and total longevity was significantly prolonged by 0.68 days and 4.28 days respectively in the treated cohort and the fecundity of individuals was significantly decreased by 416 eggs per female. For the F1 generation, however, the time from the third to the sixth instar was greatly shortened by 0.91 days, and the number of individuals per female was significantly reduced by 306 eggs. Moreover, we also found that the mRNA expression of the developmental stage related EcR, USP, JHAMT, Vg, CYP306A1 and CYP307A1 genes were significantly decreased in the F0 generation of treated cohort, except CYP18A1. The mRNA expression of the EcR, USP, JHAMT, Vg, CYP18A1 and CYP315A1 were significantly decreased in the F1 generation of a treated cohort, whereas the mRNA expression of the CYP307A1 was significantly increased. The results indicated that a sublethal dose of broflanilide affects the reproduction and development of S. frugiperda, which may be accomplished by influencing the levels of juvenile and molting hormones.