Low-lethal and intergenerational effects of broflanilide on the diamondback moth, Plutella xylostella (L.)

The diamondback moth (DBM), Plutella xylostella (L.) is an important agricultural pest worldwide that causes substantial damage to cruciferous crops. Broflanilide is a novel insecticide with high activity against DBM. This study demonstrated that exposure of DBM larvae to low concentrations (LC₅, LC₁₀, and LC₃₀) of broflanilide significantly affected their development and fecundity. These treatments prolonged larval and pupal durations by 13.77% - 23.34% (14.95 h - 25.34 h) and 16.15% - 19.06% (13.46 h - 15.89 h), respectively, and reduced fecundity by 10.59% - 17.10%. The juvenile hormone (JH) titer was increased by 16.15% - 34.31% (LC₅ - LC₃₀). Meanwhile, the expression levels of basic juvenile hormone-suppressible protein 2 (PxBJSP2) and juvenile hormone esterase (PxJHE) were reduced by 41.94% - 52.96%, and 52.43% - 60.19% at LC₅ - LC₃₀ broflanilide treatment. The functions of PxBJSP2 and PxJHE were validated using RNA interference (RNAi). Silencing of these two genes resulted in 35.99% and 49.49% increases in JH titer, respectively. Furthermore, intergenerational effects were observed in the F₁ progeny: the intrinsic rate of increase (r) and finite rate of increase (λ) were reduced by 6.90% - 17.24%, and 2.24% - 5.22%, respectively, while the mean generation time (T) was prolonged by 8.74% - 14.99% (34.56 h - 59.28 h). Broflanilide induced multiple physiological effects by regulating the expression of PxBJSP2 and PxJHE genes in DBM, ultimately suppressing population growth across generations. The intergenerational effects of broflanilide on DBM suggest that broflanilide has great potential for sustainable management of DBM populations.