Sublethal effects of chlorfenapyr on Plutella xylostella (Lepidoptera: Plutellidae)

BACKGROUND: The diamondback moth (DBM), Plutella xylostella (L.), is the most destructive pest of cruciferous vegetables worldwide. Chlorfenapyr is an important insecticide for controlling DBM. The impacts of three sublethal doses (LC₁, LC₁₀ and LC₃₀) of chlorfenapyr on the chlorfenapyr-exposed DBM individuals and their unexposed F₁ and F₂ offspring were investigated in order to reveal the non-lethal deleterious effects of chlorfenapyr and its potential hormetic effects. RESULTS: LC₁ significantly increased female pupa weight of F₀ and F₁ generations, and F₀ fecundity as well as F₁ gross reproduction rate (GRR). The LC₁-elicited rise in emergency rate and fecundity was significantly greater in F₀ than in F₁. By contrast, LC₃₀ significantly decreased age-specific survival rates, pupation rate, male pupal weight, emergence rate and fecundity of F₀ and F₁ generations as well as female adult proportion and GRR, net reproduction rate (R₀), intrinsic rate of increase (r_m) and finite rate of increase (λ) of F₁ generation. The LC₃₀-induced reductions in pupation rate, adult emergence rate, male and female pupa weight, and fecundity were greater in F₁ than in F₀. While LC₁₀ elicited only a mild inhibition (extension of pupal duration) in F₀, it yielded both deleterious (drops in female proportion and age-specific survivals) and hormetic effects (ups in male longevity and female fecundity) in F₁. CONCLUSION: The results demonstrate that the sublethal effects of chlorfenapyr on DBM vary from inhibition to stimulatory hormesis, depending on the dose and generation.