Sublethal effects of chlorfenapyr on biological parameters of Tetranychus urticae (Acari: Tetranychidae) and predatory mites Phytoseiulus persimilis and Neoseiulus californicus (Acari: Phytoseiidae)

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), poses a significant threat to agricultural production due to its herbivorous feeding habits and pesticide resistance. This study investigated the effects of sublethal concentrations of chlorfenapyr (LC10, LC20 and LC30) on the development and reproduction of T. urticae and its predatory mites Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus McGregor (Acari: Phytoseiidae) under controlled laboratory conditions. Bioassay tests were conducted using a leaf disk dipping method at various pesticide concentrations. The raw data from the life table experiments were analyzed based on age-stage, two-sex life table analysis at a 5% significance level. Our findings revealed significantly reduced T. urticae egg hatching time at LC20. The duration of larva and protonymph stages of predatory mites often increased from LC20 onwards, while the deutonymph stage showed no significant changes. The total lifespan of T. urticae decreased from 23.11 days (control) to 18.65 days (LC30) and in both predators, it significantly reduced from LC20. The fecundity, GRR and R0 declined significantly at LC10 and above for all species, and the mean generation time (T) showed a significant reduction only in T. urticae. The results suggest that chlorfenapyr displays high toxicity against T. urticae, potentially enabling effective control at low concentrations, while having minimal impact on N. californicus at field-relevant concentrations, as significant effects were observed at higher doses, and exhibiting moderately toxic to P. persimilis, demonstrating its selective toxicity and making it a viable option for IPM programs when applied at appropriate concentrations to minimize risks to beneficial predatory mites.