Resistance monitoring, sublethal and transgenerational effects of different acaricides on the European red mite, Panonychus ulmi (Koch).

Background

Panonychus ulmi (Koch) is an important phytophagous mite pest in apple orchards, and acaricide resistance increasingly compromises its control. Sublethal acaricide exposure may further affect reproduction and population dynamics. This study surveyed resistance to six acaricides in 15 field populations from Xinjiang, China, during 2024-2025 and assessed the LC20-induced sublethal and transgenerational effects of pyridaben, bifenazate and bifenthrin in susceptible and resistant populations.

Results

Resistance monitoring showed clear regional differences in susceptibility to the six acaricides. The WS_TF population showed high resistance to bifenthrin (47.19-fold), while AKS_YGQ_YK and WS_TF exhibited low-to-moderate resistance to bifenazate (35.98- and 23.19-fold), pyridaben (28.01- and 3.33-fold) and cyflumetofen (13.29- and 26.25-fold), respectively. Most populations remained susceptible to abamectin and cyetpyrafen. Exposure to LC20 of pyridaben, bifenazate and bifenthrin reduced fecundity in parental generation of the susceptible population (Lab_SS), whereas only pyridaben reduced fecundity in WS_TF. Life-table analysis revealed resistance-dependent transgenerational responses. In Lab_SS, LC20 exposure generally suppressed reproduction and population growth in the F1 and F2 generations, whereas hormesis occurred in WS_TF, particularly following bifenthrin exposure.

Conclusion

Resistance monitoring showed clear regional variation in acaricide susceptibility among P. ulmi populations. Sublethal and transgenerational effects depended on both acaricide and resistance background. Integrating resistance status with these population-level effects may improve acaricide selection and rotation and reduce the risk of pest resurgence. © 2026 Society of Chemical Industry.