Study on the variations in acaricide sensitivity between two spider mite species, Amphitetranychus viennensis and Tetranychus urticae, in Chinese orchards

Amphitetranychus viennensis and Tetranychus urticae, are destructive agricultural and horticultural pests. Their management primarily relies on acaricides; however, little is known about the susceptibility of these two species to these chemicals. The current study assessed the susceptibility of A. viennensis and T. urticae to ten acaricides, investigated the detoxification enzyme activities, and conducted transcriptional analyses after bifenazate and cyetpyrafen exposure. The results showed that the LC₅₀ values of most acaricides against T. urticae were notably higher than those for A. viennensis at different developmental stages. At the adult stage, A. viennensis was more tolerant to bifenazate than T. urticae, while A. viennensis showed increased sensitivity to cyetpyrafen than T. urticae. After cyetpyrafen exposure, glutathione S-transferases (GSTs) activity in T. urticae were markedly higher at 6 and 12 h, whereas that in A. viennensis increased only at 6 h. No notable differences in cytochrome P450 monooxygenases (P450s) levels were found in T. urticae between the control and treatment groups (cyetpyrafen or bifenazate). However, A. viennensis treated with either cyetpyrafen or bifenazate showed a marked decrease in P450 levels at 12 h. Furthermore, more detoxification genes in both species were activated in response to bifenazate or cyetpyrafen. Differential metabolic detoxification mediated by P450 and GST genes may primarily account for the distinct responses of these species to bifenazate and cyetpyrafen. These findings reveal the distinct detoxification capacities of the two species in response to acaricides and highlight the importance of applying species-specific management strategies for these pests.