Monitoring acaricide resistance and the frequency of associated target-site mutations in Tetranychus urticae populations from rose glasshouses in China.

Background: The two-spotted spider mite, Tetranychus urticae, is a serious pest of glasshouse roses. The rapid development of resistance to acaricides has severely impacted rose production. To investigate the resistance status of T. urticae in glasshouse rose cultivation in China, we tested the susceptibility of 10 populations to 12 commonly used acaricides and examined the frequency of target-site mutations associated with acaricide resistance.

Results: All of the tested populations showed resistance to at least eight types of acaricides and exhibited high levels of resistance to abamectin, diafenthiuron, hexythiazox and spirodiclofen. The JN-YN and LZ-GS populations even developed >70 000-fold resistance to abamectin. Additionally, resistance to the newly applied bifenazate or cyetpyrafen was detected in eight populations. Many glasshouse-collected populations showed significantly increased activity of detoxifying enzymes and harbored high frequencies of target-site mutations known to be associated with resistance. A newly discovered I136A mutation in cytb was detected at >85% frequencies in two populations with high levels of bifenazate resistance, and its frequency showed a strong correlation with the median lethal concentration values in all of the populations.

Conclusions: Multiple-acaricide resistance exists extensively in all collected populations. The high resistance levels of collected populations to many acaricides, together with multiple target-site mutations, indicate a serious resistance status of T. urticae in rose glasshouses in China. The role of the newly discovered I136A mutation in bifenazate resistance requires further verification. These results will be essential for implementing a well-thought-out resistance management program for rose cultivation in China. © 2024 Society of Chemical Industry.