Unveiling multi‐pesticide resistance and RNAi effectiveness in field populations of Tetranychus urticae (Koch)

BACKGROUND: The two-spotted spider mite, Tetranychus urticae, is a significant agricultural pest causing substantial economic losses annually, which primarily relies on chemical control. RESULTS: The current study characterizes the resistance levels of field populations of T. urticae across China against different acaricides (fenpropathrin, abamectin, pyridaben, bifenazate and etoxazole), with some populations showing severe resistance against all tested acaricides. The mutation frequencies of target genes via fast amplicon sequencing indicate their close relationship with the resistance levels, but only certain haplotypes of resistant genes could precisely indicate the resistance level. Besides, RNA interference (RNAi) silencing of well-recognized targets including VGSC (voltage-gated sodium channel) and GABA-Cl (γ-aminobutyric acid-gated chloride channel) receptor turned out to be effective in a laboratory population but completely ineffective in field populations. CONCLUSION: Field populations have developed high-level resistance. Certain haplotypes could be developed as a precision molecular marker for resistance diagnosis. The difference in RNAi silencing in a susceptible population and field resistant populations is worth exploring further in the future. © 2025 Society of Chemical Industry.