Determination of acequinocyl resistance and resistance mechanisms in various Tetranychus urticae koch (Acari: Tetranychidae)

The two-spotted spider mite, Tetranychus urticae Koch, is a common agricultural pest often controlled through acaricide applications. However, resistance development poses challenges to chemical control efficacy. Resistance status and resistance mechanisms should be known in order to manage acaricide resistance. To determine the current resistance status and elucidate the molecular mechanisms underlying resistance, 10 T. urticae populations collected from Antalya, Mersin, and Ankara provinces in Turkey between 2021 and 2023 were tested for their susceptibility to acequinocyl, a registered acaricide for over a decade in the country. The results showed that two populations were resistant to acequinocyl (Tu4= 153-fold, Tu8= 257-fold), while eight populations remained sensitive. Similar resistance patterns were observed for bifenazate having same mode of action (Tu4= 1330-fold, Tu8= 690-fold). In the highly resistant populations, a M128T mutation in the conserved cd-1 helix of the cytochrome b gene, the target site for acequinocyl, was identified, however, the role of the mutation needs to be validated. Experiments with synergistic compounds suggested potential associations of detoxification enzymes with acequinocyl resistance. A transcriptomic analysis was conducted to unveil the role of detoxification enzymes at the gene level, and the differentially expressed genes were subsequently analyzed. The results obtained in the present study will contribute to design proper acaricides resistance management programs.