Characterisation of pyridaben resistance in Tetranychus urticae in the Mediterranean basin

Tetranychus urticae , the Two-Spotted Spider Mite (TSSM) is a plant pest causing serious economic damage in various crops worldwide. The main means of controlling TSSM in the field are based on chemical pesticides but cases of reported resistance are numerous. Pyridaben is one of the pesticides used against TSSM, however reports from growers in the area indicated that it is losing its efficiency. In this study, we performed a survey testing field populations for their susceptibility to pyridaben over the years 2023-2025. We then randomly selected five populations of TSSM from this survey originating from different geographic locations and with variable resistance abilities to pyridaben. We tested these populations both for cytochrome P450-based metabolic breakdown of pyridaben and for target-site mutations. Our survey showed that pyridaben resistance is highly common in the field with 32 populations of 37 tested being resistant to a dose of pyridaben which is double the recommended dose for commercial use in the field. Furthermore, we show that resistance in most populations is likely to be metabolic, and we use a P450-inhibitor to successfully re-introduce susceptibility to three of four resistance populations. Our data sheds light on the current situation of TSSM resistance to pyridaben in the Mediterranean basin and strongly supports reduction in use of this compound in the near future. • Survey of >35 field populations of TSSM uncovered wide spread resistance to pyridaben. • Only one population was found to have a known target site mutation. This was also the population with the highest resistance abilities. • Synergist test indicated that most field populations have a metabolic-based resistance, based on cytochrome P450 enzyme family.