Gizem Berber-Tortop, Hilal Şule Tosun, Cengiz Ikten, Sibel Yorulmaz
Tetranychus urticae, a polyphagous species, is one of the major pests of apple orchards. Although chemical control remains a preferred management strategy due to its convenience and rapid efficacy, T. urticae has developed resistance to numerous acaricides. In this study, pyridaben LC (lethal concentration) values, resistance ratios, detoxification enzyme activities, synergism tests, the H92R target-site mutation were investigated in T. urticae populations collected from apple orchards. Pyridaben susceptibility levels of T. urticae populations collected in the summer of 2023 ranged from 1.5 to 14.8 folds compared to the LC50 (LC of 50% individuals) values of the susceptible population. Synergism tests showed that PBO, a P450 inhibitor, increased pyridaben toxicity. Cytochrome P450 monooxygenase enzyme activities determined using a microplate reader varied between 0.0037 and 0.0072 mOD/min/mg protein. Among the collected populations, the H92R mutation was detected only in the GO population. In addition, 13 cycles of selection applied to a hybrid population, created by combining T. urticae populations collected in the summer of 2024, resulted in a 46-fold resistance increase, accompanied by a rise in H92R mutation frequency from 27% to fixation (100%). These findings provide important insights into the biochemical and molecular mechanisms underlying pyridaben resistance and the genetic basis of resistance evolution in T. urticae. The results contribute to the development of more sustainable and effective pest management strategies in apple orchards.