Status and mechanism of insecticide resistance of Ceratitis capitata (Diptera: Tephritidae) populations in East Mediterranean Region in Türkiye

Abstract C eratitis capitata Wied. (Diptera: Tephritidae), a major pest of citrus, stone fruit, and subtropical plants, represents significant economic threats. This study evaluated the resistance levels of eight C. capitata populations from the East Mediterranean region of Türkiye to esfenvalerate, spinosad, tau-fluvalinate, and malathion using bioassays, biochemical analyses, and molecular techniques. The activities of Esterase, Glutathione S-transferase (GST), and Monooxygenase were quantified, along with the expression of eleven CYP4, CYP6, CYP9, and CYP12 genes. A grower survey indicated that 70% of respondents predominantly rely on pyrethroid insecticides. Resistance factors (RF), based on LC 50 values of field populations relative to a susceptible strain, ranged from 10.16 to 23.80 for esfenvalerate, 2.75 to 7.54 for malathion, 1.93 to 3.31 for spinosad, and 3.02 to 12.40 for tau-fluvalinate. Strong correlations were detected between monooxygenase activity and esfenvalerate resistance, as well as between GST activity and pyrethroid resistance. Biochemical assays revealed that the Çağlarca population exhibited the highest Esterase, GST, and Monooxygenase activity, while Dalakderesi also showed notably elevated levels of all three enzymes, indicating a strong association between enzymatic detoxification and resistance levels. Residue trials demonstrated that spinosad exhibited the highest initial adult mortality within 24 h, whereas tau-fluvalinate had the lowest efficacy. By the 10th day, all insecticides had lost effectiveness, except spinosad, which significantly reduced larval emergence. Gene expression analyses revealed upregulation of CYP6A51-2, implicating its role in pyrethroid resistance. These findings indicate low to moderate levels of insecticide resistance in C. capitata populations, emphasizing the necessity for integrated resistance management strategies, such as rotating insecticides with different modes of action, to sustain effective control.