The cotton whitefly (Bemisia tabaci) and the greenhouse whitefly (Trialeurodes vaporariorum), are among the most damaging agricultural pests. Pyrethroids are synthetic analogs of natural pyrethrins that primarily act on sodium channels in nerve cells, causing prolonged channel opening, ultimately leading to paralysis and insect death. Resistance to pyrethroids in arthropod is often linked to mutations in the sodium channel gene and increased activity of detoxifying enzymes including, cytochromeP450 monooxygenases, carboxylesterases, and glutathione S-transferases. The aim of this study was to assess resistance to the pyrethroid insecticide cypermethrin and elucidate its underlying mechanisms in Iranian populations of B. tabaci and T. vaporariorum. Five populations of B. tabaci and eight populations of T. vaporariorum were collected from different regions of Isfahan and Yazd provinces. Susceptibility to cypermethrin was determined using leaf-dip bioassays. The LC₅₀ values for T. vaporariorum populations ranged from 427.64 mg a.i./L (University) to 2586.50 mg a.i./L (Yazdabad), while those for B. tabaci populations ranged from 154.12 mg a.i./L (Gaz) to 3938.60 mg a.i./L (Dehaghan). The resistant population of Yazdabad exhibited a 6-fold resistance ratio, whereas the resistant population of Dehaghan showed a 25-fold resistance ratio compared to susceptible populations. To determine metabolic resistance mechanisms, the effects of pre-treatment with three synergists—piperonyl butoxide (PBO), diethyl maleate (DEM), and triphenyl phosphate (TPP)—were eva‎luated. Synergistic ratios for susceptible and resistant populations were as follows: Gaz: 1.04, 1.24, and 1.17; Dehaghan: 4.90, 2.18, and 1.03; University: 1.2, 1.42, and 1.14; Yazdabad: 1.23, 1.17, and 3.21. These results underscore the significant role of carboxylesterases and glutathione Stransferases in cypermethrin detoxification. Furthermore, enzyme activity measurements showed elevated glutathione S-transferase activityin the resistant Dehaghan population and and increased carboxylesterase activity in the resistant Yazdabad population. Cross-resistance studies revealed that the cypermethrin-resistant Dehaghan population exhibited high cross-resistance to permethrin, while the Yazdabad-resistant population showed high cross-resistance to both permethrin and spirotetramat. In conclusion, increased metabolic detoxification— particularly via the overexpression of glutathione S-transferase and carboxylesterase genes, are key factors in cypermethrin resistance in B. tabaci and T. vaporariorum. These findings may facilitate early detection of cypermethrin resistance in whitefly populations and contribute to more effective insecticide m

جهانگير خواجه علي , نفيسه پورجواد

لادن طلايي , حسن كريم مجني