Whiteflies are major pests of many agricultural crops around the world. They belong to the Aleyrodidae family of the Hemiptera order. Cotton whitefly, Bemisia tabaci and greenhouse whitefly Trialeurodes vaporariorum are among the most damaging species among whiteflies. Neonicotinoids are common insecticides that target the nicotinic acetylcholine receptors of insects. The detoxification mechanism by cytochrome P450 has been reported as a key factor in the resistance of insect species to neonicotinoids. In this research, six populations of B. tabaci and five populations of T. vaporariorum were collected from different regions of Isfahan province. All six whitefly populations belonged to biotype B. The sensitivity of populations to thiamethoxam insecticide was eva‎luated by bioassay by leaf dip bioassay method. The LC50 value of thiamethoxam insecticide for populations B. tabaci, from 28.36 (University) to 359.05 (Qahdarijan) milligrams of effective substance per liter (mg a.i.L−1) and for populations T. vaporariorum was calculated from 5.03 (Shahr Abrisham) to 76.24 (Mobarakeh) mg a.i.L−1 compared to thiamethoxam insecticide. In the population of Qahdarijan, B. tabaci had a resistance ratio of 12.66 times, and in Mobarakeh, T. vaporariorum had a resistance ratio of 15.15 times. To detect resistance mechanisms, the effects of pretreatment with three synergists, piperonyl butoxide (PBO), diethyl maleate (DEM) and triphenyl phosphate (TPP), were investigated. Piperonyl butoxide, as an inhibitor of cytochrome P450 monooxygenases, increased the toxicity of thiamethoxam by 7.15 times in Qahdarijan population and 6.28 times in Mobarakeh population. To provide further evidence for the role of detoxification enzymes in thiamethoxam resistance, the activities of P450 monooxygenases, carboxylesterases and glutathione S-transferases were measured in cotton whitefly and greenhouse whitefly populations. Compared to the sensitive population, the activity of P450 monooxygenases increased more than twice in the populations of Qahdarijan and Mobarakeh, but no significant difference was observed for the activity of carboxylesterases and glutathione S-transferases between the populations. Cross resistance in these populations against imidacloprid and acetamiprid was eva‎luated. Both species of cotton whitefly and greenhouse whitefly showed high cross resistance to these two insecticides. It seems that the increase in detoxification, especially the high activity of cytochrome P450 monooxygenase enzymes, is the main mechanism of resistance to neonicotinoid insecticides in cotton whitefly and greenhouse Whitefly populations. Management of insecticide resistance requires consideration during the development, commercialization, and use of any new compound. Monitoring the relative sensitivity of field populations to new and previously introduced insecticides is important to enable effective, optimal use and management of insecticide resistance. To manage resistance to neonicotinoid insecticides, we need to know the mechanisms of resistance in field populations and determine their effect on the sensitivity of laboratory and field populations.

جهانگير خواجه علي , نفيسه پورجواد

مجيد طالبي

حسن كريم مجني , لادن طلايي