Imidacloprid Resistance Status and Role of Detoxification Enzymes in Bemisia tabaci (Hemiptera: Aleyrodidae) Populations from Iran

Neonicotinoid pesticides such as imidacloprid and thiacloprid are agonists of nicotinic Acetylcholine Receptors (nAChRs). This chemical group is commonly used in controlling sucking pests such as cotton whitefly, B. tabaci, one of the most serious and destructive pests of agricultural crops worldwide. Bioassays were performed using a leaf dip method and Ahvaz population with the lowest LC50 value (24.40 mg ai L-1) was considered as the susceptible population. LC50 values of Karaj, Isfahan, Kashan, Gorgan and Minab populations were estimated as 189.81, 136.91, 106.95, 141.09, and 68.31 mg ai L-1, respectively. Low Resistance Ratios (RR) to imidacloprid were observed in the tested populations (RR values< 10). The piperonylbutoxide (PBO) and TriPhenyl Phosphate (TPP) showed the highest synergistic ratios of 1.99 and 2.42 in the population of Kashan, respectively, but DiEthyl Maleate (DEM) did not show a high synergistic ratio. The activity of cytochrome P450-dependent monooxygenase (P450s), CarboxylEsterase (CarEs) and Dlutathione S-Transferases (GST) were measured. There was an increase in the activity of P450s up to 3-fold in the Gorgan population and CarE activity in Kashan population up to 2-fold in comparison to the susceptible population. Based on the results, P450s and CarEs are possibly the enzyme systems responsible for imidacloprid resistance in the tested populations of B. tabaci.