Susceptibility of Different Egyptian Populations of Tuta absoluta (Meyrick) to Selected Insecticides and Associated Detoxification Enzyme Activities

The tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a highly destructive invasive pest of tomato, and its ability to develop resistance to insecticides is well known. The susceptibility of three field populations from Egypt (Luxor, Assuit, and Giza) to the insecticides chlorantraniliprole, chlorfenapyr, indoxacarb, emamectin benzoate, and spinetoram was evaluated by leaf-dip bioassays. The second-instar larvae were exposed, and mortality was noted 24, 48, and 72 h later. Probit analysis was used to calculate lethal concentrations (LC50 and LC90) and resistance ratios (RR50). Furthermore, key detoxification enzymes (α-esterases, cytochrome P450 monooxygenases, and glutathione S-transferases) were also measured to identify possible metabolic resistance mechanisms. Considerable inter-population differences were observed. Detoxification enzymes (α-esterases, cytochrome P450 monooxygenases, and glutathione S-transferases) were measured. The Luxor population showed the highest LC50 values and resistance ratios, especially to chlorfenapyr and indoxacarb, suggesting low-to-moderate resistance, while the Giza population was the most susceptible. Emamectin benzoate and spinetoram provided excellent control of all laboratory and field strains.