Biochemical changes associated with foliar application of some compounds for controlling <i>Tuta absoluta</i> (Lepidoptera: Gelechiidae) on tomato plants under greenhouse and field conditions

Solanaceous plants are of great economic importance in Egypt, with crops like potatoes, tomatoes and eggplants playing vital roles in the agricultural sector. The emergence of the invasive pest Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) presents a major challenge to tomato cultivation. During the 2024 season, the effectiveness of various compounds against T. absoluta larvae on tomato plants in greenhouse and open field was tested. The highest reductions in insect populations were observed with emamectin benzoate. Following this, other insecticides like metaflumizone, thiocyclan hydrogen oxalate and indoxacarb also showed significant efficacy in reducing T. absoluta. On the other hand, Bacillus thuringiensis showed the most effective reductions in insect populations. Interestingly, in the study, there were no significant differences observed between the tested compounds except for a notable distinction between B. thuringiensis and emamectin benzoate (p ≤ 0.05). Significant variations in chlorophyll content were observed based on the application of different compounds. Particularly, treatments involving thiocyclan hydrogen oxalate and B. thuringiensis resulted in a notable increase in chlorophyll levels. In contrast, the application of emamectin benzoate, indoxacarb and the control showed the lowest chlorophyll content levels. Over a 10-day period some of these compounds led to a significant decrease in nonenzymatic components in tomato plants compared to the control. Particularly noteworthy were the significant reductions observed in all non-enzymatic components in leaves treated with thiocyclan hydrogen oxalate. All the compounds tested had an impact on antioxidant enzymes with significant variations observed among the different treatments. Specifically, the application of emamectin benzoate resulted in an increase in enzymatic activity particularly in catalase, peroxidase and superoxide dismutase, notably 10 days after application. The application of thiocyclan hydrogen on tomato plants resulted in a decrease in the activities of antioxidant enzymes. Furthermore, both B. thuringiensis and cyromazine impacted the activity of the peroxidase enzyme, with significant differences noted between them. Overall, there were significant variations in the activities of all antioxidant enzymes among the different treatments (p ≤ 0.05).