Effects of diallyl sulfide and diallyl disulfide on the antioxidant system and energy allocation of Tomato leafminer larvae, Tuta absoluta Meyrick

Tuta absoluta Meyrick (Lep.: Gelechidae) has recently caused significant damages to tomato production in greenhouses and fields, necessitating sustainable and efficient management. Garlic has antimicrobial and antioxidant properties due to the presence of various compounds such as mono, di, and trisulfides. Meanwhile, diallyl sulfide and diallyl disulfide have demonstrated effective insecticidal activity against various insects. Due to their rapid decomposition and almost specific lethality, natural compounds may be a viable alternative to chemical compounds in the control of tomato leafminer. The purpose of this study was to determine the effect of diallyl sulfide and diallyl disulfide LC30 and LC50 concentrations on the antioxidant system and energy allocation of tomato leafminer.

The leaf disc method was used to conduct the larval bioassay. Initially, preliminary testing was performed to determine the final concentrations of 0.0625, 0.125, 0.5, 1, and 2%. Each leaf was submerged in the toxic solution for ten seconds before being transferred to 8 cm Petri dishes. Then, second instar larvae (seven to ten days old) were placed on the leaves and allowed to feed on both control and treated leaves. After 24 hours, larval mortality was counted, and POLO-Plus software was used to calculate lethal concentrations. The second instar larvae were initially immersed separately at LC30 and LC50 concentrations of each component to evaluate the antioxidant system and energy allocation. The control larvae were fed only solvent and each treatment used 60-second instar larva separately. After 24 hours, the treated and control larvae were divided into three groups of 10, and each group was homogenized in distilled water. Samples were centrifuged at 20,000 ×g at 4 ° C for 20 min, and supernatants were used to determine the activity of catalase, superoxide dismutase, peroxidase, glucose-6-phosphate dehydrogenase, and malondialdehyde concentration, as well as energy consumption.

Catalase activity was significantly higher in treated larvae than in control larvae, with the highest activity observed following LC50 treatment with diallyl disulfide. Except for the concentration of diallyl sulfide LC30, the treated larvae had increased peroxidase activity compared to the control. The diallyl disulfide LC50 concentration demonstrated the highest activity. Although larvae treated with diallyl disulfide at the LC50 concentration had the highest superoxide dismutase activity, there was no significant difference in the LC30 concentrations of the two compounds compared to control larvae. The highest glucose-6-phosphate dehydrogenase activity was observed in larvae treated with both compounds at LC50 concentrations; however, the lowest was observed in larvae treated with both components at LC30 concentrations. Finally, the malondialdehyde concentration was significantly higher in the treated larvae than in the control larvae. The amount of energy allocated to tomato leafminer treated with diallyl sulfide and diallyl disulfide was significantly lower than the control. Finally, the lowest value was observed in larvae treated with diallyl disulfide at its LC50 concentration, but there was no significant difference between the other treatments.

The two compounds, diallyl disulfide and diallyl sulfide, increased the antioxidant enzyme activities in tomato leafminer larvae through fat peroxidation and oxidative stress. In treated larvae, the amount of energy required for metabolic activity increased while the amount of energy available to the body decreased significantly. As a result, it is concluded that these two ingredients, garlic essential oil and tomato leafminer mortality, would effectively cause physiological disturbances, most notably in the antioxidant system and energy allocation. Based on the findings, field experiments are necessary to determine the environmental toxicity of these compounds and their importance in reducing crop damage compared to control. Additionally, the efficacy and combination of these compounds can be compared to other field control methods that aim to maintain a healthy crop with minimal pest damage.