Aboutalebian Soureshjani, A., Rafiee-Dastjerdi, H., Khajehali, J., Naseri, B., & Hassanpour, M. (2023). Sensitivity of different populations of the tomato leaf miner Tuta absoluta (Lep: Gelechiidae) to thiocyclam hydrogen oxalate and the effect of three s

Abstract

1. Introduction: The tomato leaf miner Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the major pests of tomato (Solanum lycopersicum L.) production worldwide. Insecticide use has always been the main strategy to control this pest. The overuse of insecticides has resulted in the development of high resistance to several insecticides. Thiocyclam hydrogen oxalate is one of the recommended insecticides for this pest. This insecticide is a nereistoxin that inhibits the ion channel of the nicotinic acetylcholine receptor (nAChR). A study of resistance to this insecticide and the mechanism of resistance in Iran may lead to appropriate tactics for resistance management in the control of T. absoluta. Therefore, in this study, the sensitivity of this pest to the insecticide thiocyclam and the effect of synergists to increase its sensitivity was investigated.
2. Material and Methods: The population of T. absoluta was collected from different greenhouses in Iran. The population with the lowest LC50 was selected as the sensitive population for the bioassay experiments. The insects were collected in 2020 and tested in the laboratory of Mohaghegh Ardabili. The insecticidal efficacy of thiocyclam hydrogen oxalate alone and in combination with piperonyl butoxide PBO (monooxygenase inhibitors), diethyl maleate DEM (inhibitor of glutathione S-transferase) and triphenyl phosphate TPP (carboxylesterase inhibitors) was evaluated. For experiments with synergists, concentrations of 1000 ppm for TPP and 200 ppm for DEM and PBO were prepared. The bioassay was performed with second instar larvae, with leaves immersed for ten seconds. Laboratory conditions were 25±1°C, 60% RH, and 16:8 hours of light. A total of eight populations from Iranian greenhouses were studied with five replicates, five concentrations and ten insects per replicate. Larvae were exposed to the synergists for 2 hours before being used for the bioassay test.
3. Results and Discussion: Based on the bioassay of the insecticide thiocyclam hydrogen oxalate on different populations of T. absoluta in the second larval instar, different levels of susceptibility can be observed between populations, and the resistance ratio in T. absoluta populations of Ardabil1, Yasouj, Borujen, Yazd, Bushkan, Kerman, Esfahan and Ardabil2 was 3.65, 2.70, 3.05, 1.71, 1.63 and 1.062 fold, respectively. The population in Ardabil1 was the most resistant population with a 3.65-fold resistance ratio and an LC50 value of 275.12 mg/L. The population in Yasouj was the most sensitive population with an LC50 value of 82.75 mg/L. Synergistic effects on resistant and sensitive populations to thiocyclam hydrogen oxalate insecticides showed that the synergists of piperonyl butoxide had the greatest reduction in LC50 in different populations of T. absoluta. In addition, the population in Ardabil had the highest resistance ratio, with the synergistic effects of piperonyl butoxide, diethyl maleate, and triphenyl phosphate on the tomato leaf miner being 1.95, 1.83, and 1.76-fold, respectively. The highest rate of synergists in the Yazd and Ardabil populations was related to the PBO synergist, which reduced the LC50 from 252.27 and 275.12 mg/L (without insecticide) to 102.15 and 141.18 mg/L (larvae were exposed to the synergist), in the Yasouj population, the synergist ratio was slightly reduced for PBO, but for the DEM and TPP, the synergist ratio was not reduced or very low. The results show that the use of the insecticide thiocyclam hydrogen oxalate with the synergists piperonyl butoxide, diethyl maleate, and triphenyl phosphate increased the toxicity and decreased the resistance of thiocyclam hydrogen oxalate.
4. Conclusion: In general, the results seem to indicate that thiocyclam hydrogen oxalate is still effective against tomato leaf miner loss, and that resistance levels are not critical. Synergists can be used to delay low resistance, reduce spray pressure for this insecticide, and use alternative insecticides. The results of this research will be useful for managing resistance of tomato leaf miner moths to this insecticide.

Journal of Vegetables Sciences.