Effect of sub-lethal concentration of thiamethoxam on Tetranychus urticae Koch: an age stage two sex life table approach
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عنوان دوره: سومین کنگره بین المللی حشره شناسی ایران
نویسندگان
1Department of Entomology and Plant Pathology, Aburaihan Campus, University of Tehran, Pakdasht, Iran,
2Department of Entomology and Plant Pathology, Aburaihan Campus, University of Tehran, Pakdasht, Iran, reza.havasi@ut.ac.ir, kkheradmand@ut.ac.ir
3Pesticides Research Department, Iranian Research Institute of Plant Protection, AREEO, Tehran, Iran
4Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran,
چکیده
Two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most important pests on a wide range of crops in greenhouses and orchards worldwide. Control of T. urticae has been largely based on using acaricides. Unfortunately, frequent application of insecticides against this pest has caused many problems including resistance to insecticides. Therefore, investigation on the effects of pesticides with a novel mode of action against this pest is necessary. The present study aimed to assess the sublethal effect of thiamethoxam (Actara®) in three concentrations (LC5, LC10 and LC20) on life table parameters of T. urticae. The lethal and sub-lethal concentrations were calculated using bioassay experiments and leaf-dipping method. The primary population of the TSSM was collected from infested plants in the greenhouse of the Pakdasht (Tehran, Iran) and after identification, was reared on green bean plants. The experiment was performed in a growth chamber at 25±2 ºC, 60±5% RH, and 16:8 h (L:D). The raw life history data was analyzed according to the age-stage, two-sex life table method. Results revealed that female longevity significantly reduced with increasing sub-lethal concentrations compared to that in control (ranged between13.01 to 10.31 days). The total mean number of eggs increased from 45.89 eggs / female (LC20) to 61.1eggs / female (control). In contrast, the reproduction parameters of TSSM including APOP and TPOP were not significantly different among all concentrations. The intrinsic rate of increase (r) was 0.2348, 0.2326, 0.2308 and 0.2340 day-1 in LC5, LC10 and LC20 treated groups and control, respectively. The net reproduction rate (R0) treatments of was obtained as 48.59, 41.89 and 36.71offspring/individual in LC5, LC10 and LC20, respectively, which showed a significant decrease in comparison with the control (48.88 offspring/individual). The gross reproduction rate (GRR) of all chemical treatments (LC5 = 55.01, LC10 = 46.06 and LC20 = 41.52 offspring/individual) and control (54.01 offspring/individual) without significant difference. Finally, the finite rates of population growth (λ) in three concentrations were not significantly different. Moreover, mean generation time (T) in the control and LC5, LC10 and LC20 treatments were 16.61± 0.08, 16.53±0.09, 16.05±0.09 and 15.60±0.07 days, respectively. In comparison to control, sublethal concentrations of thiamethoxam was harmful to the survival, longevity, and fecundity of T. urticae and could be further developed for use in integrated pest management of the TSSM in greenhouse production systems.
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