Sub-lethal effects of Spiromesifen on population growth parameters of Tetranychus urticae (Acari: Tetranychidae)
عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
نویسندگان
چکیده
Two-spotted spider mite is one of the most important pests of the greenhouses, farms and orchards in different regions of the world. Control of this pest is mainly based on the use of chemical acaricides. In this study, cucumber (Cucumis sativus L.) was selected as the host plant. Sub-lethal effects of Spiromesifen (Oberon®,SC 24%) with three concentrations 92, 171 and 266 ppm (LC10, LC20 and LC30) and control (distilled water) on the population growth parameters of this pest were evaluated at laboratory conditions with 25 ± 2 oC, 65 ± 5% RH and a photoperiod of 16 L : 8 D. The concentrations were sprayed on the leaf disc. In each concentration, 100 protonymphs were treated. Data were analyzed based on the Age-Stage Two-Sex Life Table theory. The results showed that sub-lethal concentrations of Spiromesifen significantly affected the fecundity and duration of different life stages of two-spotted spider mite in the first generation. Developmental time was significantly different among the treatments and control and ranged from 2.222 to 3.9432 (days). Male longevity significantly reduced with increasing sub-lethal concentrations compared to control. Duration of female longevity and their fecundity were both significantly reduced by the treatments of Spiromesifen. The mean number of eggs was increased from 9.150 (LC30) to 37.167 (control). In the second generation, the minimum developmental time was recorded for LC30 had significant different to the control. However, male mortality was not significantly different among different treatments and control, but female mortality was different. The highest and lowest values of the intrinsic rate of increase (r) were recorded in control (0.1762 day-1) and LC30 (0.0946 day-1), respectively. The value of this parameter in LC10 and LC20 was calculated 0.1247 and 0.1293 (day-1), respectively. Finite rates of population increase (λ) varied from 1.0977 (day-1) in LC30 to 1.1926 (day-1) in control. Mean generation time (T) was not varied among control and different treatments. The net reproductive rate (R0) decreased with increasing concentrations from 28.6129 (female offspring) in control to 6.1739 (female offspring) in LC30. The highest and lowest calculated values for pre-adult mortality were recorded in LC30 (0.4347 ± 0.0515%) and control (0.2903 ± 0.0457%), respectively. Our results indicated that increasing concentrations of Spiromesifen had significant negative effects on population growth parameters and fecundity of T. urticae, so Spiromesifen can be applied as an appropriate acaricide to control this pest.
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