Tetranychus urticae (Acari: Tetranychidae) is one of the most important pests of agricultural crops with worldwide distribution causing considerable damage to different products. Application of chemical acaricides is one of the most important strategies used for the control of this pest. Entomopathogenic fungi, however, have been proposed as alternative control agents. In this study, sub-lethal effects (LC10 = 6.76 × 102, LC20 = 8.74 × 103, and LC30 = 55.38 × 103 conidia ml−1) of Beauveria bassiana strain TV on the life table parameters of T. urticae were evaluated under laboratory conditions. The results demonstrated that by increasing the concentration, a significant decline was observed in adult longevity of both male and female individuals. Total fecundity of T. urticae was calculated as 45.16, 36.28, 23.98, and 18.21 eggs in control, LC10, LC20, and LC30 treatments, respectively. Sub-lethal concentrations drastically affected the population parameters of this mite pest. The intrinsic rate of increase (r) ranged from 0.1983 to 0.1688 day−1 for the mites treated with distilled water and LC20 treatments, respectively. The net reproductive rate (R0) was affected by the sub-lethal concentrations (lower value at LC30 concentration: 11.19 offspring/individual). Considering the detrimental effects of B. bassiana on some biological parameters of T. urticae, it can be concluded that this product can be used to develop targeted interventions aimed at integrated pest management of this pest.
Two-spotted spider mite, Tetranychus urticae Koch, is a cosmopolitan pest causing economic damage to a wide range of different host plants worldwide. In the present study, bottom-up effects of four common greenhouse plants including cucumber (cultivar “Negin”), tomato (cultivar “Isabella”), eggplant (cultivar “Bell”) and watermelon (cultivar “Crimson”) on biological parameters of this pest were evaluated using age-stage, two-sex life table theory. The obtained results revealed that the durations of different life stages of T. urticae were significantly affected by the host plants tested. Accordingly, the highest and lowest recorded values for duration of total immature stages of this mite were recorded on tomato (12.09 ± 0.25 day) and eggplant (8.37 ± 0.16 day), respectively. The duration of oviposition period was also significantly different and the highest value was estimated on watermelon (14.19 ± 1.26 day). Furthermore, host plants tested significantly affected the mortality of different life stages and the highest immature mortality was estimated on tomato (65.31 ± 4.81 %). The highest and lowest estimated values for intrinsic rate of increase (r) were recorded on cucumber (0.239 ± 0.014 day-1) and tomato (0.104 ± 0.016 day-1), respectively. The calculated values for mean generation time (T) were the highest on tomato (17.81 ± 0.53 day) and the lowest on eggplant (13.98 ± 0.28 day). These findings demonstrated that cucumber and tomato had the lowest and highest negative effects on the biological parameters of T. urticae, respectively.
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