A combination of pesticides and biological control agents is frequently necessary to achieve successful pest management requiring the assessment of their compatibility for the intended purpose. Aphidius flaviventris Kurdjumov is one of the parasitoids of the cotton aphid Aphis gossypii Glover, whose susceptibility to pesticides was not yet investigated. Accordingly, we investigated the lethal and sublethal effects of the commonly utilized insecticide mixture thiacloprid + deltamethrin on the cotton aphid and its parasitoid wasp Aphidius flaviventris. The estimated LC50 for the aphid was 14.1 mg ai/l; the effects of sublethal exposure at LC10 (2.80 mg ai/l) and LC30 (7.28 mg ai/l) on the aphid life-table parameters led to significantly increase on the development time of third- and fourth-instar nymphs and preadult. Sublethal exposure to the insecticide mixture compromised aphid longevity, fecundity, and life-table parameters (r, R0, and T). Moreover, population growth and parasitism rate of the parasitoid were significantly compromised at both concentrations of the insecticide mixture under sublethal exposure. These results not only indicate the efficacy of thiacloprid + deltamethrin against the cotton aphid, but also raise concerns regarding its negative impacts on the parasitoid Aphidius flaviventris and caution against its use in pest management programs.
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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