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Non-target toxicity of insecticides and fungicides on the predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) used in vegetable
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عنوان دوره: دومین کنگره بین المللی حشره شناسی ایران
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چکیده
Nesidiocoris tenuis (Heteroptera: Miridae) is one of the most abundant zoophytophagous plant bugs in tomato crops. It preys on whiteflies and other small pests such as spider mites, leafminers and early instars of Lepidoptera. It is mass-reared and released in augmentative biocontrol programs aimed at controlling whiteflies and Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in greenhouses and also useful under open field conditions. We evaluated lethal and sublethal toxicity of three insecticides (cypermethrin, pyripoxyfen, spirotetramat) and seven fungicides (benomyl, chlorothalonil, copper oxychloride, cyazofamid, fluopicolide + propamocarb hydrochloride, penconazol, trifloxystrobin) against N. tenius commonlly used in tomato production and also in several other vegetable and fruit crops. Experiments included (i) release of predator adults onto tomato plant sprouts containing dry residues of insecticides or fungicides and (ii) multiple exposure of the predator to these chemicals through topical sprays, foraging on treated sprouts and feeding on treated eggs of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae). Predator survival, reproductive capacity and reduction coefficient (Ex) were investigated as indicators of lethal and sublethal effects and compared against International Organization for Biological Control (IOBC) classification: (1) harmless: Ex< 30%, (2) slightly harmful: 30% <Ex< 80%, (3) moderately harmful: 80% <Ex< 99%, and (4): harmful: Ex> 99%. Tested insecticides and fungicides were all harmless when predator was exposed only to their dry residues. However, multiple exposure to cypermethrin, benomyl, chlorothalonil, copper oxychloride and trifloxystrobin caused significantly mortality of N. tenuis adults. Only cypermethrin was categorized harmful which impacted predator reproductive capacity resulting in Ex of 99.92%. Findings suggest that all tested insecticides except cypermethrin and fungicides were harmless to N. tenuis and compatible for integrated crop management.
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