| Delia antiqua (Meigen) is commonly known as "onion fly". These pests damage the garlic, onion and other Liliaceae vegetables mainly in the soil. Shandong Province is the main producing areas of garlic in China. So, onion flies occurred every year and are harming seriously. Nowadays, extensive application of organophosphate pesticides to control larvae leads to pests’ resistance and products’contamination. However, the adult trapping and killing is a novelty measure to control pests made use of pests’ tropism. Furthermore, adult trapping and killing is effective and environmentally-friendly. In this study, contact and stomach toxicity of four insecticides to the adults of Delia antiqua were determined in lab. Then, a trapping and killing fluid added with clothianidin and other insecticides was investigated in garlic fields. So the trapping and killing effects of this to mix fluid to adults of Delia antiqua (Meigen) was evaluated. Based on the early study in our laboratory,clothianidin performanced good control effect on onion maggot larvae, we established the method to determination of residues clothianidin in garlic. In addition, the residual dynamics and final residue of clothianidin in garlic were analyzed through field experiments. All of these can provide theoretical basis and applied technical guidance for onion fly decontamination control. The main results are as follows:1. Through the indoor test, we found that emamectin benzoate and clothianidin show the highest contact toxicity to the female adults of the onion fly, for the LD50were4.505μg/fly and20.021μg/fly respectively. They were higher than the contact toxicity of trichlorfon. And, the contact toxicity of spinosad (LD50) was only65.951μg/fly. The stomach toxicity of trichlorfon and clothianidin highest to adult female, for the LC50is0.850mg/L and1.050mg/L respectively. Followed, the LC50emamectin benzoate was1.765mg/L. And the stomach toxicity of spinosad was the lowest. Four kinds of pesticides slightly increased toxicity values with the extension of the observation time. However, the most obvious time effects were observed in emamectin benzoate and spinosad among these pesticides. We also found that the female adults were more tolerant to these insecticides. Comprehensive all above, clothianidin showed better control to onion fly adults in the four kinds of pesticides.2. In order to determine influences of insecticide to fecundity adults of Delia antique, onion fly adults were treated by stomach poisoning method of feeding. Then, egg number of survival adults were calculated after treatment by four kinds of insecticides. Results showed that clothianidin and spinosad reduced egg numbers significantly at the treated levels. As the accumulative total egg numbers were8.80/female and5.36/female in14days significantly lower than the control (25.52/female). However, adults treated with emamectin benzoate were18.20/female, which had little difference with the control. While, adults treated by trichlorfon did not differ significantly with the control. Moreover, in the range of0.3-2.4mg/L of clothianidin treatment,, inhibition to fecundity of the survival of the onion flies enhanced with the increase in concentration.3. Through the trapping and killing trial to onion fly adult in garlic fields, lothianidin and emamectin benzoate showed a high activity of trapping and killing. But chlorpyrifos, cypermethrin, spinosad, cyromazine, and fipronil performed low activity. This may due to the pesticides’ volatile odors or slow-release pharmaceutical and other factors. Three concentrations of clothianidin were tested. Results showed the effect of differences is not obvious under the comprehensive analysis. In addition, the trapping and killing fluid mixed with clothianidin, honey and water can be persistenced at least5days or more in the field.4. In this study, a rapid, sensitive, and environmental-friendly residue determination method based on QuEChERS for analysis of clothianidin residues in garlic was investigated. The analytes were extracted from the samples using acetonitrile combined with homogenization, purified by dispersion solid phase matrix extraction using100mg ODS-C18,100mg PSA and100mg florisil. Then samples were analyzed by LC/MS/MS with multiple-reaction monitoring (MRM) directly. The content was determined by external standard method. A good linear of the calibration curve was exhibited over a concentration range of1.0to100μg/L for clothianidin with a correlation coefficient of0.9995. Average recoveries for clothianidin in garlic ranged from95.7%～100.7%with a relative standard deviations (RSD) from0.7%～4.3%at spiked levels of5～50μg/kg. For clothianidin, the limit of quantification (LOQ) was1.55μg/kg, and the limit of detection (LOD) was0.47μg/kg. So, the method can be detect the residues of clothianidin in garlic accurately.5. Then dissipation of clothianidin was studied by the method above at two dosage of750ga.i./ha (the recommended dosage) and1500ga.i./ha. In the garlic samples, the concentrations of clothianidin were0.037and0.078mg/kg respectively7days after treatment and then decreased rapidly, reached0.009and0.015mg/kg after14days. The residues in garlic bulb only21days after treatment were0.003and0.011mg/kg_respectively, less than the MRLs (0.02mg/kg in garlic) set by Japan’s "Positive List System"... |
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