| In this paper,three kinds of application instruments and two pesticide additives were used in citrus orchard to optimize the effective method of application for citrus orchard.To study the distribution and deposition of typical chemical pesticides(buprofezin,acetamiprid and difenoconazole)on citrus,and to Investigate the effect of different application methods on the deposition of pesticides on citrus,improve the utilization rate of pesticides use to provide data support for orchard pesticide reduction.A liquid chromatography-tandem mass spectrometer was used to analyze the deposition of buprofezin,acetamiprid and difenoconazole in citrus.The citrus leaf samples were extracted with acetonitrile and extracted by sonication and vortex extraction,sodium chloride salting out,primary secondary amine(PSA)purification,and finally LC-MS/MS detection.Citrus peel and soil samples were extracted with acetonitrile and ethyl acetate,extracted by ultrasonic and vortex,sodium chloride salting out,primary secondary amine(PSA)purification,and finally detected by LC-MS/MS.The results showed that the recoveries of buprofezin,acetamiprid and difenoconazole in citrus leaves were 72.30%～92.05%,73.46%～83.18% and 77.35%～94.30%,respectively.And the relative standard deviations were 2.40%～5.21%,3.22%～3.82% and 1.45%～3.87%.The recoveries of buprofezin,acetamiprid and difenoconazole in citrus peel were 96.13%～102.91%,94.99%～106.67% and 75.29%～94.97%,respectively.And the relative standard deviations were 1.07%～2.00%,1.40%～3.79% and 1.56%～2.38%.The recoveries of buprofezin,acetamiprid and difenoconazole in soil were 90.81%～106.12%,87.15%～104.60% and 84.46%～109.05%,respectively.And the relative standard deviations were 2.63%～4.48%,1.57%～5.50% and 4.54%～4.98%.The accuracy,precision and sensitivity of this method can meet the requirements of pesticide residue analysis.The adaxial surface tension value of citrus leaves was 33.59 mN/m,and the abaxial surface tension value of citrus leaves was 32.78 mN/m.The test results show that the critical micelle concentration of organic silicone additive is 240 mg/L,the corresponding surface tension value is 31.01 mN/m,and the critical micelle concentration of mineral oil additive is 250 mg/L,corresponding to the surface tension value.30.20mN/m.Separately,the mineral oil concentration of 1 g/L and the organic silicon concentration of 1 g/L were used to formulate the pesticide.The concentration of mineral oil was higher than the critical micelle concentration of mineral oil 250 mg/L.The organic silicone concentration was higher than the organic silicone criticality.When the micelle concentration was 240 mg/L and the concentration of the drug solution reached the critical micelle concentration,the surface tension of the drug solution did not change or changed little with the increase of the additive concentration.When the mineral oil additive is added to the liquid,the droplets are on the citrus leaves,and after 10 s,the droplets are completely wetted and spread;when the organic silicone additive is added to the liquid,the droplets are on the front and back of the citrus leaf,after 5 s Afterwards,the droplets completely wet the spread.Therefore,the addition of suitable pesticide additives will help improve the wetting performance of the pesticide solution on citrus leaves.The deposition and distribution of the active ingredients in different parts of the citrus tree were analyzed by significance.The results showed that conventional electric sprayers,electrostatic sprayers,and air-assisted sprayers applied pesticides on citrus and had a significant effect on the deposition of pesticides on citrus.The difference(P<0.05),using conventional electric sprayers,electrostatic sprayers,and air-assisted sprayers for 2 h to 10 d,the deposition of acetamiprid on citrus leaves was 0.17 mg/kg～0.38 mg/kg,0.16 mg/kg～0.84 mg/kg,and 0.17 mg/kg～0.64 mg/kg,respectively.and the deposition of difenoconazole on citrus leaves was 0.10 mg/kg～1.49 mg/kg,0.58 mg/kg～3.53 mg/kg and 0.38 mg/kg～2.70 mg/kg,respectively.the deposition amounts of buprofezin on citrus leaves were 0.14 mg/kg～4.73 mg/kg and 0.15 mg/kg～9.56 mg/kg and 0.15 mg/kg～6.68 mg/kg,respectively in Sichuan.Three sprayers also showed the same trend in pesticide deposition on citrus peel.Mineral oil was added for pesticide application.For mineral oil and water control for 2 h to 10 d,mineral oil had no obvious effect on the deposition of the three pesticides on citrus.Organic silicone was added for pesticide application.Silicon dioxide and clear water were added for 1 day to 10 days.Organic silicone additives were added.The amount of pesticide deposited was significantly higher than that of the clear water control,it shows that organic silicone can effectively sustain the amount of pesticide deposited on the target site.The addition of mineral oil additives did not significantly improve the deposition of pesticides.Through the study of the distribution of sediments after application in citrus orchards,the pesticide residues in the orange leaves accounted for 59 to 79% of the percentage of the three percentages,and the pesticide residues in the peel accounted for 21 to 40% of the percentage of the three percentages.The relative content was the smallest,and the percentage of pesticide residues in the soil was less than 5%.Compared to conventional sprays,the content of pesticides in the electrostatic spray and effluent sprayed soil was smaller,all less than 1%.By studying the dynamics of digestion under different application methods,in Pujiang Sichuan,the half-life of acetamiprid was 4.6 d to 9.7 d,the half-life of Difenoconazole was 3.4 d to 5.6 d,and the half-life of buprofezin was 1.5 d to 2.7 d under different modes of application.In Huishui Guizhou,the half-life of acetamiprid was 1.3 d to 2.0 d the half-life of difenoconazole was 2.0 d to 2.9 d under different application methods,and the half-life of buprofezin was 1.2 d to 2.4 d under different application methods. |
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