| Abamectin is a mixed natural product extracted by Streptomyces spp,which has the advantages of high efficacy,broad spectrum and low residue for various crop pests.It is one of the ideal bio-source pesticides in crop pest control.The droplet deposition characteristics of abamectin of different formulations by unmanned aerial vehicle?UAV?spray and conventional electric sprayer spray in rice canopy and the ir efficacies on Chilo suppressalis were compared in this paper,and the degradation dynamics of abamectin of different formulations in rice environment were measured.The adsorption behavior of abamectin in different soils?black soil in Heilongjiang,yellow brown soil in Shandong and paddy soil in Jiangxi?was tested,which provided reference for scientific application of abamectin and environmental safety assessment.The results are as follows:1.The droplet deposition characteristics of abamectin of five formulations by unmanned aerial vehicle?UAV?spray and conventional electric sprayer spray in rice canopy and their efficacies on Chilo suppressalis were compared.The results showed that the distribution density of droplets by UAV spray in upper layer of rice canopy was higher than that in middle layer and lower layer,and its distribution density was lower than that in electric sprayer.The deposition density results of droplet of abamectin with five formulations was as follows:dry suspension agent?DF?>water dispersion agent?WG?>water emulsion?EW??emulsifiable concentrate?EC?>suspension agent?SC?,particle size:DF<SC<EW<EC<WG.The deposition amount on rice was as follows:DF>EC?EW>WG>SC.Under the same formulations,the efficacy of abamectin by UAV spray on Chilo suppressalis of early rice and late rice was DF>EC>WG>EW>SC and DF>SC>EC>WG>EW,respectively.The efficacy of DF was the best,which was close to that by conventional electric sprayer.2.A method for the determination of abamectin residues in rice environment was established by improved QuEChERS-liquid chromatography.The samples were extracted by acetonitrile and purified by PSA+C18+GCB.Acetonitrile-aqueous solution?80?20,v/v?was used as mobile phase.The samples were separated by Zorbax Eclipse XDB-C18column,detected at 245 nm wavelength and quantified by external standard method.The detection limit and quantitative limit of abamectin in paddy water were 0.001 mg·L-1 and0.005 mg·L-1,respectively.The detection limits of abamectin in soil,brown rice,rice husk and rice plant were 0.005,0.01,0.01 and 0.005 mg·kg-1,respectively.The quantitative limits are 0.02,0.05,0.05 and 0.02 mg·kg-1,respectively.The recoveries of abamectin in paddy water,paddy soil,rice,plant and rice husk were 72.20%?109.69% with 2.73%?6.26%of RSD at spiked levels of 0.05?50 mg·kg-1.3.The degradation dynamics of abamectin with different formulations in rice environment were measured by HPLC.The half-life of abamectin in paddy water was 0.99?1.92 days,and its degradation rate was SC>EC=EW>DF>WG.The half-life of abamectin in rice plant was 1.21?4.17 days,and its degradation rate was SC>EC=EW>DF>WG.The half-life of abamectin in paddy soil was 2.76?3.17 days,and its degradation rate was WG>SC>DF>EC=EW.The final residue detection results showed that the residues of abamectin in rice plant and rice husk were 0.26?0.72 mg·kg-1 and 0.02?0.13 mg·kg-1,respectively.Abamectin was not detected in rice and soil.4.The adsorption-desorption characteristics of abamectin in three soils were determined by high performance liquid chromatography?HPLC?using oscillatory equilibrium method.The results showed that abamectin was strongly adsorbed by soil,and its adsorption intensity was positively correlated with organic matter?OM?and clay content of the soils.The adsorption capacity of the three soils was as follows:black soil in Heilongjiang>yellow brown soil in Shandong>paddy soil in Jiangxi. |
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