Study On Screening And Substitution Of Green Production Pesticides For Rice In Shanghai

Wheat,corn and rice are the main crops in China.Among them,large planting area and high yield are the characteristics of rice.About two-thirds of our population uses rice as a staple food.However,rice is vulnerable to seasonal pests and diseases during planting,and rice blast is one of the most common diseases.Because chemical control has the characteristics of high efficiency and economy,it has been used as the main measure to prevent and control rice blast.However,the non-standard use of pesticides in the rice planting process can easily lead to excessive residues in rice.At present,the era of"green"as the consumption theme,green food has achieved unprecedented development,the quality inspection and safety supervision of rice are inseparable from the people's life,and this issue has caused great concern of the masses.In order to understand the pesticide residues in rice sold in Shanghai,this study established a new pesticide multi-residue detection method.Field sampling and investigation of rice samples sold in Shanghai showed that pesticide residues were detected in the rice.Therefore,in view of the current pesticide residues in rice,this study intends to conduct a two-year field test in Fengxian District of Shanghai in 2018and 2019 by using Nanjing 46 as a test rice planting variety.The dynamic digestion changes,the final residual content and the difference in the control effect of rice blast were studied in order to make recommendations for green medicine for rice production.The main research conclusions are as following:?1?An analytical method was developed for the simultaneous detection of 42pesticide residues in rice and rice stalks by Qu ECh ERS pre-treatment technology combined with ultra-high performance liquid chromatography-tandem mass spectrometry.The linear relationship between the mass concentration of 42 pesticides and the corresponding peak area was good,R²>0.99,the detection limit is 0.001?0.002 mg/kg.Under the five added levels of 0.01,0.02,0.05,0.1 and 0.2 mg/kg,the average recoveries of 42 pesticides in rice and rice stalks were 70%to 117%,and the relative standard deviations?RSDs?were 1.5%?15%and 0.9%?15%,respectively.The accuracy and precision of the method meet the requirements of pesticide residue test guidelines,which can be used for the determination of multiple pesticide residues.?2?Green production pesticide screening was conducted on rice sold in Shanghai.Rice samples were detected 11 pesticide residues.The results showed that the pesticides detected in the harvested rice all meet the requirements of pollution-free rice,but if green rice certification is to be carried out,it is necessary to guide the production of rice.?3?Through laboratory experiments,the mycelial growth rate inhibition method was used to determine the virulence of tricyclazole,azoxystrobin,ethoxylate and epoxiconazole to the rice blast fungus.The experimental results showed that azoxystrobin has the highest bacteriostatic activity,EC₅₀=0.5595 mg/L,which of epoxiconazole and tricyclazole were better.Ethoxylate has the worst bacteriostatic activity,EC₅₀=35.3353 mg/L.?4?Through field experiments,the dynamic digestion laws of tricyclazole,azoxystrobin,ethoxylate and epoxiconazole pesticides on rice stems and leaves were studied.The results showed that the digestion dynamics of the four pesticides on rice different treatments.In 2018,the pesticide digestion dynamics of experiments,the half-life of tricyclazole in rice stalks and leaves were 2.2?2.4 d and 2.8?5.1 d,the half-life of azoxystrobin in rice stalks and leaves were 2.4?3.6 d and 4.0?5.8 d,the half-lives of ethoxylate in rice stalks and leaves were 1.6?3.1 d and 3.3?3.8 d,and the half-lives of epoxiconazole in rice stalks and leaves were 2.0?3.7 d and 2.4?4.2 d;In 2019,the digestion dynamics of pesticides in experiments,the half-life of tricyclazole in rice stalks and leaves were 4.0 d and 3.9 d,the half-life of azoxystrobin in rice stalks and leaves were 2.8 d and 4.6 d,and the half-lives of ethoxylate in rice stalks and leaves were 2.4 d and 2.7 d,respectively.The half-lives of epoxiconazole in rice stalks and leaves were 3.5 d and 4.4 d,respectively.The half-lives of the four pesticides in rice stalks and leaves were less than 30 days,and they were all easily degradable pesticides.?5?Through field experiments,the residues of tricyclazole,azoxystrobin,ethoxylate and epoxiconazole pesticides on rice were studied.In 2018,the test results showed that only epoxiconazole was detected in the brown rice under the break stage treatment,and the final residual amount was ND?0.025 mg/kg.Only tricyclazole and epoxiconazole were detected in the brown rice under the heading treatment.Pesticides with final residues of ND?0.096 mg/kg and ND?0.050 mg/kg,respectively.Only tricyclazole and epoxiconazole were detected in brown rice under the treatment of both the opening and heading stages.The final residues were 0.009?0.126 mg/kg,0.011?0.095 mg/kg;residual results of the drug reduction test in 2019 showed that the residual content of tricyclazole in brown rice was 0.061?0.129 mg/kg,and the residual content of epoxiconazole was 0.075?0.126 mg/kg.Neither azoxystrobin nor ethoxylate were detected.Field test results showed that tricyclazole and epoxiconazole were more likely to remain in the heading stage than in the breaching stage under different treatment periods.The residues of tricyclazole and epoxiconazole in the superimposed treatment at the opening stage and the heading stage were higher than those of the treatment at the opening stage or the heading stage.?6?Through field experiments,the control effects of tricyclazole,azoxystrobin,ethoxylate,ethereal bacteria·flucyclozole,and Bacillus subtilis on rice blast and their effects on rice yield were studied.The test results in 2018 showed that tricyclazole and ethereal bacteria·flucyclozole pesticides had two treatments at the break and heading stage,which were better than one treatment at the break stage,and azoxystrobin was better at one treatment at the break stage.At the same time,in two processing effects,azoxystrobin treatment had the highest yield of rice in the treatment period than other treatments,which was 9.52 t/hm²;The results of the test in 2019 showed that tricyclazole>azoxystrobin>bacillus subtilis>ethereal bacteria·flucyclozole,but the highest yield of rice treated with azoxystrobin was 9.52 t/hm².This study showed that spraying azoxystrobin once during the rice cracking period can better control rice blast,which has a high yield,and was not easy to remain.Therefore,azoxystrobin can replace tricyclazole in green medicine.