Inpact of application frequency on control effect of rice neck blast and residue of fungicides in brown rice
The aim of this experiment was to determine the control effect of eight common fungicides on rice neck blast and the residue in rice after application at different frequencies.Three application frequencies were set up,including once,twice or three times in the experiment.We monitored the effect of different treatments on rice neck blast,and the method of ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)was used to determine the residue in different treatments of rice.The results showed that for any of these fungicides,the more times of application,the better the control effect of rice blast and the higher the reside of fungicide in rice.When applied once,the control efficacy of pyraclostrobin and azoxystrobin was more than 90％.When applied twice,the control efficacy of tricyclazole,pyraclostrobin and azoxystrobin was more than 90％.When applied three times,the control effect of tricyclazole,isoprothiolane and azoxystrobin was more than 90％.The final residue exceeded the maximum residue limit in the treatment of three times application of isoprothiolane,while other treatments in this experiment did not lead to excessive residues.In conclusion,the application of tricyclazole,pyraclostrobin or azoxystrobin once at the break stage and the other time at full heading stage can effectively control rice neck blast without residual risk,and is suitable for rice green production.
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