| Fusarium head blight is one of the most important diseases affecting the yield and quality of wheat.The use of chemical pesticides is the main measure to control Fusarium head blight.Metconazole is a newly registered triazole fungicide in China,with only two registered formulation products,which can be used as a rotational or alternative pesticide for the control of Fusarium head blight.Study of the effectiveness of 10%metconazole microemulsion and 40%metconazole suspension against Fusarium head blight and fungal toxin contamination under plant protection drones and electric sprayers.A residue analysis method for metconazole in wheat plants and grains was developed to study the metconazole residue dissipation dynamics and final residue levels in the field of two pesticides under two application machines.The main findings were as follows:(1)A QuEChERS-UPLC-MS/MS method for analysing metconazole residues on wheat plants and grain was developed.showed good linearity in the concentration range of 4–500μg/L with correlation coefficients(R~2)of 0.9998–0.9999 and the lowest limit of quantification(LOQ)of 0.002 mg/kg,and the matrix effects were all weak matrix effects(-13.19–5.31%).The mean recoveries of metconazole in wheat plants and grain at 0.02,0.15,and 1.00 mg/kg spiked concentrations were 88.39–114.0%and 94.24–109.63%,respectively,with relative standard deviations of 3.18–7.70%and 0.49–6.32%,respectively.The accuracy,precision,and sensitivity of the method can meet the requirements of pesticide residue analysis.(2)Field efficacy trials of 10%metconazole microemulsion and 40%metconazole suspension for the control of Fusarium head blight under two types of application machinery,plant protection drones and backpack electric sprayers,were conducted.The results showed that at the recommended dose(225 g a.i./ha),the disease spikes of Fusarium head blight were 10.02-11.20%and the efficacy was 81.55-83.74%after the application of metconazole with the drone and electric sprayer,indicating that metconazole had a good control effect on Fusarium head blight.10%metconazole microemulsion was 83.50–84.74%more effective than 40%metconazole suspension.The effectiveness of 10%metconazole microemulsion was slightly higher than that of 40%metconazole suspension at 81.55-82.04%,but the difference was not significant.10%metconazole microemulsion had a certain inhibitory effect on the formation of heavily diseased spikes of Fusarium head blight,and no grade 7 diseased spikes were seen after application under either of the application machines.(3)The safety evaluation of the two metconazole formulations on wheat was carried out.The results showed that after two applications at the recommended dose(225 g a.i./ha),no symptoms of drug damage were observed in each metconazole agent treatment group at 1,3 and 7 days,and wheat grew well;the mean SPAD values of relative chlorophyll content of wheat at harvest were 31.67–33.51,which were2.76–8.10%lower than those of the clear water control(34.46),and the differences were not significant(P>0.05),metconazole had less effect on the chlorophyll content of wheat at harvest.It can be seen that 10%metconazole microemulsion and 40%metconazole suspension were safe for wheat when applied at the recommended dose of225 g a.i./ha under different application apparatus.(4)The effect of metconazole on the control of mycotoxin contamination in wheat was investigated.The results showed that the total amount of DON toxin in wheat grain under clear water treatment was 1140μg/kg,which exceeded the limit of DON toxin of 1000μg/kg as stipulated in GB 2761-2017.After the application of 10%metconazole microemulsion and 40%metconazole suspension at the recommended dose of 225 g a.i./ha using drones and electric sprayers,the detection values of total grain DON ranged from 35 to 615μg/kg,which were lower than the limits,indicating that both 10%metconazole microemulsion and 40%metconazole suspension could reduce the DON toxin contamination of wheat grain under both application devices.Among them,the plant protection drone application of 10%metconazole microemulsion was the most effective,with a DON toxin content of 35μg/kg in wheat grains after application,and the inhibition effect was as high as 96.93%.The ZEN toxin content in all treatment groups was below the minimum detection limit of 0.002 mg/kg.(5)Field experiments on the ablation of metconazole in wheat plants were carried out.The results showed that the dynamics of metconazole disintegration in wheat plants at the recommended dose of 225 g a.i./ha were in accordance with the first order kinetic equation.The abatement half-lives were 3.006 days and 3.235 days for the 10%metconazole microemulsion and 40%metconazole suspension,respectively,applied by drone.For the electro sprayer application of 10%metconazole microemulsion and 40%metconazole suspension,the abatement half-lives were 7.427 and 5.875 days,respectively;the metconazole residues in the plants were significantly reduced by more than 90%in all treatment groups at 26 days.(6)The final residues of metconazole in wheat grains were determined.The results showed that at the recommended dose of 225 g a.i./ha,the final residue levels of metconazole in wheat grain final residue samples were 0.0127-0.0465 mg/kg when sprayed with 10%metconazole microemulsion and 40%metconazole suspension by plant protection drones and electric sprayers,which were both lower than the maximum residue limits stipulated in GB 2763-2021 in China Based on the final residue results,the recommended application dose for 10%metconazole microemulsion and 40%metconazole suspension was 225 g a.i./ha,with two applications at a 7-day interval,which could be applied by plant protection drones and electric sprayers. |
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