Effect Of Pyraclostrobin On The Control Effect Of Two Kinds Of Plant Fungal Diseases And The Effect Of Target Area Residue

The design and implementation of the premise of using spray application methods in the field of greenhouse,investigation of pyraclostrobin prevention effect on watermelon powdery mildew and cucumber downy mildew,through the investigation on the occurrence of the disease in field,calculate the disease index and control effect of the target field;back to the area sample collection after the establishment of pyraclostrobin in tomato leaves on the residue analysis method in leaves of watermelon,cucumber leaves,calculated by Masslynxx residue data,further summarizes the two residue dissipation dynamics of fungicides in leaves of watermelon,cucumber and tomato leaves on the leaves.Then the field bioassay data and target residue data were combined to get the best interval and the lowest effective dose in each treatment group.The results of the study are as follows:The control effect of pyraclostrobin on watermelon powdery mildew under different dosages was compared.It was found that the different control concentrations had different effects on watermelon powdery mildew,and its control effect increased with the increase of dosage.At 112.5 g/hm~2 and 150 g/hm~2 treatment concentration,the control effect of watermelon powdery mildew could still be maintained within 79.70%days in 21 days.Meanwhile,50 g/hm~2 and 75 g/hm~2 treatment concentration could also control more than 60%.The detection results of target residues showed that the half-life of watermelon leaves increased from 7 days to 14 days with the increase of pesticide dosage,which basically coincided with the reduction of field efficacy.In the treatment group less than the recommended dose(55 g/hm~2),the target residues in leaves were0.146 mg/kg,and the control effect of pyraclostrobin on field watermelon powdery mildew was 77.2%.Therefore,in the recommended treatment group(55 g/hm~2),when the residue level of leaf target was below 0.146 mg/kg,it should be applied again to prevent the disease from spreading in large area.The safe intervals of 50 g/hm~2,75g/hm~2,112.5 g/hm~2 and 150 g/hm~2 on watermelon were 7 days,10 days,14 days and13 days,respectively.The control effect of pyraclostrobin on cucumber downy mildew was compared.It was found that different control concentrations had different effects on cucumber downy mildew,and its control effect increased with the increase of dosage.Under the concentration of 40 g/hm~2,the control effect of cucumber downy mildew could still keep 72.2%within 21 days,and the control effect of 15 g/hm~2,20 g/hm~2 and 30 g/hm~2could also reach 56.3%to 70.5%.The detection results of target residues showed that the half-life of cucumber leaves increased from 14 days to 22 days with the increase of pesticide dosage,which basically coincided with the field efficacy.In the less than recommended dose treatment group(15 g/hm~2),its half-life was 14 days.At this time,the effect of pyraclostrobin on the field cucumber downy mildew was 58.1%.Therefore,in the less recommended dose group(15 g/hm~2),when the residue level of leaf target was lower than 0.054 mg/kg,it should be applied again to prevent the disease from spreading in large area.The half-life of 15 g/hm~2,20g/hm~2,30 g/hm~2 and 40 g/hm~2pyraclostrobin on cucumber were 14 days,16 days,19 days and 22 days respectively.