| Through systematic investigation, Symptoms of Grape downy mildew was first observed on March 28,2014 and got a peak on May 26th in observation nursery. The study found that was positively related to disease index and the average temperature of 5 days before the onset of, and downy mildew sporangium catch was significantly positive correlation, this shows that in the field of certain conditions, with grape downy mildew sporangia number increases, the field of downy mildew disease will increase significantly with the decrease in the number of grapes; on the contrary downy mildew sporangium catch, the field will be relatively reduced downy mildew disease. The field preliminary early stage and peak stage of disease could be predicted based on the meteorological data. From the beginning to capture the sporangium into the blade performance symptoms for 5 days or so, common incubation period of grape downy mildew was 4-6d.Grape downy mildew caused by Plasmopara viticola is one of main diseases on grapes. For screening fungicides to control grape downy mildew, metalaxyl, azoxystrobin, prochloraz, Dimethomorph, flumorph and mancozeb were tested by measuring the inhibition rate to sporangium germination. Result showed that the six fungicides could inhibit sporangium germination with EC50 respectively,121.28,279.45,113.45,25.83,154.67, and 51.86 μg/ml. Dimethomorph had very strong inhibition on grape downy mildew sporangium germination and could be used for potential control of grape downy mildew.Field tests showed that control effect against grape downy mildew of 30% metalaxyl into Dimethomorph water dispersible granule 1000 times,80% mancozeb WP 600 times,45% prochloraz EW 1000 times,50% Dimethomorph WP 1500 times,72% metalaxyl mancozeb WG 1000 times,25% Azoxystrobin suspending agent 1000 times,50% flumorph WP 1000 times was respectively 88.3%,63%,42.8%,87%,79.9%,85% and 88.2% after 14 days form the third spraying, could be used to control grape downy mildew. |
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