Virginia Grape Disease Updates

It looks like we will see a series of rain events in the next few days. As noted in the previous virtual viticulture meetings, we had several black rot and downy mildew infection events in the past two weeks, and some people start to see the development of these diseases. Some growers asked me how long does it take for fungicide materials to be dry enough to be rainfast. It depends on your sprayer, droplet size, weather conditions, etc., but typically, I hear 1.5 hours to 2 hours are required. Some fungicide labels show the expected dry time. The other common question is about how much rain is enough to wash off fungicide materials from the plant surface. Please check the excellent articles from Dr. Annemiek Shielder ( link 1 , link 2 ). She talks about the rain fastness of some products using a rain simulator. It looks like there is a sharp drop only after 0.04 inches of rain, but after that, the material tends to stay on the surface, even if there are more precipitations. In the art...

Thanks for all who were able to make it to our virtual meeting this afternoon! The file below is the slide set I used today, the link will open a pdf file in a new window. Critical time *very quick* grape disease management reminders  - please see the previous two presentation slides for more information! 1) June 4th meeting , 2) PSU meeting .

Thanks for all who were able to make it to our virtual meeting this afternoon. The file below is the slide set I used today, the link will open a pdf file in a new window. Grape disease management reminders, 4 June 2020