Here’s a snapshot from the last week, showing the number of days with the risk of each disease: Ph = Phomopsis, PW = Powdery mildew, BR = Black rot, and DM = Downy mildew. This information was made available through the Wine Board-funded Sentinel Vineyard project.
It looks like we had another nice dry week, and no major risks were observed. However, this is a prime time for Phomopsis activity. Thus, if you see the rain coming into your area, it is better to protect your vines. Here’s a link to early-season grape disease management reminders. Unfortunately, the DM model was not working today. However, based on low risk of black rot (i.e., another dry week), I think we are still in a good shape.
The image above is just a summary of the past seven days. Please visit https://newa.cornell.edu/ to obtain more detailed information. You can check daily weather data and disease and insect pest model results, including forecasted risks. We paid the annual fee so that growers in Virginia could freely access NEWA.
The risk information above is just output from the model to help you understand what happened. However, you need to prepare your sprays to protect your vines. One way to use this information is to adjust your spray intervals. If you see many days with disease risk(s), then you may need to shorten your spray interval, or if you missed a material for downy or black rot, then you may wish to spray material(s) with kick-back activity. Or you may wish to extend your spray interval, if you have not seen much risks as we have been experiencing this year. However, with incoming rain forecasted during the weekend, I personally think it is worth protecting your vines this time around. It is important to understand that the spray decision must be based not only on the weather condition but also on the cultivar and history of the disease(s) in your vineyard.