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.
The image above is just a summary. Please visit https://newa.cornell.edu/ to obtain more detailed information. You can check daily weather data as well as disease and insect pest model results including forecasted risks. We paid the annual fee so that growers in Virginia can freely access NEWA. Please take advantage of the resources. This information was made available through Wine Board-funded the Sentinel Vineyard project. We obtained NEWA weather stations that have been installed throughout the state.
More than a few days with downy mildew risks were observed in several regions in the past 7 days. The Northern VA region was relatively dry, but the situation may change in the near future based on the rains in the past several days. If you have not, please consider protecting your vines with downy mildew material(s). If you saw more than 2 inches of rain, it is probably a good idea to mix a phosphonate (i.e., a “phos acid”, such as Prophyt or Phostrol) for downy mildew and a DMI (e.g., Rally) for black rot to your next spray.
Many of our vines are still in the critical period for downy mildew, powdery mildew, and black rot cluster infection (i.e., bloom to ~6 weeks after bloom), so, please make sure to protect your vines. You can find specific materials information in this post (mid-season disease management), this post (VVA presentation), or this one (bloom time reminders). Reminder: the critical time to protect grape clusters from downy mildew, powdery mildew, and black rot starts at bloom and last 4-6 weeks (longer for V. vinifera).