Here are snapshots 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. N/A means there is no data or some issues with the NEWA or the weather station location. This year, we have been using a different downy mildew model due to inconsistency with the NEWA model. This model uses the past five days of weather to estimate spore production and the next seven-day forecast to estimate the infection risk. If the risk is “High” with a pink highlight, there were enough days with the risk of spore production and more than a few days of rains expected in the next seven days. (Note: yellow highlight ones, which we do not have this week, means the risk of rain in the next seven days is low.)
You can ignore BR and Ph at this point of the season because clusters are no longer susceptible to the infection. We will focus mainly on downy mildew. As we expected, several rain events occurred throughout the Commonwealth, and some locations, especially in the south, resulted in high downy mildew risks for the next five days. For those areas, if your vines were not protected for more than 7-10 days, placing another protection before the next rain event is probably a good idea, which seems to happen on or around Thursday and a few more in the next week. (i.e., you may have a window of spray opportunity from Friday to Monday, depending on your location.)
