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. If the risk is “Low*” this means that the spore production was not high risk, but the forecast calls for more than three days of rain. (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. Despite some rains we observed, downy mildew risks were low this week; however, many growers reported downy mildew last week (which probably happened two to three weeks ago); thus, please keep your guard up for a few more weeks. Everybody seems to be 2-3 weeks ahead of the “typical” year. Let’s hope that good weather continues!

Please see last week’s post about the disease management options and a list of short PHI materials.