Grape disease risks 4/20-4/27/2022

It looks like this morning did not get too cold for grapes. A quick look at the low temperature showed that some parts of northern and northcentral VA saw 33F or so, but the rest of the state was in the upper 30s and lower 40s.

As a part of a Wine Board-funded the Sentinel Vineyard project, we received NEWA weather stations that have been installed throughout the state. There are several more to be installed in the next year or so, but now we have a good number of stations to be able to show what’s going on in different parts of the state. 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.

There was a day with the risk of Phomopsis infection in the southwest, central, and southeast VA. It looks like in the southeast, there were two days with the risk of downy mildew infection. Although you may not see downy mildew this early in the season, the downy mildew pathogen can be active (= awaken from the winter dormant stage) right now. Also, the temperature has been warm enough for some days for the powdery mildew risk to be high. Make sure to include a downy mildew material (Mancozeb or captan or fixed copper will do) and a powdery mildew material (sulfur or fixed copper is a good choice at this time of the season) in your spray materials.

Reminder on Phomopsis spray.

Reminder on early-season disease management (PowerPoint slide)

I hope this type of information is helpful to you to decide the course of action for your next fungicide application.

The image above is just a summary. Please visit 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.

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This Post Has 6 Comments

  1. Thanks, Mizuho,
    This post was especially helpful to me, reminding me that some (most?) need to be applied in advance of anticipated rainfall. Even though you listed the risk of Phomopsis in our area as zero,
    we expect one-third of an inch of rain today, so I sprayed Friday, in anticipation.

    Separately, are these risk announcements going to be routinely pushed to your distribution list?

  2. Thanks Mizuho. We have had over 1.25 inches of rain in the last 48 hours and there is a mist coming off the mountain that does not look like it is going to clear anytime soon. Is there any news on the replacement rain gauge?
    BTW the dates are wrong on this email. We are now in May already.

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