Grape Disease Risks 9/6 – 9/13/2023

According to the Sentinel Vineyard Core Group discussions, many growers are harvesting early season cultivars right now. Sugar accumulation and the cleanliness of the crop has been particularly good this year. We will see how it will translate into the wine quality!

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. At this point, you can ignore Phomopsis and black rot since Phomopsis should be done with their spore production, and clusters are resistant to black rot infection. This information was made available through the Wine Board-funded Sentinel Vineyard project.

Now we have a wet week after three weeks (for the Central and Southern VA) and after almost entire season (for the Northern VA). At this point what we need to take care of are downy mildew (on leaves) and late-season rots. Remember that your spray decision should not solely rely on weather conditions. It is crucial to consider factors such as the cultivar and the disease history in your vineyard. Please see the slide set from our previous meeting discussing late-season rot management. Some products have a relatively long PHI (e.g., Ranman’s PHI is 30 days). This post contains the list of fungicides with short PHIs. Make sure to read the label or refer to our PMG.  

The image above concisely summarizes the past seven days, aiding your understanding of recent events. However, the best action is proactively safeguarding your vines. For more comprehensive information, please visit, where you can access detailed daily weather data and disease and insect pest model results, including forecasted risks. We have covered the annual fee to ensure free access for growers in Virginia to the NEWA platform.

Virtual Vineyard Meeting

Our next Virtual Vineyard Meeting (and will be the last one for the season) will be held tody (9/14/2023) from 1 PM. If you have not registered, please visit this post.

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