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Downy, Botrytis, sulfur burn, and open house

With recent rain events and warm and humid nights, the risk of downy mildew and Botrytis are probably high in many areas of Virginia. For example, I counted seven days (at Winchester, VA) and eleven days (at Rustburg and Scottsville, VA), with downy mildew infection events in the past two weeks according to the NEWA model ( It is very important to keep your vines protected, and if you think you need to have a kick-back activity against downy mildew to counteract the recent rain event that your previous spray might not have provided good coverage, add a phosphorous acid material such as Prophyt or Phostrol. 

Please refer to this list of materials with short PHI since some of the cultivars are getting very close to harvest. Note: although both sulfur and copper have a short PHI, we typically do not recommend spraying these materials within 3-4 weeks of harvest due to its potential negative impacts on the fermentation or wine quality. 

When some of us ended up spraying when the weather condition is not favoring (i.e., leaves are wet), you may see chemical burn from sulfur. It tends to happen when sprayed leaves are still wet and the temperature shoots up to mid-90F or higher soon after the spray. A typical symptom is brown burn marks in the middle of leaves where you would expect spray residues stayed wet. The picture below is an example from my vineyard where I had to spray in drizzle last Sunday morning. (In my defense, the forecast did not call for rain and I did not even see it coming on the Doppler radar...) Unlike diseases, you will likely see symptomatic leaves uniformly happening throughout the vineyard. Or you may see in spots where you tend to slow down your tractor and thus spray more amount than other places.

Last, but not the least, we will have a virtual open house tomorrow starting noon. Please join us if you have time. You can visit us while eating lunch!

Virtual Open House: Virginia Tech’s Alson H. Smith Jr. Agricultural Research and Extension Center (AREC), Frederick County, VA

In lieu of public gatherings, the faculty, staff, and students at Virginia Tech’s Alson H. Smith, Jr. AREC in Frederick County will present a “virtual” open house on August 15, 2020 from 12:00 to 2:00 pm. The AREC is a unit of Virginia Tech’s College of Agriculture and Life Sciences and is primarily focused on research and educational programs that serve the tree fruit and wine grape industries. Center personnel will explain and illustrate their research and outreach efforts to combat invasive pests such as brown marmorated stinkbug, avoid spring frost damage to tree fruits and grape, evaluate new grape varieties for table and wine use, and much more. The public is encouraged to “attend” via a Zoom video conference which you must pre-register for: ( After registering, you will receive a confirmation email containing information about joining the meeting.  For more information, contact Debra Marple: 540-232-6031 or Please visit our website to learn more about our current research on tree fruit and wine grapes.

Facebook Event Site:

Virginia Cooperative Extension programs and employment are open to all, regardless of age, color, disability, gender, gender identity, gender expression, national origin, political affiliation, race, religion, sexual orientation, genetic information, veteran status, or any other basis protected by law. An equal opportunity/affirmative action employer. Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Administrator, 1890 Extension Program, Virginia State University, Petersburg.

If you are a person with a disability and desire any assistive devices, services or other accommodations to participate in this activity, please contact Debra Marple: 540-232-6031 or during business hours of 9:00 a.m. and 4:00 p.m. to discuss accommodations 5 days prior to the event.

*TDD number is (800) 828-1120.


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