Powdery Mildew Resistance Survey

Clint Thompson Georgia, Grapes, Top Posts

File photo shows muscadine vines in a vineyard.

According to the UGA Extension Viticulture Blog, University of Georgia researchers are asking grape producers if powdery mildew has been spotted in their vineyards. UGA would love to sample it, and it could mean that the fungicide program is breaking down due to resistance development in the powdery mildew fungus.

UGA graduate student Brooke Warres is working on QoI and DMI fungicide resistance in powdery mildew. She can take swab samples of the mildew from any part of the grapevine to test for mutations associated with resistance to these chemical classes. With this information, UGA can better understand resistance patterns in Georgia and determine how widespread these mutations are throughout the state.

As producers are scouting their vineyard at the end of the season, UGA suggests looking inside the canopy to check for white to gray fungal growth of powdery mildew — predominantly on the upper leaf surfaces. Depending on how well it has been controlled, it may also be self-evident on the canopy exterior. If you are finding this disease, please call Brooke at 678-642-2183 or email at Brooke.Warres@uga.edu so she can visit to take a quick sample. With these samples, she will be able to let you know if you currently have QoI and/or DMI resistant populations in your vineyard. This should help you to plan your spray program for next season.