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Downy Mildew, Powdery Mildew, and Black Rot Warnings

We are starting to see diseases pop up on both European vinifera and hybrid grapes.  For some of these, such as anthracnose and Phomopsis, much of the initial infection occurred much earlier.  The goal now would be to prevent secondary spread — especially to developing clusters.  Relative downy mildew, Sarah Campbell (UGA grad student) reported limited downy mildew leaf infections in all untreated and strobilurin (Abound and Pristine) test plots this week — all three locations.  This clearly proves that we can’t trust this fungicide class for management of downy mildew, and strobilurins would need to be mixed with either mancozeb or Captan products at a minimum for downy mildew control.  The other downy mildew fungicides appear to be holding well for the moment. Cheng-Fang Hong (UGA grad student) indicated that the Italian disease prediction model is now predicting strong secondary spread of downy mildew, and both powdery mildew and black rot environmental conditions are now ideal for the development of these diseases.  Dew is sufficient for infection of downy mildew and black rot, so even though we have had a little less rain over the last couple of weeks, we are still having more than enough moisture for epidemic development.  Powdery mildew actually will infect better under drier conditions, so you really need to concentrate your fire on this disease at this time.

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About Phil Brannen

Phil Brannen is a Professor in the Plant Pathology Department at the University of Georgia. He attended the University of Georgia for his undergraduate degree in Plant Protection and Pest Management, where he also received an M.S. in Plant Pathology, followed by a Ph.D. in Plant Pathology from Auburn University. He has extensive experience with disease management programs in numerous cropping systems. He serves as the extension fruit pathologist for Georgia – conducting research and technology transfer for multiple fruit commodities. His efforts are directed towards developing IPM practices to solve disease issues and technology transfer of disease-management methods to commercial fruit producers. He also teaches the graduate level Field Pathology Course, the History of Plant Diseases and their Impact on Human Societies Course, team-teaches the IPM Course, coordinates the Viticulture and Enology in the Mediterranean Region Course (Cortona, Italy), and guest lectures in numerous other courses throughout the year.