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Crown Gall on Muscadine Grapes in North Georgia

I was at a muscadine meeting in Americus, GA earlier this week (Thursday), and I made comment on how I have never really observed significant crown gall on muscadine grapes in Georgia. I scheduled a muscadine grape visit with a producer near Ellijay, GA the next day, and I can now say that I have observed significant crown gall on muscadine grapes in Georgia.  In this case, all diseased vines were just over a year old, and I suspect that winter injury (2017/2018) resulted in subsequent crown gall. Crown gall is caused by a bacterium that activates galling following injury — such as that observed with cold damage and weed trimmers for example. Of interest, two year old vines did not have galling, which may possibly indicate that more mature vines are less susceptible to winter injury; the 2016/2017 winter was unseasonably warmer than average, so limited if any winter damage would have occurred — even at higher elevations. It also could mean that one lot was infected with the crown gall bacterium, while another was not. As producers are thinking about which grape varieties to plant in the more northern regions of our state, many are starting to turn to muscadines.  We need better research-based information to help us determine the elevations and/or USDA zones where muscadines can be successfully grown in the northern part of our state. If I were a producer, I would consider trying some muscadines at relatively higher elevations, but I would diversify where possible — planting other hybrids or more cold-tolerant grapes as well.  As we review more varieties over time, through research and the school of hard knocks, we will learn one way or another which grape species and varieties will work for our various grape-growing regions.  We are definitely still in a learning phase.

Crown gall on muscadine grape vine near Ellijay, GA.

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Phil Brannen

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.