UGA Extension Viticulture Blog

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.