Crown gall can sometimes be confused with either leaf roll virus or Pierce’s disease. In general, if a plant is a completely brilliant red, this is likely caused by crown gall or some trunk injury.  Pierce’s disease and leaf roll viruses can also have reddened leaves or leaf margins, so this is a little confusing for sure.  However, if the entire plant is red, looking for galls at the crown or graft-union area will usually help to determine whether crown gall is the culprit disease. If there is any good news for crown gall, it is that leaf roll viruses and Pierce’s disease are more problematic diseases.  For crown gall infested vines, it is probably best to just destroy these plants, pulling them out with a tractor or something of that nature.  If the gall is only on one side, they might survive.  However, where the entire plant is red, this usually means they are girdled and on their way out.  Bringing in disease-free plants is critical to crown gall management.  The bacteria is generally systemic in plants and only presents itself as a gall following injury – winter injury, weed wackers, etc.  Some nurseries may produce indexed or “crown gall free” plants.  The California Clean Plant Network is trying to clean these diseases from stock. When purchasing plants, it might be good to ask others for nursery recommendations.  We have had one case where identical rootstock/scion combinations were purchased from two different nurseries and planted at the same time.  One nursery’s plants were inundated with crown gall, whereas the other (same block) was absolutely clean – same environment and management techniques.

Symptomatic plants can produce brilliant red leaves. Galls are at the graft union or crown.