Symptoms and Signs
Foliar symptoms typical of a root and/or crown rot pathogen are lack of vigor, small leaves, poor terminal growth, open canopy, and yield reduction. Galls are the most obvious symptoms of crown gall; however, they are not always visible. Galls range in size from nearly microscopic to 12 inches or more in diameter.
Comments on the Disease
Agrobacterium tumefaciens is primarily disseminated by infected plant material or in soil during cultivation. It enters the plant only through wounds, most commonly on roots or the crown. The roots of young vines may be injured during transplanting, while older vines can be injured by common cultural practices that use machinery. Additionally, vines may be wounded by frost, herbicide, pruning, removal of suckers, or they may develop growth cracks.
Control of crown gall is best achieved by avoiding injury to vines. A minimum of handling during transplanting and care during cultural practices using machinery should greatly reduce the risk of wounding. Galltrol is registered as a preventative preplant dip. Its effectiveness will depend on whether there are susceptible or resistant A. tumefaciens strains at the planting site. Existing galls can be surgically removed.