Symptoms: A common plant disease caused by the bacterium, Agrobacterium tumefaciens, crown gall occurs on many woody shrubs and some herbaceous plants, including grapes, raspberries, stone fruits and roses.
Crown Gall can be identified by the large distorted growths that appear between the root and trunk of a plant, just above soil level. Plants with several galls may be unable to move water and nutrients up the trunk and become weakened, stunted and unproductive. Young plants can be killed by developing gall tissue.
The bacteria responsible for crown gall can persist in the soil for many years and are released when galls become saturated with moisture or as older galls decompose. Susceptible plants are infected through fresh wounds or abrasions, many of which are a result of pruning, freeze injury, soil insects, cultivation and other factors that may damage plants. Nursery stock is often infected through grafting and budding scars.
Control: Select resistant cultivars when possible and purchase plants from a reputable nursery. Do not buy plants that shows signs of swelling or galling. When caring for susceptible plants, avoid injury or pruning wounds that may come in contact with the soil. Do not use string trimmers around the base of trees and keep your garden tools clean. Provide winter protection so bark won’t crack. In many cases, existing galls can be removed with a sharp knife. Destroy the infected plant tissue and treat the wound with tree surgeons paint. If the plant does not recover, remove and destroy it.
Tip: To control crown gall in roses, remove the infested plant and prune out gall tissue. Soak the entire root system and cut surfaces for 15 minutes in a solution of 2 level Tbsp of Fire Blight Spray per 2-1/2 gallons of water. Replant in healthy soil, and apply 1/2 Tbsp per 2-1/2 gallons of water as a foliar spray at weekly intervals.
Photo Credit: The University of Georgia College of Agricultural and Environmental Sciences