Crown Gall

Agrobacterium tumefaciens causes the host plant to produce galls at the crown, on roots, or on branches. The gall is a light tan color at first but turns brown to black with age. Galls are soft and round when they first form but later develop an irregular, rough, and corky surface with a woody interior. The size of the gall varies from the diameter of a pea to a foot or larger. Infected plants may be stunted, discolored, and die back. Young plants eventually wilt and die while older plants survive in a weakened condition.

Often the galls are found near the soil line, at a graft union, or bud union. On willow, populars, and other trees, the galls may be found on branches as much as20 to 40 or more feet above the ground. This disease may be a localized infection or it may be systemic on some plants such as the brambles and grapes.