Causal agent is a bacterium called Agrobacterium tumefaciens. This bacterium attacks a broad spectrum of woody and herbaceous plants in more than one hundred and forty genera. Euonymous, rose, maple, willow and brambles are commonly infected plants in Illinois.
This bacterium causes the host plant to produce galls at the crown, on roots, or on branches. Since a bacterium is usually a weak pathogen, entry is through a natural opening (for example - a lenticel) or a fresh wound that is less than twenty-four hours old on the crown, the roots, or the branches. Often the galls are found near the soil line, at a graft union, or bud union. On willow and populars, the galls may be found on branches as much as twenty to forty 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.
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 a 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 more. Plants may be stunted, discolored, and die back. Young plants eventually wilt and die while older plants survive in a weakened condition.
Carefully dig up and destroy young infected plants. Do not replant with a susceptible plant in the same site for five or more years. Plant only certified clean stock. Avoid injury or wounding the plant. Sterilize pruning tools between plants. Use rubbing alcohol straight out of the bottle (allow tools to sit in alcohol for a minute or more or flame the alcohol off the tool). Chlorine bleach may also be used at a twenty-five percent solution. Control insects as necessary.
Written by James Schuster, Retired Extension Educator, Horticulture & Plant Pathology, and reviewed by Nancy Pataky, Retired Extension Specialist, Plant Pathology, Department of Crop Sciences University of Illinois at Urbana-Champaign.
Filed under plants: Deciduous Trees & Shrubs
Filed under problems: Bacterial Disease