This plant disease is caused by a soil-inhabiting bacterium (Agrobacterium tumefaciens) that infects many ornamentals, fruits, and vegetables in the garden. The bacteria are spread in the soil, and are often brought to a garden initially on the roots of an infected plant. The bacteria enter the tree through wounds in the roots or the base of the trunk (the crown). They produce a substance that stimulates rapid cell growth in the plant, causing gall formation. The galls disrupt the flow of water and nutrients up the roots and trunk, weakening and stunting the top growth. They do not usually cause the tree to die. For more information about crown gall, see Crown Gall.
Infected trees cannot be cured. However, they often survive for many years. Although the disease cannot be eliminated from the tree, individual galls can be removed by professionals. If you wish to remove galls from valued trees, consult a professional horticulturist or landscape contractor. The bacteria will remain in the soil for as long as 3 years after an infected tree has been removed. Replant with one of the resistant trees from the list in Trees and Shrubs Resistant to Crown Gall.
