This plant disease is caused by a soil-inhabiting bacterium (Agrobacterium tumefaciens) that infects many ornamentals and fruit trees in the garden. The bacteria are spread with the soil and contaminated pruning tools, and are often brought to a garden initially on the stems or roots of an infected plant. The bacteria enter the plant through wounds in the roots or the stem. They produce a compound that stimulates rapid cell growth in the plant, causing gall formation on the roots, crown, and sometimes the branches. The galls disrupt the flow of water and nutrients up the roots and stems, weakening and stunting the top of the plant. Galls do not usually cause the death of the plant. For more information about crown gall, see Crown Gall.
Crown gall cannot be eliminated from a plant. However, an infected plant may survive for many years. To improve its appearance, prune out and destroy galled stems. Sterilize pruning shears with rubbing alcohol after each cut. Destroy severely infected plants. The bacteria will remain in the soil for 2 to 3 years. If you wish to replace the infected roses soon, select other plants that are resistant to crown gall (for a list, see Trees and Shrubs Resistant to Crown Gall).
Plant Care for Rosa