Crown Gall Control



Crown Gall is a common disease of many woody shrubs and some herbaceous plants. It is caused by the bacterium Agrobacterium tumefaciens which can infect 140 genera in over 90 families of plants. It is especially common in the rose family. The Agrobacteria have been extensively studied over the last 80 years. They are useful today in the genetic engineering of plants because of their ability to integrate parts of their own DNA into a plant’s genome. In nature this ability allows the transformation of normal plant cells into tumor cells.
HOST PLANTS: Common in stone fruits such as cherries and plums but also observed in apricots and peaches.

SYMPTOMS: As the name implies, galls tend to form on the stem at the soil line. However, galls may also form on the roots or on above ground stems and twigs. The galls are rough, hard and woody when older; young galls may be smooth and somewhat spongy. Unlike insect galls, these galls are solid throughout. They vary in size from very small to over an inch in diameter. Infected plants may be stunted and lack vigor because of the disrupted flow of water and nutrients from the roots.

FAVORED ENVIRONMENT: 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.

CROWN GALL 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. There is no commercial cure for crown gall.

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