Disease name: Crown gall
Pathogen name: Agrobacterium tumefaciens (bacterium)
Hosts: Crown gall is caused by a soil-borne bacterium (Agrobacterium tumefaciens). Numerous plants can be host to this disease, although relatively few species sustain significant damage. Common hosts that are seriously affected include roses (Rosa spp.), wintercreeper euonymus (Euonymus fortunei), forsythia (Forsythia spp.), poplar (Populus spp.), and willow (Salix spp.).
Symptoms
Rough textured galls form on roots and stems, especially near the base of the plant. Galls on poplars and willows can occur in upper branches.
As the galls continue to enlarge, they can girdle stems, cutting off the water supply and disfiguring woody stems.
Young plants with large or numerous galls tend to be stunted and predisposed to drought damage or winter injury.
Disease Cycle
The bacterium that causes crown gall lives in the soil. It can enter the host plant through wounds in the roots or base of the plant.
Once inside the host plant, the bacterium inserts part of its DNA into the DNA of the plant. This causes the cells of the plant to divide rapidly and form the gall. This process can occur within two to four weeks of the infection.
The galls are often irregular in shape due to secondary galls that form alongside the original gall.
As the season progresses, galls can start to decay. As the gall decays, bacteria is spread into the soil.
The bacteria can survive in the soil for several years. It can be moved on contaminated soil, as well as on the roots of plants that are already infected.
Management
Cultural Management
Inspect newly purchased plants for any signs of gall on the roots and lower stems.
Avoid wounding plants during the planting process.
Do not plant host plants in areas known to be contaminated by crown gall.
Remove infected plants to avoid further spread of the bacteria.
Do not compost infected plants.
Resistant Species
Plants that are resistant to crown gall include:
- Grasses
- Conifers
- Beech (Fagus)
- Birch (Betula)
- Boxwood (Buxus)
- Deutzia (Deutzia)
- Ginkgo (Ginkgo)
- Hornbeam (Carpinus)
- Linden (Tilia)
- Magnolia (Magnolia)
- Redbud (Cercis)
- Serviceberry (Amelanchier)
- Smoke tree (Cotinus)
- Tulip tree (Liriodendron)
- Yellowwood (Cladrastis)
- Yew (Taxus)
- Zelkova (Zelkova)
Chemical Management
There is no chemical management available for this disease.
The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.
For current pesticide recommendations, contact The Morton Arboretum Plant Clinic at 630-719-2424 or plantclinic@mortonarb.org.