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University
of Rhode Island GreenShare Factsheets
Crown
Gall on Ornamental Plants Agrobacterium
tumerofasciens
Crown
gall, caused by the soil-borne bacterium Agrobacterium tumerofasciens,
is characterized by the growth of galls on roots or stems. Although
found on more than 600 plant species in over 90 families, the disease
is of economic importance on relatively few ornamental plants. Some
commonly affected ornamentals include rose, Prunus spp. (flowering
cherry, flowering almond and ornamental plum), willow and Euonymus
(especially wintercreeper).
Crown gall is a tumorous growth of plant tissue up to several inches
or more in diameter. Galls form on stems or more commonly on roots,
especially at the stem-root interface. Young galls are light-colored
and smooth. Older galls become discolored, hard and woody, and eventually
crack, decay and slough off. The severity of this disease depends
on the size, number and location of galls, as well as the susceptiblility
and age of the plant. Infected plants tend to exhibit a general
decline in vigor, although crown gall may have little noticeable
effect on older plants. Galls which develop on the crown of young
plants have the greatest adverse effect, causing stunting and reduced
flower display. Infected plants tend to be more susceptible to drought,
winter injury and Armillaria root rot. Bacteria
can survive in soil for more than 10 years. Crown gall bacteria
may be spread through contact with soil, water or contaminated tools.
Bacteria require fresh wounds to enter plant tissue. These may result
from feeding by insects and nematodes, pruning, transplanting and
frost heaves. Upon entry into plant tissue, the bacterium transfers
its genetic information to plant cells, resulting in rapid, localized
growth of plant tissue. Bacteria can move in plant tissues, causing
secondary galls to form around the affected area. • Avoid
wounding plants when planting, transplanting, and cultivating.
• Clean tools routinely while pruning or grafting.
• Soils where infected plants have grown may support high populations
of crown gall bacteria on root fragments left after removal of
these plants. Remove surrounding soil when digging out infected plants.
• Select resistant plants as replacements such as bald cypress,
beech, boxwood, deutzia, gingko, goldenrain tree, holly, hornbeam,
larch, linden, magnolia, pine, serviceberry, spruce, tuliptree,
yellow wood, Japanese yew and zelkova.
Adapted
from Ohio State University Extension, 1999;
Diseases of Ornamentals, BP-33, Purdue University Cooperative Extension
Service, 1999
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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