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Crown Gall

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Thursday, January 11, 2007

Question:
I have strange, large circular growths or swellings on the stems of my euonymus plant. The swelling does not appear to be killing the plant
yet. What should I do ? R.K. Westfield, NJ.

Answer:
The growth or your euonymus is crown gall. It is a bacterial disease caused by Agrobacterium tumefaciens. The disease orgasnism has a wide host range and can attack more than 600 plant species. In ornamentals, the disease is mainly a problem of plants in the Prunus family but can infect others as well. The disease can be found on many ornamental plants including rose, euonymus, lilac, hibiscus, privet, viburnum, willow, flowering cherry and peach.

The crown gall disease causes galls on plant stems and roots. The
galls are often found near the soil and can range from pea size up to several inches or more in diameter. On some trees, the galls can be very large and can be found higher on the tree. Galls may first appear smooth and later become woody and form cracks on the swelled areas.

Galls can interfere with the transport of water and nutrients through the plant and sometimes lead to decline or death. However, more often the disease is mainly an aesthetic problem and the plant will survive and even thrive in spite of the disease.
The location and size of the galls will determine the impact on infected plants.

The bacteria that cause this disease can be found naturally in some
soils and can persist for years in infected soils. When susceptible
plant roots or stems of plants are wounded, the bacterial can enter and
induce gall formation. Wounds can occur from pruning or digging and
cutting into plant roots. Soil insects can also contribute to the problem.

Unfortunately, there are no effective chemical controls for crown gall.
In order to reduce crown gall in your landscape, you could try the
following: avoid unnecessary pruning or wounding of susceptible plants, remove and destroy infected plants, plant crown gall resistant plants in gall infested areas, and avoid purchasing susceptible plants with strange growths on stems.

In many cases, mature plants can survive and thrive in spite of the crown gall disease.
Do not attempt to prune galls on main branches on trees or shrubs.
Galls on secondary branches are sometimes pruned out successfully. Be sure to disinfect pruning tools with a 20% bleach solution or you could spread the bacteria to other susceptible plants.

There is an effective biological control agent for crown gall called Agrobacterium radiobacter, sold as Galltrol A, Nogall or Diegall. Crown gall susceptible plants can dipped in solutions of this beneficial bacteria before planting. The biological control can help to prevent galls to susceptible plant roots but sanitation is still critical for above ground portions of the plant..

For more information on crown gall and list of susceptible and resistant plant log on to onto www.ifplantscouldtalk.rutgers.edu or visit our
main Rutgers Cooperative Extension web site at www.rce.rutgers.edu.


Bill Hlubik is a Professor and Agricultural and Resource Management Agent for Rutgers Cooperative Extension- The New Jersey Agricultural Experiment Station, Rutgers University.

Bill is also a host of the "If Plants Could Talk" television series on NJN Public Television.