Rose -- Crown Gall
See Also: Cherry -- Crown Gall

Cause: The bacterium Agrobacterium tumefaciens enters plants through wounds,
either natural or caused by pruning, grafting, mechanical injury from
cultivation, heaving of frozen soils, chewing insects, or the emergence of
lateral roots. After the bacterium enters a wound, a small piece of its DNA
is transferred into the plant's DNA. The foreign DNA transforms normal plant
cells in the wounded area into tumor cells. Once transformed, tumor cells
proliferate automatically. The result is a gall, a disorganized mass of
hyperplastic and hypertophic tissue.

Pruning tools that cut through galls can become contaminated with the
bacteria and spread them to cut surfaces of subsequently pruned plants.
Galls breaking down in soil release bacteria which can be transported by
moving soil or water. In the absence of plant roots, bacterial populations
gradually decrease; however, the pathogen may survive in soil at least 2
years.

Symptoms: Galls are often at or just below the soil surface in the basal or
crown region. They may frequently be on roots, less frequently on aerial
plant parts. Galls are usually rounded with a rough, irregular surface. They
first appear as small protuberances on the plant surface. Young, actively
developing galls are light green or nearly white, and the tissue is soft. As
they age, galls become dark and woody. Outer portions can slough off with
age. Sometimes galls have a rather smooth surface, which makes it difficult
to distinguish between gall and callus growth, especially if the gall is at
the plant base or at the graft or bud union. Plants can be stunted and have
reduced vigor, poor foliage, and fewer blossoms. A single gall at the
plant's base may be more detrimental than several galls on canes and roots.
Symptoms may not develop for over a year if infection occurs when
temperatures are below 59°F.

Cultural control:

Use only disease-free nursery stock. Inspect new plants; do not plant any
rose that has galls.
Avoid wounding plants, especially at planting. If root pruning at planting,
soak in biocontrol agent listed below.
Use plants with resistant rootstocks. Rootstocks differ widely in
susceptibility.
Prune off any galls on aerial parts of the plant.
Disinfect pruning shears frequently. Clean shears and long soak times
improve the disinfectant's efficacy.
Remove and destroy badly affected plants.
Preplant soil solarization has been effective for cherry nursery stock in
western Oregon. Place clear plastic on rototilled ground, irrigated to near
field capacity, from mid-July to mid-September. More effective on sandy loam
soil. The technique may help after removing diseased plants from a bed in
which roses will be planted again.

Chemical control:

Gallex (ready to use) painted on very young galls to reduce further
development. Galls may return the following year or, if treated late, may
continue to develop. Tissue surrounding the gall may be injured, especially
on younger plants. Prepare the surface by removing soil from around the
galled area, and allow the area to dry before application.

Ferti-lome Fire Blight Spray (streptomycin) at 0.5 Tbsp/2.5 gal water. Soak
root system and cut surfaces for 15 min in this solution. This works better
as a wound protectant than as a cure. Cutting away galls, as label directs,
may help, but all galled tissue must be removed. Getting a new, disease-free
plant will work better. Foliar sprays, as label directs, are not
recommended.

Biological control: Agrobacterium radiobacter strain 84 has been used
successfully with roses in Australia, New Zealand, and Spain but has not
been effective in limited trials in the United States. Strain K 84 is
preventive only. Latent infections (symptomless) and existing galls are not
controlled. A suspension of strain 84 may be used as a soak or spray.
Thoroughly cover grafting wood, roots, and crown. Spray to runoff. To be
effective, it must be applied a few hours after wounding. 12-hr reentry.

Galltrol.
Nogall is a genetically modified strain of K84 that will help reduce the
potential for development of resistant crown gall bacteria. 4-hr reentry.

Content edited by: Jay W. Pscheidt on January 1, 2003

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This is from our University's Extension Plant Disease Control.
I thought you would find some of it interesting and helpful if
for no other reason than to arm yourself with knowledge.

http://plant-disease.ippc.orst.edu/d...m?RecordID=984

in case you want to look at the photos ;)

Allegra