Sudden Oak Death
Sudden oak death (SOD) is a fungal disease that causes a rapid decline
and death of oaks. The name is a bit misleading because it also occurs
on other tree and shrub species, 17 in all. Symptoms vary from leaf
spots to twig blight to trunk cankers. Roots do not show symptoms.
The causal fungus of SOD is Phytophthora ramorum. At present,
the disease has been identified only in ten California counties and
one Oregon county. Oaks affected are tan oak, coast live oak and California
black oak, none of which grows in Illinois. Research has shown that
red and pin oaks are susceptible when artificially inoculated. In addition,
some other plants grown in Illinois can serve as hosts, including rhododendron,
azalea and Douglas fir. Obviously, there is great concern that the disease
might move on these plants to other areas of the country.
SOD causes rapid decline of oaks, usually resulting in death in one
to three years. On oak, the disease causes a bleeding canker on the
stems or trunk. These cankers ooze a black or reddish fluid. The wood
under them has black zone lines evident when bark is removed. Once crown
dieback begins, the leaves turn brown in a few weeks.
Because of the concern of movement of this disease out of California
and Oregon, USDA began regulating the shipment of all host plants in
February of 2002. The animal and plant health inspection service (APHIS)
has surveys planned for some of the southeastern states (GA, SC,NC,
TN and VA) where the disease is most likely to take hold. These surveys
are slated for the spring of 2003. Oklahoma plant pathologists have
already initiated some nursery surveys and have not yet found the disease.
There is a tremendous amount of information available on this disease
on the Internet. A good source to start with is the USDA “Sudden
Oak Death Pest Alert,” NA-PR-02-02, at
http://www.na.fs.fed.us/spfo/pubs/pest_al/sodeast/sodeast.htm
November-December
2002
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