Frederick County Master Gardener Program
Oak Death (SOD) is a tree and plant disease which
mostly affects Oaks. It began to appear in California
and in Europe in 1995. SOD has spread through 16
counties in California, even infecting redwood trees.
SOD was first discovered in Oregon in 2001. Oregon
recently reported the good news that the disease has
been contained on 88 acres of land. Currently there
are around 39 states affected by this disease. Its
origins are not known. SOD is made up of three parts:
the first is a fungus pathogen called Phytophthora
ramorum; it destroys the vascular system of the tree.
The second part is actually three beetles: two
different types of Oak ambrosia beetles and one Oak
bark beetle. They weaken the health of the tree. And
the third is another fungus called Hypoxylon
thouarsianum; this decays the tree.
It can spread from mud on
peoples' shoes, bike tires, cars, and forest animals.
Even from irrigation water from infected streams. The
most common way it is spread though, is through rain
splashes from other infected trees.
Why should we worry about SOD
here in Maryland? Some of the nurseries from
California that are importing plants to Maryland may
have been infected by SOD. There are over 60 different
species of plants that are affected by SOD. Maryland
has many possible hosts, including Douglas fir, oak,
western starflower, rhododendron, lilac, mountain
laurel, camellia, and viburnum. Because Maryland has
so many hosts for this disease, SOD could kill
thousands of our trees and plants, devastating our
forests, and changing the landscape. However, only
plants bought and planted within the last two years
could be hosts.
For trees, symptoms of
bleeding or oozing can occur on the outer bark-usually
on the lower 6 feet of the trunk. Cankers in the inner
bark could occur as well, surrounded by a black line.
For other plants, there could be leaf spots, leaf
drop, tip dieback and stem lesions. These are symptoms
of many other diseases, so unless you have bought and
planted one of the host plants within the last two
years, it is unlikely that your plant has SOD.
What treatments are there for
SOD? One way is to use chemicals on trees and plants,
which is helping slow down the disease; California
uses this method. Oregon's method is to cut and burn
around the perimeter where plants and trees are
affected, stopping the disease from spreading
elsewhere. Since, (in Maryland) very few infected
plants have been reported, Maryland is using
prevention as a control. To prevent the disease from
spreading throughout the country, all nursery plants
known to harbor the disease in California and Oregon
are inspected before being shipped to other states.
Some nurseries have been quarantined. Any plants that
are found infected will be destroyed.
In May, 2006, the House of
Representatives passed an agricultural bill allocating
$7.7 million for research targeting Sudden Oak Death.
What should I do if I suspect
I have an infected plant or tree?
Some options for getting
treatment would be to contact the Maryland Home and
Garden Information Center at 1-800-342-2507, 8 A.M. -
1 P.M. M-F, or www.hgic.umd.edu or the Maryland
Department of Agriculture at www.mda.state.md.us