Two strains of pathogen

Two strains of pathogen found

The American strain of sudden oak death was found for the first time in 1995 in Mill Valley, California. Since then, it has been detected in 17 California counties. And in 2001, it was found in Curry County, Oregon near the California border.

The disease has killed thousands of oak and tanoak trees found in California and Oregon. Other plants common to the Pacific Northwest are susceptible to the disease, but are not likely to die.

Since May 2003, the European strain of sudden oak death has been detected in nurseries in Oregon, Washington and British Columbia, Canada, although most infected plants are by the American strain. There is no evidence that either strain has moved beyond the nursery environment.

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The origin of sudden oak death is unknown

Plant pathologists do not know where the pathogen originated, but the disease is spread naturally and artificially. In nature, the pathogen is spread through the movement of water in the form of rain, mist, dew and runoff. Humans spread the disease through the movement of infected nursery stock and possibly with firewood and soil on the bottoms of shoes and boots. (Although viable spores have been detected on boots there is no evidence that the pathogen is spread this way.)

No pesticide to control sudden oak death

There is no pesticide registered by the U.S. Environmental Protection Agency that will eradicate the organism that causes sudden oak death. The only way to stop the disease is to cut down and burn infected plants or trees.