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Oregon Keeps Sudden Oak Death Contained, Despite Expanding List of Host Plants
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Oregon Keeps Sudden Oak Death Contained, Despite Expanding List of Host Plants

September 4, 2002

Contact: John Aguirre at (503) 682-5089 or (800) 342-6401.

Researchers find that Douglas firs and California's coast redwoods are another species affected by deadly disease

California researchers reported findings today that the fungus, Phytophthora ramorum, known to cause Sudden Oak Death (SOD) in oak trees and in other ecologically and commercially significant plant species, has been found to affect Douglas firs and California's coast redwoods. As a result of these findings, the U.S. Department of Agriculture will include these two tree species on its list of host plants regulated under its SOD quarantine.

Currently, SOD affects 12 California counties and a small portion of one southwest Oregon county, Curry County, located along the California border. SOD in Oregon remains well contained within a 9-square-mile quarantine zone in Curry County near the town of Brookings. The Oregon Department of Agriculture and the Oregon Department of Forestry have conducted extensive surveillance from the air and on the ground in search of SOD infested sites in Oregon. An intensive and aggressive eradication program has and will continue to reduce economic and ecological impacts of the disease. In addition, ODA officials have collected and tested thousands of plant samples from Oregon nurseries and greenhouses, and all have been found free of the fungus that causes SOD.

"Government and industry are working well together to prevent the spread of Sudden Oak Death in Oregon," said John Aguirre, OAN executive director. "Presently the disease is confined to a few acres within Curry County. Consequently we believe it is possible to eradicate Sudden Oak Death from within the state."

"Nursery industry operators are on a high state of alert for the appearance of Sudden Oak Death," said Mark Krautmann, owner of Heritage Seedlings Inc., a Salem-based nursery operation. "We intend to do whatever is necessary as an industry to keep this plant disease limited to a very small quarantine zone well south of major nursery production areas, and hopefully we will eliminate the disease from Oregon entirely."

SOD was discovered to affect Douglas firs and coast redwoods by two researchers -- Dave Rizzo, an associate professor at the University of California at Davis, and Matteo Garbelotto, UC Berkeley cooperative extension forest pathology specialist and adjunct professor of plant pathology. Both researchers have spent considerable time studying P. ramorum and are members of the California Oak Mortality Task Force, a non-profit organization created under the California Forest Pest Council in August 2000. The task force has brought together public agencies, other non-profit organizations and private interests to address the issue of elevated levels of oak mortality and is working to implement a comprehensive and unified approach for research, management, education and public policy.

The researchers isolated living cultures of P. ramorum from the branches and needles of coast redwood and Douglas fir saplings that has shown symptoms of infection. They first announced the discovery of the fungal DNA in the trees earlier this year but could not confirm that the pathogen was causing infection until living cultures were successfully grown from the field samples. The test results will be published online in October in the journal Plant Disease.

Sudden Oak Death is the popularized name for a plant disease caused by Phytophthora ramorum, a fungus-like organism affecting susceptible trees and woody shrubs. Phytophthora species are water molds with approximately 60 different species recognized worldwide. Researchers continue to expand the list of plant species susceptible to P. ramorum -- now at 17 know species with the addition of the coast redwood and Douglas fir. The disease can produce rapid decline in tanoak and in susceptible species of oak, characterized by bleeding cankers on the lower trunk of trees. These cankers produce a sticky, very reddish substance. Mortality appears less likely with other plant species. Damage from SOD in rhododendron, for example, typically involves leaf spotting, cankers on small branches and stems, and/or stem dieback.

For more information, log on to the California Oak Mortality Task Force web site at, or visit the Sudden Oak Death information pages on this site.

The Oregon Association of Nurseries, based in Wilsonville, represents more than 1,600 wholesale growers, retailers, landscapers and suppliers. Oregon's ornamental horticulture industry is the state's largest agricultural commodity, with 2002 sales of $727 million.

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