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Sudden Oak Death Discovered at Nursery in Oregon's Clackamas County
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Sudden Oak Death Discovered at Nursery in Oregon's Clackamas County

May 12, 2003

Contact: Cam Sivesind at (503) 682-5089 or (800) 342-6401.

Incident is called isolated, and source of disease appears to be from outside of the state's borders.

Today the Oregon Department of Agriculture confirmed a finding of Phytophthora ramorum, a fungus that causes a plant disease popularly referred to as Sudden Oak Death (SOD) syndrome, at a small container nursery in rural Clackamas County. ODA is actively investigating the source of this isolated incident of P. ramormum.

Initial evidence suggests the appearance of P. ramorum in the Clackamas County nursery originated with plants imported from Europe. The affected plants are Viburnum bodnantense and Pieris formosa, also known as Arrow wood and Andromeda. In Europe P. ramorum has more often been found in commercial nurseries than it has in natural settings, unlike California where the plant disease doesn't appear to occur in commercial nurseries, with one exception reported, and has spread by natural causes in public parks and other outdoor settings.

Fortunately, Oregon's white oak (also known as Oregon oak) is the oak tree most common to the state and tests show this species of oak is not susceptible to P. ramorum. This is also the case in Europe, where white oak species are more common than the kind of oak species found in California.

"The Oregon Department of Agriculture has done an outstanding job to respond quickly and aggressively to this recent finding of P. ramorum," said John Aguirre, executive director for the OAN. "It bodes well that ODA's surveillance and inspection picked up the disease, because the only way we can prevent its spread is to look for it and to respond quickly if and when it is found."

ODA officials have quarantined the nursery and, with the help of the cooperative nursery manager, the affected plant material has been destroyed. Adjacent properties are being surveyed, and the ODA is moving up its scheduled 2003 survey of Oregon nurseries. ODA's surveys of nurseries each of the past two years -- which in 2002 alone included collecting and testing nearly 4,000 plant samples from host plants at 81 nurseries and 17 Christmas tree farms -- found no instances of P. ramorum.

Clackamas County leads all other counties in Oregon in the production of nursery and greenhouse plant material, which is the state's biggest agricultural crop with more than $680 million in sales in 2001. Clackamas county nursery and greenhouse growers sold $155 million of product in 2001. Until now, SOD in Oregon had been confined to a small area of Curry County in the southwestern corner of the state and 12 counties in California, with the heaviest outbreaks centered around the San Francisco bay area.

"The initial evidence points toward Europe as the source of infected plant material, said Mark Krautmann, OAN president and co-owner of Heritage Seedlings Inc., a Salem-area nursery. "As a nursery grower, I urge anyone bringing in European plant material on USDA's host plant list to make certain it's purchased from a reputable dealer who is certified free of P. ramorum, and to contact your local agriculture inspector to have those plants inspected."

USDA reported in February 2003 that 273 sites in Europe tested positive for the presence of this plant pathogen, with the majority of those sites being commercial nurseries.

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 -- with more than 20 known susceptible species. 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.

"We've dreaded the discovery of the pathogen at an Oregon nursery, but we are thankful it appears contained and isolated, and that the source of the disease seems have come from outside of the state," Aguirre said. "Fortunately, ODA and OAN have a strong cooperative relationship so I can honestly say this is as good as bad news can get."

For more information, log on to the ODA Web site at, the USDA Web site at or the California Oak Mortality Task Force Web site at

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 2001 sales of $680 million.

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