CORVALLIS, Ore. – A newly updated publication outlines how the public can help stop the spread of a disease that has killed more than a million oak and tanoak trees in 14 coastal counties in California and thousands of tanoaks in Curry County, Ore.
"Stop the Spread of Sudden Oak Death" (EC1608) is available for free online.
Sudden Oak Death is the common name for the disease caused by a pathogen, Phytophthora ramorum.
"No one knows where the pathogen came from or how it was introduced in Oregon," said Dave Shaw, an Oregon State University plant pathologist. He and Ellen Goheen, plant pathologist with the U.S. Forest Service, are authors of the publication.
Other hosts for the disease are California black oak, Douglas-fir, grand fir, coast redwood, Pacific madrone, Pacific rhododendron, evergreen huckleberry, and many other tree and shrub species common in Oregon and Washington forests. The disease also causes branch and shoot dieback and leaf spotting on a large number of woodland and nursery plant species.
Hosts in the nursery trade include varieties of rhododendron, camellia and Pieris. A complete host list is on the USDA-APHIS website.
P. ramorum spreads naturally when mist and rain move spores within forest canopies – from treetops to stems and shrubs below, or across landscapes from treetop to treetop.
"Humans help spread the disease when they transport infected plants, plant parts or infested soil," Shaw said. "State and federal inspectors survey forests and nurseries in Oregon regularly to detect the disease. Infected plants and adjacent host plants are destroyed to slow spread of the disease."
State and federal quarantine regulations minimize the risk of new infections and prevent human-assisted spread. Complete texts of these regulations (ORS 603-052-1230 and 7 CFR 301.92) are on the Oregon Department of Agriculture and the U.S. Department of Agriculture websites.
People can spread Phytophthora ramorum across long distances by moving infected plants either purchased at a nursery or collected in the wild, or by moving infected wood, leaves, stems or soil.
The authors say there are things persons living, working, or visiting in the quarantined portion (map printed in publication) of Oregon's Curry County can do to help stop the spread. These include:
- Become familiar with the most recent regulations on Sudden Oak Death (websites in publication).
- Do not collect and remove host plants or plant parts from the forest.
- Do not collect or remove soil.
- Stay on established trails and respect trail closures.
- Before leaving infested areas, clean and disinfect equipment such as saws, shovels and pruning equipment you used in infested areas; wash soil off tires, wheel wells and the undercarriage of your vehicle; clean soil off shoes, mountain bikes, horse hooves and pet paws.
- For best protection, use a 10-percent bleach solution for cleaning.
- Buy healthy plants from reputable nurseries.
For more information, contact the OSU Extension foresters in local county offices, or a forester working with a state or federal agency.
OSU Extension, Curry County, 29390 Ellensburg (Hwy 101), Gold Beach, OR 97444, 541-247-6672 or 1-800-356-3986