Sudden Oak Death

Sudden Oak Death

Pathogen / Invasive (first found in California in 1995)

Phytophthora ramorum is a water mold pathogen that causes Sudden Oak Death (SOD), Ramorum Leaf Blight, Ramorum Dieback, and Phytophthora Canker Diseases. SOD was first detected in Marin County, CA in 1995, and it was recognized as killing trees in Oregon in 2001. The SOD pathogen affects a wide variety of trees, shrubs, and plants and there is no known cure. The pathogen has killed millions of tanoak and coast live oak trees along the central CA coast into Southern OR. It also infects rhododendron, camellia, and other common horticultural nursery plants.


More than 100 plant species can be infected by P. ramorum or facilitate its spread. The host list includes: hardwoods (e.g. coast live oak), softwoods (e.g. Douglas-fir), and landscape plants (e.g. camellia and rhododendron).

Management activities:

Multiple organizations, including USDA-APHIS and the Oregon Department of Forestry, are working to stop the spread of P. ramorum through regulations and public outreach programs. Agencies work to limit human-assisted spread of P. ramorum by inspecting nurseries for infected plants and plant material. APHIS has also enacted strict regulations in 15 counties along the California and Oregon coastline because P. ramorum causes significant disease in those forest environments.