Sudden oak death, caused by the non-native pathogen Phytophthora ramorum, continues to threaten Oregon’s forests and rural communities. The disease has killed hundreds of thousands of tanoak trees in Curry County and contributes to up to 80% tanoak mortality in infected areas. As of late 2023, the Oregon Department of Agriculture expanded the state quarantine zone from 264 to 519 square miles — doubling the regulated area to contain the spread.
Extension’s research-based outreach, community partnerships and early detection programs are helping to protect forest health and support informed stewardship.
The disease spreads naturally up to 5 miles per year and can also travel through contaminated soil, plant debris and human activity. Three lineages of P. ramorum have been introduced to Oregon’s forests. The most recent, discovered in 2021 in Port Orford, raised concern because it appeared far from previously infested sites. To date, over 8,200 acres have been treated in Oregon, with more than $35 million spent on eradication.
Oregon State University Extension Service is helping communities respond through education, outreach and early detection. The sudden oak death outreach program trains landowners, natural resource professionals and residents to recognize symptoms, understand treatment and comply with regulations. Local workshops, webinars and fact sheets help stakeholders make informed decisions and slow the spread.
In 2019, OSU Extension, the Oregon sudden oak death program, and the LeBoldus Lab at OSU launched a community science initiative. Landowners in Curry County are trained to place bait stations — buckets of water with susceptible leaves — under tanoak trees and in streams. These are analyzed for the presence of P. ramorum spores before visible symptoms appear. From 2019 to 2022, 52 bait stations and seven stream sites were monitored by community scientists.
To reduce risk in nurseries and restoration projects, OSU Extension partnered with Washington State University to publish Preventing Phytophthora Infestations in Restoration Nurseries, which outlines sanitation, drainage and monitoring best practices. In 2024, Extension hosted Healthy Nurseries, Resilient Plants, a hands-on workshop led by plant pathologist Luisa Santamaria and forester Norma Kline. Attendees learned how to recognize symptoms, implement sanitation protocols and prevent infestations. Post-event surveys showed increased knowledge and intention to improve practices.
These efforts are supported by OSU Extension's Sudden Oak Death: Prevention, Recognition, Restoration, which is written for homeowners, landowners and conservation groups.
With more than 811 square miles of forest still at risk in Oregon, Extension’s research-based outreach, community partnerships and early detection programs are helping to protect forest health and support informed stewardship.
