PORT ORFORD, Ore. – Forest Pathologist Sarah Navarro with the USDA Forest Service said work is expected to begin soon to cut down and burn tanoak trees near Port Orford found to be infected with the pathogen that causes sudden oak death.
An Oregon State University researcher driving along Highway 101 this spring was the first person to notice dying tanoaks about a mile outside Port Orford. Tests showed those trees were infected with the NA2 strain of Phytophthora ramorum, a water mold that causes the plant disease. This was the first time that strain had been found in the wild in Oregon.
Navarro said the full extent of the area to be treated won’t be known until test results from tanoak trees sampled at the edges are completed. “Right now, though, we know the area needing treatment is at least 388 acres. That makes this the largest infestation we’ve seen outside the quarantine area set up to slow the spread of sudden oak death.”
Navarro said the goal of treatment is to eradicate the pathogen at this site, which is 21 miles north of the quarantine zone. “Contract crews overseen by the Oregon Department of Forestry will cut infested tanoak trees, pile them and later burn them. ODF is also checking notifications about any forestry operations to make sure tanoak trees are not being removed from the area.”
Sudden oak death is especially deadly to tan oaks, a broadleaf evergreen tree that naturally grows only in northern California and southwest Oregon. “The pathogen can infect many plants, including a wide range of native shrubs and trees, but it appears to only produce on tanoaks the spores that can spread the infection in the wind or rain. This is why we target tanoaks for removal.”
Navarro said the large size of the infected area suggests the pathogen has been present there and slowly spreading for as long as four years or more. “Being so far north of the quarantine zone and so close to a city, this area was outside the zone we intensively survey for sudden oak death each year,” said Navarro. “We are increasing our aerial and ground surveys in northern Curry County to make sure we find any other infestations that might be out there.”
Navarro said treatment will take several months to complete. The Legislature has allocated $1.7 million for detection and treatment of sudden oak death over the next two years with a further $190,000 coming in 2021 from the USDA Forest Service under a cooperative agreement, Navarro said. “Treating this area is estimated to cost about $1.7 million,” she noted.
Norma Kline with Oregon State University Forestry and Natural Resources Extension in Coos and Curry counties plans to provide information sessions about the disease to the public this summer in Port Orford. This will help local residents identify symptoms of sudden oak death so they can report any signs of it on their property.
A different strain of sudden oak death – the NA1 variant – has been killing tan oaks in Oregon since the disease was first discovered in Oregon in 2001. A European strain – the EU1 variant – was first found in Oregon in 2015. It turned up in wild tanoak trees this spring at a site in the Rogue River-Siskiyou National Forest, just across the Rogue River from the current sudden oak death quarantine boundary. Trees at that site have since been cut and piled ready for burning.
It is not known how the NA2 variant escaped into the wild. Although this is the first report of the NA2 variant being found on trees in nature, Oregon has been vigilant about monitoring and testing and is actively trying to slow the spread of sudden oak death, which 20 years after discovery is still confined to Curry County. By contrast, sudden oak death is now reported in forests in every coastal California county from the Oregon border to Monterey.
Read more about sudden oak death at https://www.oregon.gov/ODF/Documents/ForestBenefits/SOD.pdf.