Oregon: Sudden oak death quarantine expanded

Sudden oak death quarantine expanded for Oregon coast

Oregon has done a good job of keeping the tree-killing disease sudden oak death from exploding in the wild as it has in California. But any chance of eradicating the disease from the Southern Oregon coast, where it was first found in 2001, will require an expansion of the Curry County quarantine previously in place. Following public hearings held late last year, the Oregon Department of Agriculture is increasing the sudden oak death quarantine from some 26 square miles to about 162 square miles based on additional detections of Phytophthora ramorum, the fungus that causes the disease. The site, northeast of Brookings, remains the only place in Oregon where P. ramorum has been found in the natural environment.

"Our eradication efforts have worked very well at keeping sudden oak death from spreading to the rest of the state, but they haven't eliminated the disease," says Dan Hilburn, administrator of ODA's Plant Division. "P. ramorum has spread a little bit each year since we first discovered the disease nearly seven years ago, and we are continuing the eradication."

The fungus-caused disease has left a trail of dead trees in central and northern California ever since it was first detected in the San Francisco Bay Area in the mid-1990s. P. ramorum invades susceptible trees through the bark, killing the entire tree or portions of the tree.

Certain species of oak commonly found in southwest Oregon, including tanoak and black oak, are very susceptible. But P. ramorum also infects rhododendron, huckleberry, madrone, myrtle, and several other shrubs.

P. ramorum was detected in Curry County about the same time it was first found in Humboldt County in northern California, where efforts to mobilize an eradication effort that includes cutting and burning of diseased trees did not materialize. Today, about 6,000 acres in Humboldt County have been affected by the disease compared to about 180 acres in Curry County.

"We haven't been able to get rid of it in Oregon, but it hasn't gotten away from us either," says Hilburn. "There is still a possibility that we can eradicate the disease. No one else in the world has ever eradicated a fungal disease like this from the wild. So the fact that we are still in the game is a remarkable achievement."

In order to be successful, Oregon officials have had to increase the quarantine area. Five new sites of P. ramorum have been detected outside the original 2007 quarantine area. While it is clear these are not new introductions but part of the original infestation in Curry County, some of the new sites are more than two miles from past sites.

That means the disease is jumping around a bit. Not every susceptible plant and tree within the quarantine area has the disease, but they may have been exposed.

"In order to keep the quarantine boundary so it contains all the possibly infected sites including those we don't yet know about and won't be able to find until next year's survey we've expanded the quarantine to a three mile buffer from all known infested sites," says Hilburn.

The quarantine is designed to keep sudden oak death from being spread through human activity by keeping potentially infected plant material from being transported from the area.

Signs are posted at all entrances informing people of the quarantine. Inspection and certain requirements are, for now, part of the way of life within the area. For many residents, there shouldn't be any change as long as at-risk plant material is not transported outside the quarantine area. For others, there will be an impact.

"There are nurseries and a timber mill within the expanded quarantine area that must now meet specific requirements set by USDA-APHIS (U.S. Department of Agriculture's Animal Plant Health Inspection Service) in order to move products outside the area," says Nancy Osterbauer, ODA Plant Health Program Manager.

Meanwhile, survey and eradication efforts will continue for a seventh straight year. Interagency cooperation has been a key to the project. The U.S. Forest Service (USFS) and Oregon Department of Forestry (ODF) have been responsible for aerial observation and detection of dead or diseased trees. ODF and ODA have been active in monitoring the spread of the disease on the ground. ODF has had the lead in cutting and burning the infected plant material while ODA monitors success of the treatment.

Oregon State University has provided the laboratory confirmation of P. ramorum when survey samples are taken. No single agency can provide the necessary resources to undertake the eradication project, but combined, success is possible. Research shows the disease can spread through wind-driven rain. That's why it is important to cut down affected trees quickly to take them out of the canopy and keep the fungus from splashing onto other trees and shrubs.

The disease can also be found in the soil and in water. USFS and ODF have been baiting more than 70 streams in southwest Oregon with rhododendron leaves as an early detection method for the disease.

The intensive monitoring and survey work underscores the importance of keeping the disease in check and confined to the original Curry County site.

Not only is the state's forest ecosystem and timber industry at risk, an important nursery industry is doing all it can to keep the disease from establishing in some of the susceptible plants grown and shipped from Oregon.

"There is always the possibility that the disease will spread naturally up the coast and inland and despite our best efforts there is no magic bullet," says Osterbauer.

"But without everyone's efforts the past few years and our current plans to keep it from artificially spreading, there would be a much larger area of concern."

Oregon officials hope the expanded quarantine will help at least buy some time for scientists to come up with a new and better plan to deal with P. ramorum and sudden oak death.

Source: Curry County reporter

For more information, contact Dan Hilburn at (503) 986-4663.