Battle against Sudden Oak Disease tough, but essential

By Stacy Savona, Sudden Oak Death program manager, Oregon Department of Forestry November 24, 2010 07:00 am

As you may have read in the Curry Coastal Pilot, the Oregon Board of Forestry recently met in Brookings and toured areas affected by Sudden Oak Death (SOD), the tree disease caused by the non-native pathogen Phytophthora ramorum. SOD is a relatively new disease to Oregon. Since its discovery in the Brookings area in 2001, forest managers in the public and private sectors have been working together to locate infected trees, eradicate the pathogen from infested sites, and slow the spread of the disease.

Cutting and burning infected and nearby trees may seem crude but it is the best disease management tool available to us. There is nothing we can spray to kill the pathogen or prevent trees from becoming infected. Cutting and burning infected trees, many of them still green, destroys the pathogen and reduces the potential for spread of air-borne spores. Unfortunately, it doesn’t always work as planned. Inconsistent funding often has delayed treatment and allowed the disease to spread before we can destroy it.

For the most part, the treatment is effective at eliminating disease from the site. When we sampled soil and vegetation on 230 infested sites that were cut and burned between 2001 and 2009, we found that the pathogen was present in vegetation on only 10 percent of sites, and in soil on approximately 40 percent of sites. We were unable to find that pathogen at all on more than 50 percent of treated sites. This level of success greatly reduced the rate of disease spread across the forest. Similar infested areas in northern California that have not been treated have expanded to an area 40 to 50 times as large as the Brookings infested area.

Our goal is to prevent spread beyond the current 162-square-mile quarantine area by continuing our program of early detection, eradication, host-removal in areas of probable disease spread, monitoring and research. We will continue this as long as we have funding and good cooperation, but we still face challenges. Brookings area weather is very conducive to disease spread, and delays in completing treatments allow the pathogen to spread during rainy periods. Funding is good now, thanks to an ARRA (American Recovery and Reinvestment Act) grant, but future funding is uncertain.

We haven’t completely eradicated Phytophthora  ramorum from our forests, but we’ve slowed it down and this has economic value. The size of the quarantine area hasn’t changed in three years. This alone has benefitted the nursery and forest industries that fear the economic impacts of an expanded quarantine area.

The potential ecological damage of the disease is troubling. If the tan oaks all die, what will be lost with them, and what will replace them? Where and when will the dead trees fall? Will we have increased sedimentation in streams? Will the deer and elk have enough food to sustain them with the loss of acorns? What other plant species might we lose that make southern Oregon unique? Large areas of dead trees would not only create an extreme fire hazard but would drastically change the character of the forest environment as we know it today.

We’re protecting more than the forests of southwest Oregon. Pest-risk models show that the pathogen could spread throughout western Oregon and elsewhere in the Pacific Northwest. Eastern U.S. hardwood forests are at high risk for sudden oak death, as are many parts of Europe.

We must continue this sometimes messy and inconvenient program to contain the disease, but we cannot be successful without the cooperation of the community. The willingness of landowners to help us locate dead trees and complete treatments on their property is critical, and it’s one reason we have had some success. Compliance with the quarantine rules and regulations is equally important. Continued funding is essential. We must continue this effort — we have too much to lose if we don’t.