Sudden Oak Death Is Still Spreading, Still A Threat

Jun 17, 2015

Reports on Sudden Oak Death don’t seem to be nearly as common as they were a few years ago. The invasive plant disease, which has devastated oak stands along the West Coast, continues to spread in northwestern California and southwestern Oregon. But funding, public engagement, and solutions have been hard to come by.

A tan oak tree in Humboldt County, killed by Sudden Oak Death. Oaks have no natural resistance to the disease, and suffer 100 percent mortality when infected.
Credit Courtesy UC Agriculture & Natural Resources

Remember Sudden Oak Death? That’s OK, a lot of people have forgotten about it.  

Yana Valachovic: “For me the challenge is communicating to the public the disease has not gone away; in fact, it’s actually getting substantially worse.”

Yana Valachovic is director and forest advisor for the UC Cooperative Extension office in Humboldt and Del Norte counties. She has worked with Sudden Oak Death since it first came to the area in 2002.

Yana Valachovic: “Less than 2-percent of Humboldt County’s potential at-risk habitat has been infested. In 2.25 million acres we’re talking about 30,000 acres of land. So lots and lots of land has yet to be impacted by this disease. And if you look at an average rate of growth and expansion per year it’s been about 3,500 acres on average each year.”

Sudden Oak Death is caused by a non-native plant pathogen called Phytophthora ramorum. Since first being discovered in Marin County twenty years ago it has spread to 15 counties in Northwestern California. 

In Oregon, only Curry county in the extreme Southwest corner of the state,  has been infected. The disease has never jumped over the coastal range. It has also never been successfully treated. Dr. Everett Hansen is a retired forest pathologist from Oregon State University.

Everett Hansen: “Now we are 10 to 15 years down the line. It’s pretty clear we are not going to eliminate it. Do we do anything?

Like California, Oregon has shifted its management approach from one of eradication to one of containment.

Everett Hansen: “The cost-benefit analyses that have been done - and they’ve been done several times - show that it is cost-effective to do what we’re doing. To slow the spread of the pathogen, even if we can’t eradicate it.”

This is the approach that has been taken in Redwood National Park which first became infected just last summer. Leonel Arguello, chief  botanist for the park, says Phytophthora has over 100 plant hosts - such as the bay laurel tree - that it does not kill. But it’s the oak species that are a primary concern.

Leonel Arguello: “This disease challenges us to find a way to protect tan oaks, which are absolutely killed 100-percent. There seems to be no natural resistance found yet. And our preferred technique at this point is once we’ve identified the infection area and created a buffer around there we will kill all tan oak and bay trees that are in the canopy, both within the infection site and within a 100-meter area around the infection site.”

Just south of Redwood National Park Sudden Oak death is now confirmed  to be just  five miles from Hoopa Indian land.

Nolan Colegrove: “A lot of tribal folks from this part of the country, one way that they describe themselves is ‘K’iwinya'n-ya:n' . And what that refers to is ‘Acorn Eaters’.

Nolan Colegrove of the Hoopa tribe says Sudden Oak Death is a major concern in a culture that has long revered oaks and their acorns.

Nolan Colegrove: “It is a critical part of the food supply for native people in this area. It plays an integral role in all of our ceremonies. And the ecological system out there really starts with the acorn being sort of the center. It is something that if it is threatened is going to threaten a way of life.”

Many who work with Sudden Oak Death admit the approach has shifted from one of crisis and urgency to one of containment and survival. Yana Valachovic of UC Extension feels this shift goes a long way toward  explaining the drop-off in media coverage and public engagement.

She also says there are two challenges that leave scientists in a more reactive than proactive mode.

Yana Valachovic: “The wild lands of California don’t have a single agency that’s responsible for controlling invasive introductions. Secondarily, there is no funding source that is set aside to manage these kind of epidemics. And so everything is piecemealed together: piecemealed responsibility, piece-  mealed in funding to address these issues.”

And funding may be the biggest issue of all. Five years ago the Forest Service provided one and a half million dollars nationwide for Sudden Oak Death research. Last year that amount was zero. Now any funds which are granted by the Forest Service can only go towards monitoring, containment, and education.

Which raises the question:  how will we learn more about this disease that is spreading through our forests at a clip of about 5 miles per year?