Sudden Oak Disease (SOD) is intensifying in Curry County, Oregon Department of Forestry surveys indicate, prompting state and federal agencies to step up measures to prevent the pathogen from spreading.
The NA1 variant of SOD has been in Curry County for years. Of concern, however, is a new strain: the EU1 hails from Europe and attacks Douglas firs, the economic driver of the state timber industry.
It is estimated that treating the areas identified in 2017, providing a 300-foot buffer and at $4,000 an acre, would cost $2.7 million.
“Given the large number of infestations, treatment priorities were set for 2017 based on genetic lineage, the potential for disease spread, the number of nearby sites and location within the quarantine area, in that order,” the report reads.
The NA1 variant, which primarily kills tanoak trees, got a toehold in the southwest corner of Oregon years ago and has slowly made inroads in Curry County. Last year, state and federal agencies chipped in more than $1.3 million to address SOD, with a priority on the new variant.
Despite the uptick in infested trees, the SOD quarantine area in Curry County has not changed since 2015 when it was extended to the California and Oregon border, the Oregon Department of Forestry (ODF) report reads. It extends from the border to the Rogue River, then east to the Skookumhouse Butte area, then doglegs down to the California border again.
The so-called “general infested area,” primarily surrounding Brookings, was, however, increased from 59 square miles to 89 square miles at the end of last year.
An estimated 30 percent of Curry County is in the quarantine area.
If the entire county is quarantined, it could have dramatic economic implications, said State Rep. David Brock Smith, R-Port Orford, who sits on the state task force addressing SOD. Items coming out of the area are already verified to ensure they don’t carry the SOD pathogen, but if the quarantine area comprises the whole county, other counties, states and even countries would likely not want to accept the products, which include timber, lilies and cranberries, among others.
Last year, almost 40 new SOD infestations were found beyond the general infested area and six within it. Eradicating the affected trees, assuming a 300-foot buffer area around the trees, would involve cutting on about 300 acres.
That doesn’t include the new EU1 virus found here in recent years — 199 trees were found last year and 43 more tests are pending — that would require treatment of 371 acres, the report indicates. There were five EU1 infestation areas — one of which was 2.5 miles away from any other known location.
Tests conducted by the state agency showed that seedlings planted under infected tanoaks were three to four times more likely to be infected under the EU1-infected trees than those under the NA1 trees. The EU1 pathogen also produces two to three more spores than the NA1 lab tests showed. And cankers on Douglas fir, tanoak and western hemlock were twice as big on EU1-inoculated trees.
The ODF has prioritized the EU1-infested trees in the quarantine area for treatment, which is underway. Because of that, however, trees with the other pathogen might not get treatment.
The Chetco Bar Fire burned through 27 infestation areas, as well. Ten of those sites had already been treated and four were undergoing work. A challenge there, however, will mean further investigation to determine if tanoak in the area died from the fire or SOD.
Stream-baiting, which involves sampling water for the pathogen and tracing its origin upstream to the source trees, continued last year and included 16 streams. Ten drainages tested positive, although many of those have also tested positive for the pathogen in the past.
Of note in the report was new stream-baiting of a tributary of Little South Fork Hunter Creek, which tested positive with the EU1 lineage.
Last year, the U.S. Forest Service provided the ODF with an additional $100,000 to eradicate the EU1 areas, the federal government is chipping in $23,000 and the state is increasing its contribution by $450,000.
Again, the EU1-infested areas will receive priority for treatment this year, the report reads.
This year, a helicopter survey was conducted Feb. 2 and on-the-ground checking of 25 dead tanoaks will begin soon. So far, two new infestations were found at or outside the generally infested area.