By Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension, Benton, Linn & Polk Counties
The short answer, unfortunately is ”yes”, but the news was clearly mixed when researches and land managers gathered for the Annual Meeting of the Swiss Needle Cast Coop (SNCC) in Corvallis on December 4. They met to review progress in learning more about this native disease, how it affects trees and forests, and how to manage forests in the affected areas.
The meeting included updates on this year’s aerial survey, progress in establishing the next generation of research plots across western Oregon, the effects of thinning and other management activities on foliage retention and growth, and improvements in remote sensing and growth modeling abilities. Some of the things I picked up this year included:
- The disease is intensifying but not expanding greatly. That is to say, we are certainly seeing more severe disease symptoms in places, but mostly within areas where it has been a problem before, and the footprint of highly affected area does not seem to be growing very dramatically. The disease was detected on over 586,000 acres in 2014, which is up significantly from 18 years earlier (131,000 acres in 1996). The main area of impact remains near the coast, generally within 25 miles, except for an active area around Mary’s Peak.
- Thinning pre-commercially does seem to help improve needle retention, but only in the healthiest trees and in the lower part of the live crown.
- Unlike other stressors, such as drought, it seems that SNC-weakened trees are not highly attractive to Douglas-fir beetles.
- A new tree ring analysis suggests that Swiss Needle Cast (SNC) seems to be periodic, and that outbreaks have occurred at roughly 30 year intervals since the mid 12th century, the time of the Renaissance.
- The same study detected indications of SNC outbreaks in each of the plots studied from the Coast to the high Cascades. Although a small study, this suggests that SNC is everywhere that Douglas-fir is.
- An ODF economic analysis of the impacts of SNC in Oregon looked at 10 – 70 year old forests of the Oregon Coast Range. Based on an average 20% growth reduction of Douglas-fir where the disease has be detected in the aerial surveys, they concluded that volume loses to SNC in this age class exceeds 190 million board-feet per year, with an estimated log value of $78 million/year. The economic impact to Oregon’s economy is equivalent to 2,100 jobs, representing $117 million in labor income and $10 million in income tax, and including a loss of $700,000 in harvest tax. Ouch.
So this disease continues to cause damage (albeit sub-lethal damage) across a large area of coastal Oregon where it is most severe and noticeable, but it can be found in the valley and throughout the Douglas-fir growing region. This is really not new, but researchers are concerned about new reports of disease development in the foothills of the Cascades. We saw some heavily affected stands there, outside Sweet Home earlier this year. The Cooperative Aerial Survey conducted by USFS and ODF will include the western Cascades between the Columbia River and Eugene in 2015. Find out more about the work of the Swiss Needle Cast Coop including aerial surveys and past reports at the SNCC website, and watch for a tour this spring, when symptoms are at their ugly peak, to be organized by the Linn Chapter of SWA and OSU Extension.
Check out the November issue of Science Findings from the PNW Research Station for more information on Swiss needle cast: Fingerprints of a forest fungus: Swiss needle cast, carbon isotopes, carbohydrates, and growth in Douglas-fir