WWETAC Projects

Project Title: Adapting and improving Swiss needle cast management tools to incorporate climate change projections

Principal Investigators: Jeffrey K. Stone, Leonard B. Coop, Dept of Botany and Plant Pathology, Oregon State University, Corvallis, OR.

Collaborators: Greg Filip, USDA Forest Service, Portland, OR; Alan Kanaskie, Oregon Dept. of Forestry, Salem, OR; Dan Omdahl, Washington Dept of Natural Resources, Olympia, WA; David Shaw, Dept. of Forest Resources, Engineering and Management, Oregon State University; Ian Hood, Scion (NZ Forest Research Institute Ltd), Rotorua, NZ; and Michael Watt, Scion (NZ Forest Research Institute Ltd), Christchurch, NZ

Key Issues/Problem Addressed:

Swiss needle cast (SNC) disease (caused by Phaeocryptopus gaeumanni, an ascomycete fungus that is native throughout the range of its host Douglas-fir, Pseudotsuga menziesii, is steadily increasing in severity over the past two decades in western Oregon and Washington due to climatic variables. Severe defoliation and growth losses of 20 to 50 percent because of Swiss needle cast have been reported for about 150 000 ha of Douglas-fir plantations in western Oregon since 1996.  An improved risk assessment model is needed in order to accurately forecast region-wide SNC disease impacts related to anticipated climate change.

Setting and Approach:

Spatial climate based models for predicting the distribution and severity of Swiss needle cast disease were developed using multiple data sets. Regional predictions for SNC impacts were predicted for 2040 and 2090 by applying climate-based disease models for current distribution using downscaled global climate models (GCMs).

Key Findings:

  • Climate factors most highly correlated with pathogen abundance are winter temperature and spring leaf wetness, and a model for prediction of disease severity based on these factors accounts for 77 percent and 78 percent of the variation in 1- and 2-year-old needles, respectively, for western Oregon sites.
  • A trend of temperatures increasing by 0.2 to 0.4 °C during the winter months and spring precipitation increasing by 1.6 to 2.6 cm per decade since 1966 suggests that regional climate trends are influencing the current distribution and severity of Swiss needle cast disease.
  • Forecasts of climate change in the Pacific Northwest region predict continued increases in temperatures during winter months of about 0.4 °C per decade through 2050, suggesting that the severity and distribution of Swiss needle cast is likely to increase in the coming decades as a result of climate change, with significant consequences for Pacific Northwest forests.
  • Under the most extreme emission combination, the current ‘epidemic area’ (west of -124.10 and north of Gold Beach in western Oregon) was predicted to increase from the current 3700 km² in to about 5700 km²  by 2040, and to double by 2090.
  • All global climate modeling scenarios through 2090 predicted that SNC impacts would remain in the Coast Range; disease predicted for the Cascade Range remains relatively insignificant.


A climate-based disease prediction model is being developed as an online, interactive tool that can be used to guide further research, conduct extended model validations, perform climate change scenario analyses, and eventually to provide short- and long-term disease risk predictions and management cost/benefit analyses. The model will be useful for prediction of disease development trends under different climate change scenarios and temporal scales.


Stone, J.K, Coop, LB, and Manter, DK. 2010. A spatial model for predicting effects of climate change on Swiss needle cast disease severity in PNW forests, Pages 145-156 in J.M. Pye, M.H. Rauscher, Y. Sands, D.C. Lee, J.S. Beatty, technical editors, Advances in threat assessment and their application to forest and rangeland management, USDA,Forest Service Gen. Tech. Rep. PNW-GTR-802. Portland, OR. (PDF, 656 KB)