OSU News Service

Forestry researchers at Oregon State University have developed a computerized risk analysis system to help predict the vulnerability of specific sites to Swiss needle cast, a serious problem in Coast Range forests that cuts tree growth and causes losses of more than $200 million a year.

The model should be available to landowners by early next year, and may help address a resurgence of the problem. Since 2004, the number of trees with Swiss needle cast has doubled to 340,000 acres.

“This new risk-rating model should be a reliable predictive tool so that landowners can make more informed decisions on what tree species to plant,” said David Shaw, an assistant professor in the forest science department.

Swiss needle cast, a fungal disease of Douglas fir that is native to the Pacific Northwest, is mostly an issue in areas within 20 miles of the ocean, where warm, wet conditions favor its growth.

It’s a cyclical problem that is made more severe by warmer winters, wetter springs and extended drizzle.

Historically, the fungus was a minor concern in this region, which was dominated by hemlock and Sitka spruce trees, with only smaller amounts of Douglas fir. But with intensive forest management during the past century, the varied tree species were often harvested and replaced with a monoculture of Douglas fir, which grew well and commanded higher market prices.

A series of workshops will be conducted next year to help private and industrial landowners learn more about the new risk-rating model and other steps to address this problem, Shaw said.