OREGON STATE UNIVERSITY

Disease found in twice as many fir trees as last year

09/23/1997

CORVALLIS - A 17-member research cooperative will meet at Oregon State University in October to discuss the spread and control of Swiss needle cast, a tree disease infecting thousands of acres of Douglas firs along Oregon's coast.

According to Greg Filip, an OSU Extension Service forestry specialist who is coordinator of the cooperative, aerial surveys conducted by the Oregon Department of Forestry found twice as many acres (about 260,000) infected by Swiss needle cast compared to a survey last year.

"This doesn't necessarily mean the disease has spread to twice as many trees in a year's time," said Filip. "Many of these trees were probably already infected. It just took another year for the effects to be visible from the air."

Still, the problem is severe, Filip says. "However, we don't yet know the exact economic damage," he said. "We are just now starting to put together data on loss of growth due to the disease. We should then be able to come up with a dollar per acre economic impact figure."

The disease makes young trees look like a "bottle brush," or as if they were going prematurely bald, says Katy Kavanagh, an OSU Extension forestry agent for Clatsop and Tillamook counties.

"The trees have no three-year-old needles, yellow two-year needles, but the new growth needles look just fine," said Kavanagh. "It was generally thought of as a disease that young trees grow out of, but it's now being seen in 75-year-old and older trees in the Oregon Coast Range."

Kavanagh, who is part of OSU's research team on the disease, said that Swiss needle cast once was thought to infect only young conifers such as those grown for Christmas trees. The disease originated in the northwestern United States and was taken back to Switzerland via infected trees.

Filip says the cooperative will discuss possible treatments.

"We know that fungicides work well on Christmas tree farms infected with Swiss needle cast," he said, "but this isn't an affordable option for forests. The fungicides would have to be applied by airplane after every rainfall. Thinning out diseased trees is another option as is selecting out trees that are genetically resistant to the disease."

The cooperative of representatives of the OSU College of Forestry, the Oregon Department of Forestry, the U.S. Bureau of Land Management, the U.S. Forest Service, the Coos County Forestry Department and 13 timber companies will meet at OSU's Peavy Arboretum Oct. 30-31.