AP News, July 25th, 2007
Coastal state forests are experiencing a resurgence in Swiss needle cast disease, a fungus that kills the evergreen needles on Douglas fir trees by interrupting the process of photosynthesis.
Aerial surveys conducted by the Oregon Department of Forestry show 338,543 acres infected by the disease _ almost double the 2004 total, The Daily Astorian newspaper reported.
The fungus thrives in warm, wet conditions on the coast. The disease turns needles yellow before the tree "casts" them off. The fungus doesn't kill the trees, but it reduces their growth rate by 20 percent to 50 percent.
Surveys from 2003 to 2005 showed a coastwide decline in the severity of infection, prompting forest pathologists to credit efforts to diversify Douglas fir tree stands with other species such as hemlock and cedar. Foresters also selected hardier Douglas fir trees in hopes of finding genetic strains that were more tolerant of the fungus.
"The fact that we're up almost as high as we were in 2000 is fairly concerning to me because in the last seven or eight years people have been doing a lot to manage the disease," said Alan Kanaskie, a Department of Forestry pathologist.
Kanaskie said there's not a whole lot more foresters can do to contain the disease. A fungicide would solve the problem, he said, but it would be expensive and risky to spray it over the hundreds of thousands of acres of infected coastal forestland.
The disease tends not to spread inland more than about 18 miles because of weather conditions, Kanaskie said, so forests in the Willamette Valley are protected.
The surveys show that Tillamook County has the most extensive damage. About 70 percent of the stands in the Tillamook State Forest are Douglas fir, and about 40 percent of the entire forest is affected by Swiss needle cast.
Assistant Tillamook District Forester Wayne Auble called his forest the Swiss needle cast "epicenter." After the Tillamook burn, the forest was replanted with Douglas fir, Auble said, creating a "monoculture" that is more vulnerable to the disease than forests with a variety of tree species.
"We're going under the assumption that the disease is going to be a continued presence, so we have to figure out how to manage with it," he said. "We've tried lots of things. There's no magic bullet."
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Information from: The Daily Astorian, http://www.dailyastorian.com
