9/2/2014

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Study warns Douglas fir root rot could get worse

Study warns Douglas fir root rot could get worse
Old growth Douglas fir trees stand along the Salmon river Trail on the Mt. Hood National Forest outside Zigzag, Ore., in this June 25, 2004 file photo. (AP Photo/Rick Bowmer)
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SPOKANE, Wash. (AP) — A new study has warned that a fungus that devours the roots of Douglas fir trees in the Northwest could become a bigger killer as the climate changes.

Laminated root rot occurs from Montana to the Pacific Ocean and already costs the timber industry millions of dollars each year.

The Spokesman-Review reported Tuesday that if the disease doesn't kill the fir trees outright, it leaves them weakened and susceptible to bark beetle attacks and uprooting during wind storms.

The study was overseen by the Washington Department of Natural Resources.

"Tree stress plays a big role in how vulnerable these stands are to root fungus," said Karen Ripley, the agency's forest health program manager.

Climate change forecasts for warmer temperatures and more frequent droughts mean the firs will be more susceptible to the fungus, she said.

Foresters have known about laminated root rot since the 1940s, but much about the disease remains a mystery. Ripley was part of a study panel that recommended a deeper look at the molecular biology and genetics of the fungi-caused root rot and its interaction with host trees. Other panel members included scientists from the University of Washington, Weyerhaeuser Corp., the U.S. Forest Service, Canada and the Pacific Forestry Center.

Due to retirements, Washington universities don't currently have researchers studying forest pathology, Ripley said. That's an issue that panel members want to bring to the Washington Legislature's attention, she said.

Douglas firs are a keystone species, valuable both economically and ecologically. Laminated root rot occurs across the species' range, from Montana to the Pacific coast, and from British Columbia to Northern California.

Root rot lowers the Washington Department of Natural Resources' timber harvest yields in Western Washington by 5 to 15 percent annually. Over a two-year period, that reduced revenues to the state's public school and university trust fund by $10 million, according to agency estimates.

The disease also hurts recreation and biodiversity, Ripley said. For instance, big, old trees had to be removed from a Lake Wenatchee campground because they were infected with root rot and had become hazards, she said.

In addition, root rot is closely affiliated with bark beetle outbreaks. Beetles can sense which trees are in poor health and choose them for host trees, Ripley said.

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Information from: The Spokesman-Review

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