Swiss Needle Cast

John Cawston rewarewa at ihug.co.nz
Sun Sep 10 05:50:53 EST 2000


truffler1635 at my-deja.com wrote:

> From The Oregonian, Sept. 8, 2000, p D4
>
> RESEARCHERS SAY FUNGUS AFFLICTING DOUGLAS FIRS MAY HAVE PEAKED
>
> The epidemic hit along the northwest Oregon coast, causing many valuable
> trees to lose their needles
>
> By MATT SABO
> CORRESPONDENT, THE OREGONIAN
>
>         Aerial surveys the Oregon Department of Forestry conducted this
> summer indicate that he spread of Swiss needle cast, a fungus that stunts
> Douglas fir growth in coastal timberlands, may have peaked.
>         The fungus has afflicted trees on 283,000 acres of timberland in
> Oregon, down slightly from 1999's total of 295,000 acres, said Alan
> Kanaskie, a forest pathologist with the Forestry Department.
>         The agency says as much as 75 percent of state forest land in
> northwest Oregon is affected by Swiss needle cast. About 75,000 acres of
> trees with two years or less of foliage retention show severe damage from
> the fungus.
>         Scientists are uncertain whether the lower number in this year's
> survey is a result of mapping errors or whether the spread of the fungus
> is leveling off, Kanaskie said. "We'll see what next year's surveys
> hold."
>         Forest scientists said a cycle of cool, wet weather beginning in the
> 1990s triggered the rapid spread of the fungus. Swiss needle cast causes
> Douglas fir needles to turn yellow and fall off prematurely, slowing or
> halting tree growth. The fungus spreads by mobile spores.
>         Swiss needle cast thrives in wet weather, particularly in fog-laced
> slopes, and is concentrated within 20 miles of the coast from Lincoln
> County north into Washington state. Tillamook County forests have been
> hardest hit, Kanaskie said.
>         "The fungus was building, we think, for many decades," said Greg
> Filip, an associate professor at Oregon State University's College of
> Forestry. "It just took something to trigger it. We don't see an end,
> that's for sure. I think the end may come when we get some dry-weather
> climates.+i.+i.but that may not be for another 10 years."
>         Douglas fir has been Oregon's "bread and butter," Filip said. The
> tree grows quickly compared with other softwood species and is milled
> into studs and boards for housing.
>         Though the exact cause of the epidemic is unknown, OSU experts said
> intensive, even-aged cultivation of Douglas fir could be part of the
> problem, along with the recent climate trends. In the old-growth forests
> of the Northwest, which have trees of many species, sizes and ages, the
> fungus has caused no big outbreaks in recorded history, they said.
>         Private timberland owners are cutting diseased stands of trees and
> replanting them with a mix of species rather than growing plantation-
> style Douglas fir stands, Filip said.
>         Alternatives include hemlock, cedar, spruce and alder, but
> landowners' demand for seedlings exceeds supply, and nurseries are unable
> to meet orders, he said. "You may see some bar areas until they get some
> of the other species in there."
>         Barte Starker, executive vice president of Corvallis-based Starker
> Forests Inc., said he and other timber owners remain concerned about the
> spread of the fungus. "It caught us by surprise in that we've known about
> Swiss needle cast for years."
>         It first turned up in 1925, at a time when the United States was
> shipping young Douglas fir trees to Europe for planting. People in
> Switzerland discovered the fungus and warned foresters here, leading to
> the misnomer "Swiss needle cast."
>         The fungus showed up on Christmas tree farms in the Willamette
> Valley during the 1970s. That was potentially devastating because
> unhealthy or discolored yule trees are worthless. Christmas tree farmers
> fought the disease successfully with fungicides, but that would be
> impractical for timberland owners, who would have to spray the chemicals
> after every spring rain.
>         Swiss needle cast, native to the Northwest, most often turns into a
> full-blown disease in trees 10 to 30 years old. Some trees lose their
> needles after two years, others after a century or more.
>         Symptoms occur when microscopic spores, clinging beneath tree
> needles, germinate and plug breathing holes known as stomata. The fungal
> growth, which sprouts into tiny black blobs, seems to favor the warm, wet
> weather common to Oregon's coast.
>         Researchers are studying the fungus, searching for possible causes
> and potential solutions to the epidemic, and are trying to develop
> genetically resistant Douglas fir varieties.
>         The needle cast outbreak as reinforced the concept of planting
> diverse forests that are more resistant to cycles of disease or pest
> infestation, Starker said. Despite its toll, however, he sees a benefit
> to the epidemic. "Whenever we have a mini-crisis, we learn tremendous
> amounts and push ourselves to learn deeper about things."
>
> Comment by poster: While the article says most of the outbreak is located
> along the coast, there is a considerable amount present in the Cascade
> Range as well. The Cascade foothills of Clackamas county are well-
> involved, and have been for some time. Once again, it is time to assess
> the "traditional" re-planting regimen of only Douglas fir after logging.
> Plantation rotations are ripe for SNC. Interplantings of other tree
> species, including White pine, Whitepark pine, Western hemlock, Red alder
> and oak would strongly decrease SNC by spacing out potential host trees
> farther apart, and interrupting dispersal of spores. Several studies have
> also shown that Red alder mixed with Douglas fir tend to grow both trees
> more rapidly than a single-species planting of either species.

We've had this disease in New Zealand. We found that pure stands of D fir were
improved by regular, light thinnings. The species is reasonably shade tolerant
and has a high Mean Annual Increment from about age thirty (here). This had lead
us to keep the stands at high stockings, which seem to trigger the disease.

Keeping deep crowns seems to work for us.

JC






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