New research has found that older Douglas-fir trees in Oregon are just as susceptible to Swiss needle cast as younger ones, suffering the same needle loss and in some cases almost stop growing. Photo from OSU.
Oregon’s state tree, the Douglas Fir, is under attack from a disease that’s spreading and intensifying through the Coast Range.
It’s called Swiss needle cast, a fungus that causes the tree to lose its needles and stunts its growth. Researchers with Oregon State University say the disease has gotten so bad, it’s damaging forests to the tune of $200 million per year.
They suspect global warming may be a cause.
Swiss needle cast is not new to Oregon’s forests and for a long time wasn’t considered much of a problem. But starting in the 1980s, researchers say the disease became much more widespread and got significantly worse in the late 1990s.
“It’s now clear that this epidemic is a new phenomenon, with far more severity and impact than anything we’ve observed from Swiss needle cast in the past,” says Dave Shaw, an assistant professor at OSU and director of Swiss Needle Cast Cooperative. “We’ve known of this disease for decades but it was considered a non-issue in terms of forest health. A perfect storm of conditions that favor this fungus has caused a major epidemic that is still growing.”
The “perfect storm” Shaw refers to includes how the forests are managed, plus a changing climate.
Oregon’s coastal forests used to be more diverse, with greater variety in the types of trees that grew there and greater variety in their ages. But as the forests were logged, the trees that came down were replaced mostly by Douglas Fir.
The disease also spreads more easily in warm temperatures and rainy spring seasons.
“We now know that weather is a driver in the epidemiology and spread of this disease,” says Bryan Black, an assistant professor of forestry based at OSU’s Hatfield Marine Science Center. “We can’t say yet whether climate change is part of what’s causing these problems, but warmer conditions, milder winters and earlier springs would be consistent with that.”
Young trees drop their needles, turn yellow and grow much more slowly when infected by the fungus Swiss needle cast. Photo from OSU.
In 2008, an estimated 376,000 acres of coastal forests were infected. But the researchers say it could spread to two million acres.
Most of the time, Swiss needle cast doesn’t kill the tree, but does slow its growth. In severe cases, the tree stops growing. “Tree growth has been reduced so much at severely-impacted sites that we could not actually find a growth ring that went all the way around some trees,” Black says. “At these sites the overall growth rate over the past 25 years was reduced by more than 85 percent in comparison to non-diseased trees.”
The researchers used to believe that the disease primarily only affected younger trees, those less than 40-years old. The hope was that the disease was something the trees would simply outgrow. But the newest research shows that older trees are just as vulnerable as younger ones.
Forestry officials have limited options to stop the disease. Fungicides work well, but are expensive and can damage the environment. One possibility is planting less Douglas Fir and using more western hemlock, red alder or other species.
Despite its name, Swiss Needle Cast is native to the Pacific Northwest. But, it was discovered in Europe in trees that had been imported from this region.
And, of course, the main concern is the loss of money value.
This disease might be perfect, actually. It’s like the trees are on strike against the capitalists who have logged them!