7/13/2023 0 Comments Needle blight in fir![]() ![]() The findings erase any hope that older trees will "outgrow" the susceptibility to this disease, the scientists concluded. This study, based on examinations of rings in naturally-regenerated trees more than 80 years old, for the first time showed that they are very susceptible as well. It used to be thought that the disease primarily affected only younger trees, mostly less than 40 years old and predominately the 10-30 year age group, the researchers say. Reductions in growth of 20-30 percent are fairly common, and sometimes higher. Even-aged stands of vulnerable Douglas-fir allow the fungus to build up to much higher levels, releasing spores that can literally spread with the wind. Since Douglas-fir was a small component of these forests, it appears the disease was relatively insignificant. "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."Īnother key suspect, scientists say, is the planting for decades of a monoculture of Douglas-fir in replacement of coastal forests, which previously had trees of varying ages and different species. "We now know that weather is a driver in the epidemiology and spread of this disease," said Bryan Black, an assistant professor of forestry based at OSU's Hatfield Marine Science Center. The warm, wet conditions within 20 miles or so of the Pacific Ocean make those areas a hotspot of disease in coastal Oregon and Washington. ![]() Wet, drizzly conditions in May through July are also important. The new study concluded that warmer conditions, especially from March through August, are associated with significantly reduced growth in diseased trees, which may reflect earlier fruiting of the fungus. Prior to this four-year period, it had affected as much as 300,000 acres only once in the 14-year history of aerial detection surveys, researchers say.ĭepending on the multiple factors that influence it, it's possible it could ultimately have an impact on up to two million acres of forests near the Oregon coast, and change the face of forestry in a huge region. The disease has now been identified at varying levels of severity in western Oregon on more than 300,000 acres in each of the past four years, peaking at 376,000 acres in 2008. A perfect storm of conditions that favor this fungus has caused a major epidemic that is still growing." "We've known of this disease for decades but it was considered a non-issue in terms of forest health. "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," said Dave Shaw, an assistant professor at OSU and director of a cooperative designed to fight this disease. Starting in 1984, an epidemic began to develop, and it significantly worsened after 1996. ![]() However, it caused significant problems only in recent decades along the coast. It rarely kills trees but causes discoloration, loss of needles and growth reduction, and is common in the Pacific Northwest wherever Douglas-fir grows. Swiss needle cast is a native fungal disease specific to Douglas-fir that was first described in Europe. The newest findings were just published in Forest Ecology and Management, a professional journal. Scientists in the College of Forestry at Oregon State University have also found that this disease, which is affecting hundreds of thousands of acres in Oregon and Washington and costing tens of millions of dollars a year in lost growth, can affect older trees as well as young stands - in some cases causing their growth to almost grind to a halt. ![]()
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