OREGON STATE UNIVERSITY

Innovation in treating Swiss Needle Cast

The Swiss Needle Cast Cooperative was established in 1997 as a partnership between the Oregon State University College of Forestry and private, state and federal organizations to address challenges to the management of Douglas fir in Oregon and Washington caused by the Swiss needle cast epidemic.

The mission of the research cooperative is to conduct research to enhance productivity of Douglas fir and general forest health.

Swiss needle cast disease is caused by a fungal pathogen. Symptoms include yellow needles and premature needle abscission, resulting in sparse crowns as well as reduced diameter and height growth of the severely infected trees. Because no “silver bullet” cure for the disease has been found or currently appears within reach, research funding has gradually declined.

Doug Maguire, the Giustina Professor of Forest Management, says that continuing to research various aspects of the disease remains important for effective management in the presence of the disease. If managers know their Douglas fir stands are afflicted with Swiss needle cast, they can vary stand density and plant other species to minimize or offset the loss of production.

Back in the ’90s, the first step to learning about and managing the disease was to conduct a growth impact study. Senior Faculty Research Assistant Doug Mainwaring says a new plot network will expand on that research in a strategic way.

“It covers 100 or so stands along the entire length of the Coast Ranges,” he says. “We wanted to sample foliage from the trees to get a feel for their initial condition.”

The cooperative will continue to take measurements every five years in order to get a sense of what the growth losses are.

“It will also help us know if the disease is getting better or worse,” Mainwaring says.

The results of the study will have an impact on the decisions made by forest managers like Mark Gourley of Starker Forests. Unlike journal articles that incorporate only the findings from one small team of researchers, he’s glad the Swiss Needle Cast Cooperative brings a collaborative group of professionals and researchers to the table to discuss the problem the disease causes.

“I feel valued when we come to the table together with other foresters and researchers from various areas from inside and outside the OSU College of Forestry. It’s a unique approach, and it works,” Gourley says.

So far, the cooperative is finding that there is a climatic influence on the disease.

“If we have a wet spring and mild winter, that’s conducive to the fungus that causes Swiss needle cast,” Mainwaring says. “Depending on changes to our climate, people will take action one way or another. One of the smartest things to do is to plant other species in case the Doug fir fails, and I think that’s really important to continue.”

Results from aerial analyses in 2015 indicate a slight expansion, 0.6 percent, in the affected area relative to 2014, but it remains the most significant threat to Douglas fir plantations in western Oregon.

“Sustained growth losses over the previous 20 years have resulted in millions of dollars in lost timber and tax revenues,” said Gabriela Ritokova, Assistant Director of the Swiss Needle Cooperative. “In many cases, mid-rotation stands in the hardest hit areas have remained in an unproductive state, with managers hoping for a reprieve in disease levels.”