The scourge of the yellow trees: tackling swiss needle cast in the coast range

Abstract

Swiss needle cast (SNC), the yellowing disease of Douglas-fir evident in many parts of Pacific Northwest Coast Range forests, is caused by a fungus endemic to the region. The disease apparently caused no significant widespread injury until the 1970s, when Christmas tree growers began to report needle loss. Since the late 1980s, SNC has become increasingly severe in plantations of Douglas-fir in coastal Oregon and Washington, and more recently, in older naturally established stands.

In severely affected stands, symptoms of SNC include yellowing and premature loss of older foliage. In response to the outbreak, forestry organizations came together in 1996 to fund research that would (1) determine why this supposedly benign native disease became so virulent, (2) determine the impact the disease is having on forest stands, and (3) develop possible means to mitigate the impacts of the disease. The research is now coordinated through the Swiss Needle Cast Cooperative.

The Pacific Northwest Research Station has led the effort in examining the genetic variation in SNC tolerance/resistance and has assisted organizations in using these results in applied breeding programs. The Station also collaborates in research documenting the impact of the disease on tree growth and wood properties.

Citation

Duncan, Sally; Johnson, Randy. 2003. The scourge of the yellow trees: tackling swiss needle cast in the coast range. Science Findings 58. Portland, OR. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 5 p.