White Trunk Rot (Phellinus tremulae)
From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.
Importance- White trunk rot causes more wood volume loss in aspen than any other disease. Advanced decay and discoloration greatly reduce the value of trees as fiber sources. This rot is not a problem in plantations managed on short rotations.
|
Look For:
Standing trees:
- Hoof-shaped conks (fruit bodies). Conks are dark brown to black on the upper surface and light brown on the lower surface. The interior is dark brown with white flecks.
- Punky knots filled with dark brown material resembling the interior of conks.
- Trees with large branch stubs, broken tops, cankers, fire scars, and other old stem wounds.
Cut trees:
- Yellowish-white wood surrounded by a zone of dark, discolored wood (early stage of decay).
- Spongy, yellowish, wood surrounded by irregular black zones of discolored wood (advanced decay).
|
 Decay in cut logs.Photo by Linda Haugen, USDA Forest Service
|
|
Biology- Phellinus is a wound parasite that infects trees when spores (basidiospores) from conks land and germinate on suitable substrates. By the time large or multiple small conks become visible on infected trees, decay is usually extensive. Generally, less volume is lost in vigorous stands on good sites than in stands on poor sites.
|
 Fruit bodies (conks) of Phellinus.Photo by USDA Forest Service - North Central Research Station Archives
|
Monitoring- White trunk rot becomes more severe with stand age. In parts of the Lake States, aspen stands begin to deteriorate rapidly when they reach 50 to 60 years. Mature stands and stands damaged by fire, wind, ice, and other agents, should be considered for harvest before damage becomes too great. The volume of wood affected by hidden decay (early stage of decay or trees with no visible symptoms) can be equal to the volume of decay in trees with symptoms.
Control:
- No direct control is known, but loss can be minimized by harvesting aspen before decay becomes extensive.
- Harvest stands damaged by fire or weather early because such stands are susceptible to infection.
- Make regeneration cuts in overmature, defective aspen stands to bring these sites back to full production.
- Manage aspen to achieve uniform, well-stocked stands so natural pruning will minimize infection sites.
For Additional Information:
Ostry, Michael E. ; Walters, James W. 1983. How to identify and minimize white trunk rot of aspen. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station. 5 p.
|
