Management of Sunnyside’s Root Rot Disease
Laminated root rot is a tree disease caused by the fungus Phellinus weirii (or P. sulphurascens). The fungus is widespread throughout BC and is naturally occurring in many ecosystems in the Pacific Northwest. Locally, the disease can cause the death or decline of evergreen species including Douglas-fir, grand fir, Sitka spruce and Western hemlock. In Sunnyside Acres Urban Forest, laminated root rot was identified as a forest health concern in 1999. After extensive research and public consultation root rot management activities started in 2003.
The earlier removal of red alder trees made post-fire Douglas-fir seedlings far more susceptible to the root rot fungus. Over the years, as the Forest grew back from fire, many of the alder trees were cut for firewood, a practice that is now, decades later, having a negative impact on the Forest. Many Douglas-fir trees are succumbing to the laminated root-rot fungal disease. If the alder had been retained, it would have inhibited the fungus and, during its 70-100 years of life, acted as a “sanitizing” agent. As Douglas-fir root systems decayed, the host for the fungus would have been depleted during the alder era.
Laminated root rot fungus spreads by root to root contact at the rate of 50 cm per year and threatens the health of the Douglas-fir forest. In an effort to prevent the spread of the root-rot the decision was made, reluctantly, in 2003 to fell trees to create a ten metre wide containment or quarantine belt, and to replant with 2325 deciduous species around the centres of infection. The goal was to ensure the roots of the remaining diseased trees would not contact the roots of other non-infected, healthy trees. Measures have also been taken to address the risk to public safety and wildfire hazard, conditions created by the root-rot disease.
Continued management relies on close monitoring of the spread of root rot within the Forest.
The photo above is an example of root root. Note the amount of fungus and decayed material present.