Laminated root rot
Last updated on January 30, 2025Coniferiporia sulphurascens
(previously known as Phellinus weirii)
Laminated root rot is a native root disease that occurs throughout the range of Douglas-fir in British Columbia.
It is an important disturbance agent that provides valuable wildlife habitat and contributes to tree species diversity but can cause considerable losses in Douglas-fir stands being managed for timber.
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Description
Laminated root rot is the most damaging tree disease of coastal Douglas-fir and causes significant losses in managed Douglas-fir stands in the southern interior. It spreads almost exclusively by root to root contacts and forms discrete root disease centers which can be easily mapped prior to harvest. Large centers that are visible from the air are common in some parts of the southern interior. Laminated root rot can remain viable and able to reinfect trees in large stumps and roots for up to 100 years. In old growth Douglas-fir stands, visible root disease centers are less common and the disease can be difficult to detect.
Laminated root rot is found throughout the range of Douglas-fir in the province, especially in coastal Douglas-fir (CDF) and western hemlock (CWH), interior Douglas-fir (IDF) and Interior Cedar hemlock (ICH) biogeoclimatic zones. Near its northern limit in central BC, it is most commonly found on south and southwest aspects (particularly along the north side of large lakes. In the dry southern interior, it is most commonly found on east and north facing slopes at low to mid elevation.
View the distribution map.
Host tree species
Douglas-fir and grand fir of all ages are the most susceptible, with other conifers varying in susceptibility. Western redcedar is rarely infected.
Damage symptoms
Laminated root rot forms root disease centers that can vary in size from one or two trees to many hectares in size. Individual infected trees show reduced leader growth, thin yellow foliage, and distress cones.
The disease causes extensive root rot which results in blowdown with root balls with little or no root plates. It is named after the advanced decay which often separates the annuals rings into layers. Larger than normal brown whiskery looking hyphae that are associated with zone line formation are a characteristic of this fungus. The fungus occasionally produces resupinate annual fruiting bodies but they are not useful for field location.
Read a detailed list of symptoms (PDF, 205KB)
Management
There are several interventions to address laminated root rot to minimize future losses. Regenerating with less susceptible species that are ecologically appropriate and the removal of stumps post-harvest when appropriate are the recommended treatments for laminated root rot. Read a detailed guide on root disease management. https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/forestry/forest-health/forest-health-docs/root-disease-docs/rootdiseaseguidebookjune2018_4.pdf
Identification images
Further reading
Read the unabridged field guide text and view images of laminated root rot in the Field Guide to Forest Damage in B.C. (PDF, 6.5MB)