Annosus root disease
Publication date: December 10, 2024Heterobasidion occidentale
Trees with extensive decay in structural roots due to annosus root disease are subject to mortality and/or windthrow; this is often the only indicator that the disease is present in a stand.
One this page:
Description
Heterobasidion occidentale is a fungal pathogen that causes annosus root disease in British Columbia with a related species Heterobasidion irregulare recently detected in BC. Annosus root disease mostly causes butt rot on spruce, true firs, and western hemlock.
Annosus root disease is found in coastal and south eastern regions of British Columbia. View the distribution map (PDF,530KB)
Host tree species
While western hemlock is the principal host but other true firs, Douglas-fir, white and Sitka spruce, western redcedar, and lodgepole pine are also attacked. All ages of tree are susceptible.
Damage symptoms
Trees may display few outward signs of infection but decay may extend 15 meters up the trunk. Younger trees may show reduced leader and branch growth, yellow foliage and a distressed cone crop. Older trees may experience butt rot leading to mortality or windthrow.
Management
There are several interventions to address annosus root disease 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 annosus root disease. Read a detailed guide on root disease management.
Further reading
Read the unabridged technical text and see more images in the Field Guide to Forest Damage in B.C. (PDF, 6.5MB)