Laminated root rot douglas-fir form
Base of tree
Damage, symptoms and biology
Western red cedar is rarely killed by P. weirii, damage being confined mostly to butt rot, which can extend 2 to 3 m up the bole of living trees; in cases of severe decay, up to 10 m. Most old-growth cedar has some degree of butt rot, much of which is caused by P. weirii weaken the tree and lead to stem breakage low on the bole.
Laminated root rot poses a major threat to its most important host, second-growth Douglas-fir. The disease causes root decay, which can cause significant growth reduction, and makes trees susceptible to blow down and stem breakage (the latter is rare in coastal trees).
Initial infection and spread of the fungus in a stand occurs when healthy roots come in contact with diseased roots. The fungus can remain viable in stumps and roots for many decades after tree death thus serving as a source of inoculum for subsequent rotations. Mycelia do not grow freely through the soil and spores are not believed to be important in disseminating the disease. Disease centres develop around infected stumps and expand radially at rates of about 30 cm per year.
Canadian Forest Service Publications
Information on host(s)
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