Brown cubical rot (sulfur fungus) Laetiporus sulphureus
Distribution: Throughout host range in B.C.
Host Susceptibility: Brown cubical rot affects many mature coniferous and deciduous hosts. The conifers affected
in B.C. include western hemlock, Engelmann, white and Sitka spruce, the true firs, larch,
spruce, ponderosa and western white pine, Douglas-fir and western redcedar.
Signs and Symptoms: The fruiting bodies are annual, fleshy to leathery, rounded edge shelf-like conks 2-3 cm
thick and up to 40 cm wide. They usually overlap in large clumps up to a square metre or
more in size. The upper surface of the conks is smooth to roughened and bright
orange-yellow in colour. The lower surface is sulphur yellow with fine, regular pores.
Older conks become dry, whitish-grey and crumbly, with a strong pungent sulphur
odour. Fruiting bodies rarely form on living coniferous hosts. Fresh conks are edible.
A light brown stain appears in the heartwood in the early stages of decay. As the rot
advances, the wood degrades into small, red-brown cubes. In the shrinkage cracks
surrounding the cubes, white mycelial mats may form.
Damage: Brown cubical rot in living trees is primarily confined to the butt log. The rot is well
established before fruiting bodies are produced. Therefore, the presence of conks indicate
extensive internal butt rot.
Can be confused with: Brown trunk rot (F. officinalis) causes similar tree decay in a number of conifers.
However, the fruiting bodies of brown cubical rot are bright yellow and shelf-like, often
forming large clusters, whereas brown trunk rot conks are hoof shaped or pendulous, and have
a distinctly bitter taste. Additionally, the brown trunk rot caused decay has thicker
mycelial mats and the rot usually extends further up the stem than the brown cubical rot.
Back to the Pest
Field Guide Index
Contact Tim Ebata
if you have comments on the presentation of this information.
BC Ministry of Forests
Forest Practices Branch
P.O. Box 9513 Stn. Prov. Gov.
Section phone: (250) 387-8739
Section fax: (250) 387-2136
Last updated February 19, 2002