[6] Identification in affected wood, known as white pocket rot, includes symptoms in the form of dark discolouration around the heartwood near the base.

[citation needed] Distinction from H. irregulare is difficult as both share similar morphologies, distribution, and host range.

It is also of high importance to the Abies religiosa forests in Central Mexico that are the winter home for the monarch butterfly (Danaus plexipus).

[8] Other notable hosts include sitka spruce (Picea sitchensis) as well as numerous deciduous trees such as red alder (Alnus rubra), bigleaf maple (Acer macrophyllum) and pacific madrone (Arbutus menziesii).

This contrasts the Eurasian S-type species, H. parviporum, which has a fairly strict host range of spruce, fir, and larch.

Spores are present year-round, due to the perennial fruiting bodies, with the greatest quantity detected during spring and autumn in the Pacific Northwest.

Infection weakens the roots and will travel up to 15 meters (49 ft) up the heartwood affecting wood quality and yield.

[citation needed] Control measures for H. occidentale focus on limiting the exposure of stumps for colonization by basidiospores.

Basidiospores of H. occidentale can quickly colonize exposed stumps after logging, or pre-commercial thinning disturbances but infection rates are low due to competition with other saprotrophic fungi.

Covering exposed stumps with a chemical barrier such as borax or urea is used in other parts of North America to control H. irregulare.