Observation 184500: Heterobasidion occidentale Otrosina & Garbel.

Proposed Names

76% (2)
Recognized by sight: the orangey-peach young pore surface is, I think more characteristic of H. occidentale. But I am still not certain about the biogeography of this group and how it relates to identification

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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By: Christian (Christian Schwarz)
2014-10-27 14:40:14 -05 (-0500)

flesh (in at least some species) turns red in KOH.

But there are at least a handful of Fomitopsis in question, and F. pinicola isn’t in California, apparently:

Darv & Christian
By: Danny Newman (myxomop)
2014-10-27 14:35:10 -05 (-0500)

are there good field features other than host association, distribution and location on substrate that help delimit Heterobasidion spp.? I feel I have seen sturdy, sizeable conks on pines with less red belting than I’m comfortable with to merit calling them F. pinicola, and have often wondered if Heterobasidion is a better fit. Maybe context color and/or KOH reactivity?

By: Christian (Christian Schwarz)
2014-10-26 23:40:54 -05 (-0500)

Arrhenia epichysium in the second photo

H annosum not in the west
By: Darvin DeShazer (darv)
2014-10-26 22:45:39 -05 (-0500)

Heterobasidion irregulare the ‘P’ (Pine) type) can kill ponderosa pine, Jeffrey pine, sugar pine, Coulter pine, incense-cedar, western juniper, and pinyon pine; Fruits inside of stumps; popcorns on roots; All of North America

Heterobasidion occidentale the ‘S’ (Spruce/fir) type) can kill true firs, hemlock, Douglas-fir, and giant sequoia. Western North America.

Pine stumps can have either species, but H. occidentale is only found under the intact surface bark of pine stumps. A fruiting body on pine is H. irregulare.

Christian, I believe there was some discussion
By: Ron Pastorino (Ronpast)
2014-10-21 15:37:33 -05 (-0500)

by the NAMA identifiers about those two species, but I don’t recall the outcome.
I think both names may have appeared on the tag for these.

Created: 2014-10-21 15:00:07 -05 (-0500)
Last modified: 2014-10-26 22:41:31 -05 (-0500)
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