Summary:
Heterobasidion annosum group is recognized by the thin, brown to blackish brown crust on the often grooved or irregular cap surface, and cream-colored pores and margin. The pores reacting strongly with Melzer''s reagent. When growing flat without a cap, the margin is often very distinct and slightly raised. Dextrinoid skeletal hyphae can be distinctive (see MICROSCOPIC). |Heterobasidion occidentale is primarily on true fir, hemlock, and Douglas-fir, pores are round to elliptic with about 6% elongated to somewhat daedaleoid, and pore density 8.6 +/- 0.07 pores per square millimeter, whereas Heterobasidion irregulare is primarily on pine and juniper, pores about 10% or more radially elongated to somewhat daedaloid, and pore density 7.3 +/- 0.12 pores per square millimeter (Ginns(28) for British Columbia). |The Heterobasidion annosum group in North America appears to belong to two intersterility groups: "the p-type, which occurs mainly on pine, incense cedar, hardwood and brush, and the s-type, which infects other conifer species. The p-type will infect both p-and s-type hosts, whereas the s-type is restricted to s-type hosts." (Allen(1)). |Heterobasidion annosum sensu lato according to Garbelotto and Otrosina consists of at least 5 species, of which two occur in North America: Heterobasidion irregulare Garbelotto & Otrosina Fungal Biology 114: 20. 2010 (corresponding to the p-type) and Heterobasidion occidentale Otrosina & Garbelotto Fungal Biology 114: 20. 2010 (corresponding to the s-type). They measured mean pore density for H. occidentalis in 2 California sites as 8.6 per square mm with 6% of pores irregular and for H. irregulare in California and Georgia sites as 7.3 per square mm with 11% of pores irregular (irregularity of pores is affected by orientation however). |Heterobasidion occidentale is thought to occur in BC and its range is given as western North America from AK to southern Mexico. (Otrosina(1)). Heterobasidion irregulare also occurs in the Pacific Northwest, at least in BC, whereas Heterobasidion annosum is limited to Europe, (Ginns(28)).

Chemical Reactions:
flesh does not turn red with KOH

Odor:
no particular odor (Lincoff(1)), strongly fungoid (Breitenbach)

Taste:
no particular taste (Lincoff(1))

Microscopic:
spores 4.5-6.5 x 3.5-8 microns [sic, but see other measurements below], nearly round to oval, minutely echinulate (spiny) or appearing smooth under light microscope, inamyloid, colorless, spores often difficult to find; basidia 4-spored, 16-22 x 5-6 microns, clavate, simple-septate at base; cystidia none; hyphal system dimitic: context generative hyphae 2.5-5 microns wide, colorless, "thin-walled, simple-septate, with occasional branching", context skeletal hyphae 3-5.5 microns wide, colorless, "thick-walled, nonseptate, dextrinoid, with occasional branching", trama hyphae similar, (Gilbertson), spores 3.5-5 x 3-4 microns (Lincoff(2)), spores 4.5-6 x 3.5-4.5 microns (Lincoff(1)), spores 4.5-6 x 4-4.5 microns (Breitenbach), "The dextrinoid staining of the skeletal hyphae in some basidiomata is hardly discernable and can take hours to develop", (Ginns(28))

Spore Deposit:
white (Lincoff(2))

Notes:
Heterobasidion annosum group has been found in BC, WA, OR, ID, ON, AK, AL, AR, AZ, CA, CO, CT, DE, FL, GA, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, NH, NJ, NM, NY, PA, TN, TX, VA, VT, WV, Jamaica, and Europe (Gilbertson(1)), and also Asia and Australia (Breitenbach).

EDIBILITY

no (too woody), (Lincoff(1))