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Remarks (public):For a complete description including images see 
Remarks (internal):Baxter (1943) states that this is one of the few species of fungi which cause heart rot in living trees which can also cause decay in structural timbers, at least in hardwood timbers.
Description type:Non-original description 
Description:Laetiporus sulphureus (Bull.: Fr.) Bondartsev & Singer, Ann. Mycol. 39: 51, 1941.
= Polyporus sulphureus Bull.: Fr., Syst. Myc. 1: 357, 1921.
= Polypilus sulphureus (Bull.: Fr.) P. Karst., 1879.
= Leptoporus sulphureus (Bull.: Fr.) Quel., 1888.
= Cladomeris sulphurea (Bull.: Fr.) Bigeard & Guillemin, 1909.
= Tyromyces sulphureus (Bull.: Fr.) Donk, 1934.
= Grifola sulphurea (Bull.: Fr.) Pilat, 1934.
Carpophore (basidiocarp) annual, lignicolous, sessile or attenuate at the base, appearing substipitate, compound in rosette-like or imbricate clusters. Pileus 7-20 x 4-16 x 0,5-3 cm, dimidiate to flabelliform, connate, fleshy when fresh, drying torigid and brittle. Upper surface pubescent to nearly glabrous, salmon-coloured to sulphur-yellow or bright orange-yellow or fleshy-white, drying to almost white, margin obtuse thick, rounded, undulate to lobate, concolorous, sterile below. Pore surface bright sulphur-yellow, fading with age, poroid; pores angular to somewhat irregular, 2-4 per mm, dissepiments even to somewhat dentate, thin; tubes concolorous, in one layer 1-4 mm deep; context white, bright yellow or salmon, firm cheesy when fresh, friable on drying, 0,3-2,7 cm thick, azonate. Basidia narrowly clavate, 15-18 x 5-7 µm, with four sterigmata. Basidiospores ellipsoidal to ovoid, hyaline, smooth, thin-walled, 5-7 x 3,5-4,5 µm. Cystidia absent. Hyphal system dimitic, non-agglutinated. Generative Hyphae thin-walled, septate, without clamps, narrow near the margin, 3,5-6 µm wide, becoming inflated to 7-20 µm wide in the older parts. Binding Hyphae arise as lateral branches from intercalary cells of generative hyphae, branching repeatedly and pseudodichotomously into elaborate, flexuous, thick-walled, binding processes, interwoven with generative hyphae across their direction of growth, 3-12 µm wide and up to 500 µm long. Cultures on malt agar growth is moderately rapid, reaching radii of up to 65 mm in two weeks and covering the plate in 3-4 weeks; optimum temperature 29-30°C; young mycelium appressed to the agar with scattered tufts of cottony mycelium over newest growth, becoming progressively more dense to cottony or woolly and farinaceous, white or Pale ochraceous buff to Salmon pink or Ochraceous buff; reverse unchanged, no odour emitted; no diffusion zones formed on gallic acid and tannic acid agar media but colonies up to 85 mm diam. developing on both after seven days. Advancing Hyphae hyaline, branching, thin-walled, with simple septa, without clamps, 4-6 µm diam. Aerial mycelium hyphae as in the advancing zone, numerous sub-globose to pyriform chlamydospores, 6-16 x 6-8 µm, bourne terminally on narrow much branched, thin-walled hyphae.
Hosts: On trunks, stumps and logs of Abies, Acer, Castanea, Celtis, Eucalyptus, Fraxinus, Cletitsia, Juglans, Larix, Liriodendron, Olea, Picea, Pinus, Prunus, Pseudotsuga, Quercus, Robinia, Schinus, Tamarix, Tsuga and Ulmus.
Disease: Severe red-brown, cubical heart rot with thin sheets of white mycelium present in the cracks. Hyphae are present in the cells some distance beyond the visible signs of attack.
Geographical distribution: World wide in cool and warm temperate regions.
Physiological specialization: Not known.
Transmission: By air-borne spores.
Literature: Pilat, Atl. Champ. Eur. 3: 40, 1936 (synonymy); Davidson, Campbell & Vaughn, Technical Bulletin. United States Depanment of Agriculture 785: 38, 1942; Baxter, Pathology in Forest Practice, 618 pp., 1943; Canwright & Findlay, Decay of timber and its Prevention: 128-130, 1948; Nobles, Canadian Journal of Research C 26: 380. 1948; Corner, Phytomorphology 3: 157, 1953; Overholts, The Polyporaceae of the United States, Alaska and Canada, p. 243, 1953; Browne, Pests and diseases of forest plantation trees, 923 pp., 1968; Hepting, Diseases of forest and shade trees of the United States, 658 pp., 1971.

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