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Species Information
Summary: Features include 1) tiny, circular, black or yellow fruitbodies with the spore-bearing surface flat or concave and the margin slightly raised, 2) consistency hard (fleshy when moist), 3) absent stem, 4) erumpent growth on Douglas-fir branches and stems, 5) the production of a yellowish brown color when specimens are mounted in KOH, and 6) microscopic characters. This species is a causal agent of phloem necrosis in Douglas-fir.
Dermea pseudotsugae was described from specimens from the interior of BC. It occurs on BC coast but usually only in the conidial state. It has caused serious damage to Douglas-fir plantations in northern CA, (Funk(4)).
Upper surface: apothecia [sexual fruitbodies] 0.1-0.16cm across, 0.02-0.04cm high, circular or slightly undulate, black or yellow; spore-bearing surface flat or concave, black or yellow; margin slightly raised; conidial fruitbodies 0.03-0.1cm across, 0.02-0.05cm high, "immersed or partially erumpent, circular or somewhat flattened", "yellow to black, tearing open widely at the top, usually with a single, simple cavity", (Funk(2)), conidial fruitbodies yellow (Funk(4))
Flesh: consistency hard, fleshy when moist, (Funk(2))
Underside: black or yellow (Funk(2))
Stem: sessile [without a stem] (Funk(2))
Chemical Reactions: apothecia mounted in dilute KOH produce a yellow brown discoloration in the liquid (Funk(2))
Microscopic: spores 16-28 x 4-7 microns, elliptic, straight or slightly bent, colorless, continuous to 3-septate; asci 8-spored, 80-150 x 9-14 microns, cylindric to clavate, short-stemmed, pore stains blue in iodine; paraphyses "longer than the asci and agglutinated to form an epithecium", filiform [thread-like], colorless, "septate, simple or branched, slightly swollen at the tips"; macroconidia 42-56 x 3-4 microns, sickle-shaped, colorless to pale yellow, 0-3-septate, microconidia 8-14 x 1-2 microns, filiform, curved or bent, colorless; conidiophores 18-30 microns long, colorless, simple or branched (Funk(2))
Habitat / Range
"erumpent, separate, gregarious", on branches and stems of Pseudotsuga menziesii [Douglas-fir], late August and September, conidia produced somewhat earlier in the year, many of the apothecia overwintered "and in the spring were found to contain ascospores which did not appear to be viable", (Funk(2))
Similar Species
Dermea balsamea also has relatively large (for Dermea), yellow to black apothecia and conidia with sharply pointed ends, exceeding 35 microns long, and both grow on conifers, but the fruiting structures of Dermea balsamea are larger: apothecia reach 0.25cm whereas those of D. pseudotsugae rarely exceed 0.15cm, the maximum length of the spores in D. balsamea is 7 microns more than in D. pseudotsugae, and the maximum length of the macroconidia in D. balsamea is twice the length in D. pseudotsugae, (Funk(2)). Dermea grovesii has reddish brown apothecia, (Funk(2)).
