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Species Information
Summary: The short-stemmed fruitbodies erupt by the thousands in blackened areas of standing and fallen dead aspen where bark has sloughed off, (Callan 1998).
Encoelia pruinosa is the most damaging primary canker pathogen of aspen in northern and central BC, and in the Rocky Mountain region of the United States: in CO more than half the tree mortality in commercially managed aspen stands is attributed to sooty bark cankers, (Callan). Collections were examined from ID, and also ON, CO, MI, NH, NY, (Davidson).
Upper surface: 0.1-0.3cm across, saucer-shaped; spore bearing upper surface brown; when weather dry, outer margins curl inward and the fruitbodies roll into grayish brown, rough-surfaced, longitudinally split tubes, (Callan), reaching 0.3-0.4cm across, cup-shaped with mouth at first constricted, when dry becoming boat-shaped or angular; brown to brownish black, the margin slightly crenate [scalloped], (Seaver)
Underside: grayish brown; rough, (Callan), brown to brownish black; covered with a white granular coat, (Seaver)
Stem: short (Callan)
Microscopic: spores 8-11 x 2-3 microns, sausage-shaped, colorless; asci 8-spored, 40-55 x 4-5 microns on average, (Callan), spores 8-10 x 2 microns, allantoid [curved sausage-shaped]; asci 8-spored, reaching a length of 55 microns and a width of 4-5 microns, narrow-clavate; paraphyses filiform, very slender, enlarged in upper part, with dark brown tips, (Seaver)
Habitat / Range
in BC known only from Populus tremuloides (Trembling Aspen), but reported to occur occasionally on P. trichocarpa (Black Cottonwood) and P. balsamifera (Balsam Poplar) in other areas, (Callan), on trunks of Populus, gregarious, occurring in large numbers under outer aspen bark, which rolls back exposing large blackened areas on which fruitbodies are seated, (Seaver), aspen is associated with a number of canker diseases: this one is common in most areas of the central Rocky Mountains, rather uniformly distributed through older or mature stands, seldom found in young stands up to 60 years, the bark over the cankered area usually remaining intact and tightly attached even after the tree dies, the cankers not being conspicuous but sometimes taking on "a slightly target-like appearance where part of the outer white surface has flaked away in a somewhat zoned pattern exposing part of the blackened inner bark", except for the thin white outer layer the bark becomes a uniform sooty black, fruitbodies usually develop abundantly on the old diseased black bark or under the loosened white surface layer, the fruitbodies being present in all seasons, (Davidson)
Similar Species
in addition to Encoelia furfuracea, Encoelia fascicularis has been recorded at least from BC (collection at Pacific Forestry Centre in Victoria): Seaver(2), who reports E. fascicularis as Cenangium populneum on Populus or more rarely Fraxinus from CO, IA, KS, MA, and Europe, differentiates it by cespitose (as opposed to scattered), non-pruinose fruiting bodies.
