What You Should Know
Ustulina Deusta is a pathogenic and saprophytic wood decay fungi, found on broadleaved trees including beech, lime, maple, and horse chestnut. It causes soft rot and decays the stem base and/or roots. The resulting brittle fracture has a ceramic-like fracture surface.
The fruiting bodies persist all year and their appearance is that of a coin-sized asphalt spattering of domed lumpy crusts, brittle like charcoal, usually between the root buttresses. New fruiting bodies formed in the spring are flat and whitish-gray.
It is a soft rot decay fungus that is generally regarded as affecting the root and butt areas of the tree (Strouts and Winter 1994, Webber and Mattheck 2001, Schwarze et al 2003). However, Guglielmo (2012) isolated the fungus present several meters up the trunk of trees in their study.
The spring version of Kretzschmaria deusta is asexual, producing conidia but not actual spores; it appears as a tough gray patch with a powdery surface and white edges. The later, sexual stage produces spores that look surprisingly like the spores of Xylaria species—and in fact Kretzschmaria and Xylaria are closely related.
Other names: Brittle Cinder, Burn Crust.
Kretzschmaria deusta Mushroom Identification
Saprobic on the living or dead wood of hardwoods; causing a white rot; often found at the bases of trees; spring through fall; common and widely distributed east of the Rocky Mountains.
Springtime, Asexual Stage
Spreading in patches 2–9 cm across, irregular in outline; surface dull gray and dusty; dust rubbing off easily to expose a brownish, bumpy surface; white and smooth along the margin; 1–2 mm thick; flesh tough, watery whitish to brownish, developing embedded black dots; with a thin black line just under the upper surface.
Summertime, Sexual Stag
Surface black, hard, bumpy, and lumpy, forming a crust over a cavity of whitish, powdery flesh that disintegrates to create a hollow structure.
Conidia 4–7.5 x 2–3 µm; subfusiform to elongated-lacrymoid; smooth; hyaline in KOH; produced on cylindric elements 25–45 x 2–4 µm. Spores 30–32 x 8–9 µm; fusiform; with a pale, longitudinal germ slit that does not extend to the ends of the spore; smooth; very dark brown to black in KOH.
Kretzschmaria deusta Taxonomy and Etymology
The scientific name Sphaeria Deusta was given to this ascomycetous fungus in 1787 by German naturalist George Franz Hoffmann (1761 - 1826).
Brittle Cinder was known until recently by the scientific name Ustulina vulgaris, but in 1970 South African mycologist P. M. D. Martin (biographical details unknown to us at present) transferred this ascomycete fungus to the genus Kretzschmaria, establishing its currently-accepted scientific name Kretzschmaria deusta.
Synonyms of Kretzschmaria deusta include Sphaeria deusta Hoffm., Sphaeria maxima Bolton, Hypoxylon ustulatum Bull., Nemania deusta (Hoffm.) Gray, Stromatosphaeria deusta (Hoffm.) Grev., Hypoxylon deustum (Hoffm.) Grev., Ustulina vulgaris Tul. & C. Tul., and Ustulina deusta (Hoffm.) Lind.
The specific epithet deusta means burned, a reference to the cinder-like appearance and texture of mature fruitbodies of this wood-rotting fungus.
Kretzschmaria deusta Treatment
More often than not, trees infected with Kretzschmaria deusta are recommended to be felled as soon as possible because of the rapid deterioration of trees affected by this fungus.
If you catch the fungus in its early stages it may be possible to destroy any arisings to prevent it from spreading. But please check with a professional before destroying.
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Photo 2 - Author: Arthur Gelling (Creative Commons Attribution 4.0 International)
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