Fungi Focus: Kretzschmaria deusta

‘Brittle Cinder’ Kretzschmaria deusta/Ustulina deusta

First named Sphaeria duesta (in 1787 by Franz Hoffman a German naturalist) ‘Brittle Cinder’ was known to be parasitic on the roots and lower trunks of living hardwood trees leaving them prone to sudden and catastrophic collapse.

‘Brittle Cinder’ Kretzschmaria deusta/Ustulina deusta

It became known in more recent years by the scientific name Ustulina vulgaris until 1970 when P.M.D Martin (an African mycologist) transferred the fungus to the genus Kretzschmaria establishing its currently accepted name Kretzschmaria duesta.

It produces wavy-edged cushions (or crusts) clinging to the substrate timber. Initially greyish with white edges, the fruiting bodies turn black and become extremely brittle, hence the name. Whilst its new fruiting bodies start to appear in spring, older blackened fungi can be found on the tree throughout the year.

It affects mainly Oak, Beech and Lime trees and in some cases Acers and other hardwood trees.

Kretzschmaria duesta cannot always be easy to spot as the tree can look healthy. The fruiting bodies tend to develop between the root buttresses so unless the surveyor looks closely (or the fruiting bodies are obvious) this ‘tree killer’ can be missed.

Recently Mark Kirk (ND Horticulture FdSc Arborculture), one of Beechwood Trees Contract Managers, came across a very large, mature Beech tree in Halesowen which was identified as having Brittle Cinder.

The tree had to be subsequently dismantled due to its location in a public space and the high risk of failure which this particular fungus brings…

Picture: Beechwood’s Arborist Alex Hall dismantling
the affected Beech tree in Halesowen in February 2019.




As a tree owner, it is always a good idea to have a good basic knowledge of tree fungi, its identification, effects and management, but if you are unsure then please get in touch and we would be happy to help.


Jim Pennington
Beechwood Trees and Landscapes Ltd
Compliance Manager


Further reading:

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008.

David Lonsdale ‘Principles of Tree Hazard Assessment and Management’ 1999