Fungi spotlight: Daedalea quercina

For this spotlight on wood-decay fungi, I thought I would turn attention towards the oak maze-gill. This fungus is rather attractive, and certainly variable in its morphology – I have seen it as a large bracket and also as a tiny ‘hoof-shaped’ sporophore (in the former, it is certainly much nicer on the eye).

Occurrence of Daedalea quercina is predominantly on Quercus spp. (oaks), though Fagus spp. (beech) and Castanea sativa (sweet chestnut) have also been observed to act as hosts for this fungus at times. Curiously, in the USA, coniferous species have been observed as hosts, though I am unsure of whether there is much evidence of this in any other parts of its natural range.

Colonisation occurs via dead attached branches, damaged stems, fallen wood, or a stump, and is limited largely to the heartwood – despite this, sapwood colonisation can occur, though usually the oak maze-gill can be seen to have colonised dead sections of its host (or an entire dead structure).

A view of an oak maze-gill bracket, which measures around 30cm in width, upon the end of an oak log.

With regards to its mode of decay, it is a slow-acting but intense brown rot. Such rot causes the wood to become brittle (as the cellulose is removed), thereby leaving the structure prone to brittcle fractring during loading events. As it is typically found upon (standing or fallen) deadwood however, its significance is ultimately rather limited. Issues can however arise from decay of dead branches within the crown, particularly if they are large, or where colonisation of an entire living or dead host can be observed – in such cases, cavities may form throughout the main stem and leave the structure prone to failure. Where colonising Taxodium distichum, Daedalea quercina presence has in fact been observed to lead to exceptionally severe internal decay.

Here, we can see how the fungus has produced sporophores – all the way up into the crown – at the interface between functional and dysfunctional wood.

However, rarely is presence of Daedalea quercina grounds for removal, though dead material within the crown should be removed if the target area is significant. The condition of standing hosts with extensive decay should be routinely monitored, and made safe where appropriate (via monolithing, felling, or otherwise).

Suggested reading list:

Baietto, M. & Wilson, A. (2010) Relative in vitro wood decay resistance of sapwood from landscape trees of southern temperate regions. HortScience. 45 (3). p401-408.

Glaeser, J. & Smith, K. (2010) Decay fungi of oaks and associated hardwoods for western arborists. In Winter Arborist, Winter 2010. p32-46.

Lonsdale, D. (1999) Principles of Tree Hazard Assessment and Management (Research for Amenity Trees 7). London: HMSO.

Luley, C. (2005) Wood Decay Fungi Common to Urban Living Trees in the Northeast and Central United States. USA: Urban Forestry LLC.

Mattheck C., Bethge, K., & Weber, K. (2015) The Body Language of Trees: Encyclopedia of Visual Tree Assessment. Germany: Karlsruhe Institute of Technology.

Schmidt, O. (2006) Wood and Tree Fungi: Biology, Damage, Protection, and Use. Germany: Springer.

Sunhede, S. & Vasiliauskas, R. (1996) Wood and bark inhabiting fungi on oak in Lithuania. Baltic Forestry. 2 (2). p23-27.

Weber, K. & Mattheck, C. (2003) Manual of Wood Decays in Trees. UK: The Arboricultural Association.

Daedalea quercina upon a large oak log

Farmers may likely resort to placing large pieces of timber at the boundary of their land, in an attempt to stop vehicles driving onto their property and using it for either a temporary home (as travellers may do), or otherwise. Not only is such a tactic incredibly effective at halting vehicular trespass, but also more ecologically beneficial than constructing, for instance, a man-made fence.

On this oak log, we can see that Daedalea quercina (oak mazegill) has colonised and subsequently produced a sporophore. I first noticed this earlier in the year during an ‘inactive’ phase, though recently it has sprung into life again. I therefore took the opportunity to take some photos and a small sample, of which the results are below.

The oak mazegill, according to Mattheck et al. (2015), can be both parasitic and saprophytic, though I have only ever seen it act saprophytically. It induces a brown rot of the heartwood by preferentially degrading the cellulose, and is principally found on oak (though sweet chestnut may also be a host).

A view of the entire bracket, which measures around 30cm in width, upon the end of an oak log.

A closer inspection reveals the wonderful texture of the bracket.

Here we can see where this fungus gets its common name.

A small sample taken from the bracket reveals the inner workings of the bracket, and also shows how much new growth has been laid down in this growing period (note the sudden transition between dark brown and beige).

Cutting the sample in half and folding it out produces a very lovely symmetrical image, if nothing else!