Armillaria tabescens (Scop.) Emel - Ringless Honey Fungus

Distribution - Taxonomic History - Etymology - Identification - Toxicity - Reference Sources

Armillaria tabescens - Ringless Honey Fungus

Taxonomy

Phylum: Basidiomycota

Class: Agaricomycetes

Order: Agaricales

There are many forms of Honey Fungus, and in the past they all shared the scientific name Armillaria mellea. Nowadays it is generally accepted that there are several distinct species, one of which, Armillaria tabescens, does not have a stem ring. Armillaria tabescens is on average a little smaller and usually darker than Armillaria mellea.

Like Armillaria mellea, this parasitic fungus occurs on broad-leaf trees, and oaks in particular.

Distribution

Uncommon and localised in Britain and Ireland, the Ringless Honey Fungus occurs widely throughout central and southern mailnand Europe but is a rare find or not known to occur in some northern countries.

Taxonomic history

This species was described in 1772 by Joannes Antonius Scopoli (1723 - 1788), who named it Agaricus tabescens. (In those days most gilled fungi were initially placed in a giant Agaricus genus, now redistributed to many other genera.) Ringless Honey Fungus was moved into its present genus in 1921 by the French mycologist Louis Emel (dates unknown).

Synonyms of Armillaria tabescens include Agaricus tabescens Scop., Lentinus caespitosus Berk., Pleurotus caespitosus (Berk.) Sacc., Clitocybe tabescens (Scop.) Bres., Armillaria mellea var. tabescens (Scop.) Rea & Ramsb., and Armillariella tabescens (Scop.) Singer.

Etymology

The specific epithet tabescens means 'wasting away' and is a probably reference to the rapid collapse of the fruitbodies of this warm-climate species.

Toxicity

Although all Armillaria species were for many years generally considered edible when thoroughly cooked, those members of the honey fungus group (including Armillaria mellea) that occur on hardwoods are now considered suspect, as cases of poisoning have now been clearly linked to eating these species. We therefore recommend that this species is not collected for the pot.

Identification guide

	Cap 4 to 8cm in diameter; colour ranging from ochre-brown to red-brown, usually with a darker area towards the centre. The cap flesh is white and firm. Initially deeply convex with inrolled margins, the caps flatten and often become centrally depressed with slightly wavy, striated margins. Fine dark scales cover the young caps, often creating a zoned effect, most noticeably towards the centre.
	Gills The adnate or weakly decurrent gills are crowded and initially pale flesh coloured, gradually becoming pinkish-brown at maturity. Stem When young, the stems are white, turning yellow or yellowish-brown and finely woolly as the fruitbody matures. 5 to 14mm in diameter and 5 to 14cm tall; tapering at base where several stems are fused together (caespitose). The stem flesh is whitish and there is no ring.
Spore print	White or very pale cream.
Odour/taste	Astringent odour and bitter taste.
Habitat	Parasitic and/or saprobic on the roots and occasionally the lower trunk area of broad-leaf trees, most commonly oak trees (including evergreen as well as deciduous oaks).
Season	June to November in Britain and Ireland.
Similar species	Armillaria mellea, commonly referred to as Honey Fungus, is larger and paler but otherwise quite similar; however, it has a stem ring. Armillaria gallica has a bulbous stem and a fleeting cobweb-like ring that becomes merely a yellowish ring zone at maturity. Pholiota squarrosa is generally similar in colour and covered in scales; it retains an in-rolled margin, the gills turn uniformly rusty-brown, and it has a radish-like smell and taste.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2011.

Pegler DN. (2000). 'Taxonomy, nomenclature and description of Armillaria'. In Fox RTV. Armillaria Root Rot: Biology and Control of Honey Fungus. Intercept Ltd. pp. 81–93. ISBN 1-898298-64-5.

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

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.