Gyrodon merulioides

Description

This common bolete was long thought to be mycorrhizal with ash but it is now thought to be dependant on an aphid associated with this tree. Irregular in shape and somewhat variable in color (brown, olivaceous brown, tarnished brass color), it has a very short lateral stipe and shallow, honey-comb like pores. It forms sclerotia in culture and nature, as do other members of this genus, for example, Gyrodon monticola Singer (Halling, 1989).

The fact that Gyrodon merulioides (syn. Boletinellus meruliodes) is invariably associated with ash makes it easy to identify. In the symbiotic relationship mentioned above, the vegetative body of the fungus (or mycelium) forms little knots of tissue (called "sclerotia") that surround and protect the aphid. In return, the aphid produces a sugary solution (referred to as "honeydew") that is utilized by the fungus.

The fruit bodies are edible but of low quality, with an acidic taste.

Common names: Ash Tree Bolete.

Mushroom Identification

1. Ecology

   Found under green ash trees and other ash trees; probably involved in symbiosis with the leafcurl ash aphid, Meliarhizophagus fraxinifolii; growing alone, scattered, or gregariously; summer and fall; widely distributed in eastern North America (perhaps also occurring in the southwest).

2. Cap

   5-20 cm, irregular (nearly convex when young, becoming wavy and nearly vase-shaped, or more or less flat); light to dark yellowish-brown, or sometimes reddish-brown; dry, tacky when wet; bald; soft and leathery; sometimes bruising darker brown.

3. Pore Surface

   Pores elongated radially, sometimes appearing almost like gills, with many cross-veins; tubes shallow; running down the stem; yellow to olive, bruising brownish to olive to almost blue (sometimes not bruising); tube layer not easily separable.

4. Stem

   2-4 cm long; 0.5-2.5 cm thick; usually not central (sometimes nearly lateral); yellowish above, colored like the cap (or darker) below; sometimes bruising darker brown or, near the base, blue.

5. Flesh

   Whitish to yellowish or yellow; sometimes bruising blue when sliced, especially in the base of the stem and/or just above the tubes.

6. Odor and Taste

   Odor fragrant or not distinctive; taste not distinctive.

7. Chemical Reactions

   Ammonia purplish red on cap surface; orangish to negative on flesh. KOH dark orange on cap surface; orange on flesh. Iron salts pale orange to negative on cap; bluish-gray on flesh.

8. Spore Print

   Olive brown.

9. Microscopic Features

   Spores 7-10 x 6-7.5 µ; smooth; ellipsoid. Pleurocystidia to about 35 x 10 µ; lageniform. Pileipellis a cutis of mostly erect, cylindric elements 6-9 µ wide. Clamp connections present.

Uses

Gyrodon merulioides gets mixed reviews when it comes to edibility. Some websites list it as edible while others say it inedible. Within the edible group, the consensus seems to be that the mushroom is not particularly good (although it might be better when very young). In eastern North America, the general rule for boletes is: don’t eat it if it has red pores, stains blue, or is too bitter. The Ash Tree Bolete does stain blue (at least sometimes), so it fails this test.

History

The species was first described as Daedalea merulioides by Lewis David de Schweinitz in 1832, from collections made in Salem. William Alphonso Murrill transferred the species to the genus Boletinellus in 1909. Rolf Singer classified it in the genus Gyrodon, but it is not closely related to that genus genetically.

Photo sources:

Photo 1 - Author: Anita Gould (Attribution-NonCommercial 2.0 Generic)

Photo 2 - Author: Rocky Houghtby (Attribution 2.0 Generic)