Major Groups > Mycotrophs > Boletus parasiticus
Major Groups > Boletes > Boletus > Boletus parasiticus


Boletus parasiticus

[ Basidiomycetes > Boletales > Boletaceae > Boletus . . . ]

by Michael Kuo

Here is one bolete species, at least, that is a cinch to identify: it parasitizes the earthball Scleroderma citrinum, growing right out of its body! There are many other examples of parasitism in the mushroom world (see the key to mycotrophs for examples), but none of the other cases involves a bolete popping out of a puffball.

If you were to separate Boletus parasiticus from its host, however, you would have a pretty non-descript little bolete with a yellowish brown cap and a honey-yellow pore surface. In this case the application of a drop of KOH on the stem would probably help distinguish the mushroom (see below), as would the presence of many tiny, dark fibers on the stem, which almost look like the scabers found in Leccinum species.

How does this mushroom survive? What I mean is, after it has distributed its spores, what happens to them? Do they float around in the air currents for years, waiting for earthballs to appear so they can dive-bomb and germinate? Do they land in substrate that contains earthball mycelium, then camp out, waiting for the earthball organism to make fuiting bodies? Or does Boletus parasiticus parasitize Scleroderma citrinum even in the mycelium--do the mycelia of the two species grow together?

Xerocomus parasiticus is a synonym, as is Pseudoboletus parasiticus.


Ecology: Parasitic on Scleroderma citrinum, which is mycorrhizal with hardwoods and conifers; most frequently found, in my experience, when the host is growing in mossy areas in low-lying eastern hemlock bogs; growing alone or in small clusters; summer and fall; fairly widely distributed in eastern North America but most common in the Appalachian Mountains.

Cap: 2-8 cm; convex, becoming broadly convex; dry; smooth; margin rolled under when young; yellowish brown to olive.

Pore Surface: Yellow to olive; not bruising but sometimes staining slowly dirty brown to reddish brown; pores 1-2 mm wide; tubes to 6 mm deep.

Stem: 3-6 cm long; 0.5-1.5 cm thick; more or less equal; often curved; dry; solid; colored more or less like the cap; covered with tiny yellowish brown fibers.

Flesh: Pale yellow; not staining on exposure.

Odor and Taste: Not distinctive.

Chemical Reactions: Ammonia red to reddish brown on cap surface. KOH red to reddish brown on cap surface; orange on flesh; cinnabar orange on stem surface. Iron salts olive on flesh.

Spore Print: Olive brown.

Microscopic Features: Spores 12-18.5 x 3.5-5 µ; smooth; subfusoid.

REFERENCES: Bulliard, 1790. (Fries, 1821; Saccardo, 1888; Coker & Beers, 1943; Singer, 1945; Snell & Dick, 1970; Smith & Thiers, 1971; Smith, Smith & Weber, 1981; Weber & Smith, 1985; Phillips, 1991/2005; Lincoff, 1992; Both, 1993; Barron, 1999; Bessette, Roody & Bessette, 2000; Roody, 2003; McNeil, 2006; Miller & Miller, 2006; Kuo, 2007; Binion et al., 2008.) Herb. Kuo 09029503, 08180606.

This site contains no information about the edibility or toxicity of mushrooms.


Boletus parasiticus

Boletus parasiticus

Boletus parasiticus

Boletus parasiticus

Boletus parasiticus

Boletus parasiticus
A pair of parasites: Hypomyces chrysospermus attacking Boletus parasiticus attacking Scleroderma citrinum.

© MushroomExpert.Com

Cite this page as:

Kuo, M. (2003, February). Boletus parasiticus. Retrieved from the MushroomExpert.Com Web site: