Scleroderma bovista — Potato earthball

Card image cap

Potato earthball2, photograph by Ludovic Le Renard.

Poisonous

Gills: Non-gilled
Spore mass: Purplish black


Odour: None or mild when fresh, unpleasant when old.
General form: Potato-shaped 1.5-8 cm in diameter, yellowish brown, mostly smooth but with small scales and cracks. White thread-like strands of mycelium often radiate from the base.
Outer layer, "peridium": 1-3 mm thick, tough, whitish in cross section.
Inner tissue, "gleba": Initially white but soon turning dark purplish grey, to brown or black.
Spores: 9.5-16 (-19.5) µm including the ornamentation, which is a network of interconnected ridges and spines 1.6-3.5 µm tall; spores are dark brown or black.
Spore release: The outer wall dries and cracks open to release spores (unlike puffballs that open with a rounded pore).
Habitat: growing on soil, mostly above ground. Associated with various trees including red oaks (Quercus spp.), birch (Betula spp.), pines (Pinus spp.) and Douglas fir (Pseudotsuga menziesii)1; ectomycorrhizal.
Geographical range1: Widely distributed in the Northern Hemisphere and likely introduced to the Southern Hemisphere along with its host trees.

To distinguish a poisonous earthball from a puffball (Lycoperdon and similar genera), press the outer surface. An earthball is firm; a puffball feels more like a marshmallow. Cut the ball in half from top to bottom. An earthball has a peridium or rind that is ~2 mm thick. The peridium of a puffball is much thinner–only about as thick as the shell of an egg. The inside of both earthballs and puffballs may be white or yellowish when young, but the earthball's interior soon turns dark brown to almost black while the puffball turns olive brown.

Unlike an edible truffle (Tuber species), earthball species have no odour when fresh and a revolting odour when old. Also unlike truffles (Tuber species), the earthball's inner tissue is uniformly coloured, not marbled with white veins. Tuber species do not develop a powdery spore mass.

Other Scleroderma species, recognizable as earthballs due to their thick rinds and blackish spore masses are also found in our region, and they are also poisonous.

Poisonous
 

Toxins: Unidentified gastrointestinal irritants.

Symptoms: Time of onset, 10 min to 5 hours5. Vomiting, stomach cramps, watery diarrhea becoming bloody, and muscle rigidity in severe cases6.

Treatment: Contact your regional Poison Control Centre if you or someone you know is ill after eating any earthballs. Poison Centres provide free, expert medical advice 24 hours a day, seven days a week. If possible, save the mushrooms or some of the leftover food containing the mushrooms to help confirm identification.

Poison Control:
British Columbia: 604-682-5050 or 1-800-567-8911.
United States (WA, OR, ID): 1-800-222-1222.

Cases of poisoning by Scleroderma species:
Mistaking earthballs for truffles or puffballs has resulted in numerous poisonings along the west coast and across North America5,7.

1
MyCoPortal. Mycology Collections Portal, <http://mycoportal.org/portal/collections/harvestparams.php> accessed March 2018.
2
Specimen Scleroderma bovista UBC F32077, GenBank #MH718214.
3
Arora, D. Mushrooms Demystified. Ten Speed Press, Berkeley, California (1986).
4
Ramsey, R. Trial field key to the species of Sclerodermataceae in the Pacific Northwest. <http://www.svims.ca/council/Sclero.htm> (2003).
5
Beug, M. W., Shaw, M. & Cochran, K. W. Thirty-plus years of mushroom poisoning: Summary of the approximately 2,000 reports in the NAMA case registry. McIlvainea 16, 47-68 (2006).
6
Stevenson, J. A. & Benjamin, C. R. Scleroderma poisoning. Mycologia 53, 438-439, doi:10.2307/3756589 (1961).
7
Beug, M. W. Mushroom poisoning in North America, summary of voluntary reporting and news articles for 2015 and 2016. McIlvainea <http://www.namyco.org/toxicology_reports.php> 25 (2016).