Lactarius pseudomucidus — Slimy milk cap

Slimy milk cap

Slimy milk cap1, photograph by Adolf Ceska.

Slimy milk cap

Slimy milk cap7, one sliced to show gill attachment, photograph by Adolf Ceska.

Slimy milk cap

Slimy milk cap8, photograph by Patrik Inderbitzin.

Not edible


Gills: Attached or slightly decurrent, white to cream
Spore print: White to pale yellow

Odour: Indistinct.
Cap: 2–10 cm in diameter, convex at first, spreading out and developing a central depression. The colour is dark brownish grey, darkest in the centre. The surface is smooth, and viscid when wet. The flesh tastes acrid.
Gills: Crowded, attached or slightly decurrent, white and a bit greyish, and staining yellow to brown from the latex. The gills taste very acrid.
Latex: Milk-white and thin, staining the gills yellow to brown.
Stem: 3–10 cm long x 0.5 –1 cm wide, straight and cylindrical, hollow. The colour is pale grey-brown, a bit streaked, often palest at top and bottom. The surface is viscid or tacky.
Ring or veil: None.
Cup: None.
Spores: 7–9 x 6–7 µm, with a network of ridges.
Habitat: In coastal and low-elevation conifer forests, in particular under western hemlock (Tsuga heterophylla) and grand fir (Abies grandis). Ectomycorrhizal.
Geographical range: Western North America: from Alaska to central coastal California, eastwards into Idaho.

Lactarius kauffmanii is another grey milk cap with an acrid taste. It differs from the slimy milk cap in that the latex, though it starts white, discolours to become greyish or even greyish green as it dries and it stains the gills tan. The gill colour is not as white as in L. pseudomucidus and the stem is never viscid, though it can be a bit tacky.

Milk caps sometimes cause gastrointestinal upsets6. Although the slimy milk cap has not been implicated in causing illness, its flavour is unappealing and like other acrid/hot tasting species, it may cause stomach upsets.

Treatment: Contact your regional Poison Control Centre if you or someone you know becomes ill after eating milk caps. 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.

1
Specimen Lactarius pseudomucidus Ceska 2016 MO 259681.
2
Siegel, N. & Schwarz, C. Mushrooms of the Redwood Coast. A Comprehensive Guide to the Fungi of Coastal Northern California. Ten Speed Press, Berkeley, California (2016).
3
Bessette, A. E., Harris, D. B. & Bessette, A. R. A field identification guide to the genus Lactarius. Syracuse University Press, Syracuse, New York (2009).
4
Hesler, L. R. & Smith, A. H. North American species of Lactarius. The University of Michigan Press, Ann Arbor, Michigan (1979).
5
Trudell, S. & Ammirati, J. F. Mushrooms of the Pacific Northwest. Timber Press, Portland, Oregon (2009).
6
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).
7
Specimen Lactarius pseudomucidus UBC F25291 MO 84266, GenBank #MH718196.
8
Specimen Lactarius pseudomucidus UBC F14290, GenBank #AY228358.