Basis for Listing

Lactarius fuliginellus has been collected twice from a single location in Anoka County, but has not been found elsewhere in the state. It is at the northwestern limits of its known range in Minnesota, and its preferred habitat with Quercus spp. (oaks) and hardwoods in low areas is vulnerable to disturbance from human activity. Lactarius fuliginellus was listed as a special concern species in Minnesota in 1996.

  Description

Mushroom caps are 35-100 mm (1.4-3.9 in.) broad and shallowly depressed. Cap surface is dry and velvety, the color uniform or with paler spots or paler margin, azonate (lacking concentric bands), dark yellowish brown, and may become paler in color or be deep brown in color. Latex (milky fluid) is white and copious. Flesh and gills stain light orange or light yellowish pink (in 15 minutes). Odor is mild. Taste of context mild to mildly disagreeable; latex is mildly bitter. Gills close when young, becoming subdistant (fairly well separated) with age, 4-10 mm (0.2-0.4 in.) broad. Gill color when young is yellowish white, becoming more yellow to pale orange yellow.

Stem is 30-60 mm (1.2-2.4 in.) long, 10-28 mm (0.4- 1.1 in.) thick, with a dry surface that is less velvety than the cap. Stem color is moderate yellowish brown or light brown, with a whitish base. Spores are yellowish white, 7.5-9 x 6.6-8 µm, with a network of high ridges (up to 1.2 µm high). Caulocystidia (large cells on stem surface) are 28-46 x 6-13 µm, clavate to capitate, with a moderate brown content (in 2.5% KOH) and forming a dense turf. Microscopic characters must be examined to reliably separate this species from other similar Lactarius mushrooms. The spores are larger and the caulocystidia are wider and more strongly pigmented than in L. fumosus var. fumosus and var. fumosoides. Important macroscopic characters are the reddish staining, the close to subdistant, broad gills (not narrow and crowded), and the mild to mildly bitter taste.

  Habitat

Lactarius fuliginellus apparently prefers hardwood habitats in areas that are near water or that are periodically inundated. The Michigan type collection was from under hardwoods at the edge of a bog. In Mississippi, it was found in bottomland hardwood forest. The Minnesota population was found in two successive years in Anoka County. The species was located in leaf litter under hardwoods, primarily Quercus spp. and Rubus spp. (blackberry), in a low area that holds water in wet years.

  Biology / Life History

Fully grown fungi disperse spores into the air, which plant themselves in the ground, growing into hyphae, or fungal filaments. Hyphae from two different fungal organisms meet, fuse, and form a mycelium, the filamentous vegetative portion of a fungus (excluding the fruiting/reproductive phase of the life cycle). A small, button-shaped fungus forms, pushes above the ground, and obtains a covering called a veil. When the veil ruptures, an adult fungus grows.

Lactarius fuliginellus is a presumed ectomycorrhizal fungus, one that forms a symbiotic relationship between itself and the roots of oaks and other hardwoods. The fungus forms on the surface of the roots, and is able to absorb water and nutrients, benefiting the plant. The plant provides the fungus with energy-rich sugars manufactured through photosynthesis. Mushroom fruitbodies can be produced in the summer and fall from the perennial underground mycelium. Dispersal is via windborne spores or locally by extension of the mycelium between neighboring trees.

  Conservation / Management

The preferred habitat of lowland hardwoods and the location in Anoka County are vulnerable to disturbance from human activity, including habitat loss and changes in hydrology. Ectomycorrhizal fungi in general are sensitive to nitrogen deposition and other forms of pollution that affect the soil. The distribution of L. fuliginellus in North America may be poorly known because this species is easily mistaken for L. fumosus and can only be reliably separated by microscopic characters.

  Conservation Efforts in Minnesota

Lactarius fuliginellus was collected twice by an amateur mushroom hunter and studied in fresh condition by P.R. Leacock. It was not otherwise recorded during a several year survey of Lactarius in the state (P.R. Leacock, unpublished data), although lowland oak/hardwood forests were not specifically searched. Further surveys are needed to accurately document its distribution and abundance, but based on current knowledge its population size within the state appears to be small.

  References and Additional Information

Hesler, L. R., and A. H. Smith. 1979. North American Species of Lactarius. The University of Michigan Press, Ann Arbor, Michigan. 841 pp.

Smith, A. H., and L. R. Hesler. 1962. Studies on Lactarius - III, the North American species of section Plinthogali. Brittonia 14:432.