Lactarius deterrimus, also known as false saffron milkcap or orange milkcap, is a species of fungus in the family Russulaceae. The fungus produces medium-sized fruit bodies (mushrooms) with orangish caps up to 12 centimetres (4+1⁄2 inches) wide that develop green spots in old age or if injured. Its orange-coloured latex stains maroon within 30 minutes. Lactarius deterrimus is a mycorrhizal fungus that associates with Norway spruce and bearberry. The species is distributed in Europe, but has also found in parts of Asia. A visually similar species in the United States and Mexico is not closely related to the European species. The fruit bodies appear between late June and November, usually in spruce forests. Although the fungus is edible—like all Lactarius mushrooms from the section Deliciosi—its taste is often bitter, and it is not highly valued. The fruit bodies are used as source of food for the larvae of several insect species. Lactarius deterrimus can be distinguished from similar Lactarius species by difference in the mycorrhizal host or latex colour.
Taxonomy Although the fungus is one of the most common in Central Europe, the species was not validly described until 1968 by German mycologist Frieder Gröger. Before this, L. deterrimus was regarded as a variety of L. deliciosus (L. deliciosus var. piceus, described by Miroslav Smotlacha in 1946). After Roger Heim and A. Leclair described L. semisanguifluus in 1950, this fungus was referred to as the latter. L. fennoscandicus was separated from L. deterrimus in 1998 by Annemieke T. Verbeken and Jan Vesterholt and was classified as a separate species. The epithet of deterrimus is Latin, and was chosen by Gröger to highlight the poor gustatory properties of the mushroom, such as the bitter aftertaste and often heavy maggot infestations. The superlative of "dēterior" (meaning less good) means "the worst, the poorest". The mushroom is commonly known as the "false saffron milkcap". Several molecular phylogenetic analyses show that L. deterrimus, L. sanguifluus, Lactarius vinosus and L. fennoscandicus form a group of related species, which might include the North American species L. paradoxus and L. miniatosporus. Although L. deliciosus var. deterrimus qualifies as synonym for L. deterrimus, the families that had been characterized in North America as Lactarius deliciosus var. deterrimus are not closely related with the European types. They also seem not to form a monophyletic group. Lactarius deterrimus belongs to the section Deliciosi of the genus Lactarius. According to molecular phylogenetics studies, this section forms a definite phylogenetic group within the milk cap relatives. Deliciosi species mainly have an orange or reddish-coloured latex and taste mild to slightly bitter. They are strict mycorrhizal associates of conifers. The next closest relative of L. deterrimus is L. fennoscandicus.
Description
Macroscopic characteristics
The cap is 3 to 10 cm (1 to 4 in), rarely up to 12 cm (4+1⁄2 in) wide and more or less centrifugal-shaped and round. It is at early stage convex, furled on the edge, and depressed in the centre. Later it is flat, funnel-shaped, and depressed. The cap skin is bare, greasy in moist weather and slightly shiny when dry. The cap is tangerine to orange-brown, darker zoned towards the edges and dulls mainly yellow-brown. In old age or after cold or frost it changes the colour more or less to dirty greenish or green-spotted. The dense, bow-like lamellae are pale-orange to pale-ochre and on the stipe basifixed or slightly decurrent. They are brittle and intermixed with shorter lamellulae (short gills that do not extend fully from the cap margin to the stem) as well as partly forking near the stem. In old age or in cases of injury they receive initially dark red, later grey green spots. The spore print is pale ochre.
The mainly long and cylindrical stipe is reddish orange. It is 4 to 8 cm (1+1⁄2 to 3 in) (rarely 10 cm (4 in)) long, 1 to 1.5 cm (3⁄8 to 5⁄8 in) wide and barely foveate or blotchy. On the basis it is often slightly thickened or pompous and becomes hollow inside. A bloomy circular zones is found on the lamella disposition. The milk is first carrot-red and becomes a maroon colour within 10 to 30 minutes. The brittle and pale-yellowish flesh is often infested with maggots. If cut or injured it becomes, as the milk, first carrot-red, then maroon and within hours dirty green. The fruit body smells harsh, fruit-like and first tastes mild, but then slightly resinous-bitter and nearly spicy or somewhat astringent.
Microscopic characteristics The rotund to ellipsoid spores are 7.5–10 μm long and 6–7.6 μm wide. The surface ornamentation extends to 0.5 μm high and is mainly from warts and short, wide ridges, which are linked through few fine lines to form an incomplete net (reticulum). The suprahilar area, a distinctly limited zone above the apiculus, is weakly amyloid. Basidia (spore-bearing cells) are four-spored and measure 45–60 × 9.5–12 μm. They are roughly cylindrical to somewhat club-shaped and often have an oil droplet or a granular body. The sterigmata are 4.5–5.5 μm long. The thin-walled pleurocystidia are sparse, but somewhat common near the gill edge. They are protruded and are 45–65 μm long and 5–8 μm wide, they are sometimes smaller near the gill edge. Nearly spindle-shaped, they are often straightened or constricted like a string of pearls at the apex. The body is often fine and grained. Pseudocystidia are largely present. They are 4–6 μm wide and are sometimes protruded, but are often shorter than the basidioles (basidia in the early developmental stage). The basidioles are cylindric to spiral and have an ochre-coloured substance, similar to the laticifers. Near the top they are, however, almost hyaline (transparent). The gill edge is usually sterile and has a few to many cheilocystidia. The thin-walled cheiloleptocystidia are 15–25 μm long and 5–10 μm wide. They are almost club-shaped or irregularly shaped and transparent, and often contain a granular material. The cheilomacrocystidia are also thin-walled and measure 25–50 μm long and 6–8 μm wide. They are slightly spindle-shaped and often have a tip resembling a string of pearls; their interior is hyaline or granular. Laticifers are abundant, striking and body is ochre coloured. The cuticle of the cap is an ixocutis, whereby the hyphae are linked in a jellylike matrix, that can swell up in moisture to become heavily slimy.
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