October Salt Spring Island Fungus of the Month: Lactarius rubrilacteus

When cut or damaged, fungi in the Lactarius genus ooze a sticky opaque liquid intended to make the mushroom harder for insects to chew on. This gives them the common name of "milkcaps".  Usually the "milk" is white, but in some species it can be yellow, orange, or blue. Our extra-spooky fungus of the month, Lactarius rubrilacteus, appears in October and bleeds a red latex. 

observation by spinyurchin

Lactarius rubrilacteus is usually orangey brown, but may have blueish green blotches. It is a medium sized mushroom found in forested areas or under trees. But by far the easiest way to identify it is to break the cap or cut the gills and see if it oozes red; similar-looking Lactarius species have white or orange latex.

observation by dd45988

Milkcaps, like their cousins the Russulas, are mycorrhizal: they colonize the roots of trees and help the trees absorb water and minerals; in return, the trees provide the mushrooms with nutrients. Milkcaps can even transfer nutrients from one tree to another, so that older Douglas Firs help younger ones grow. 

 observation by caladri

The red-bleeding milk cap's partnerships with trees are very easy to study. In several studies of mature forests on Vancouver island, about a quarter of all trees were symbiotic with this species. Scientists can figure out underground fungal threads belong to Red-Bleeding Milk Caps and which trees they have colonized even without a DNA test - the fungal threads and the tree roots they colonize bleed red, too!

 observation by caladri

Happy belated Halloween from Lactarius rubrilacteus, the spooky mushroom that makes the whole forest bleed!

Posted on December 6, 2020 09:47 PM by corvi