Armillaria solidipes (formerly
Armillaria ostoyae) is a species of fungus in the
Physalacriaceae family. It is the most common variant in the western U.S., of the group of
species that all used to share the name
Armillaria mellea.
Armillaria solidipes is quite common on both
hardwood and
conifer wood in forests west of the
Cascade crest. The
mycelium attacks the sapwood and is able to travel great distances under the bark or between trees in the form of black
rhizomorphs ("shoestrings").