It looks like streaks of rust colored paint then becomes thicker as the stroma develops and perithecial bumps appear.
Stroma flat to bumpy with perithecia obscure or conspicuous. Surface rusty to dark brick colored, possibly more yellow-brown at times; inner stroma dark brown. If stroma margin extends beyond the perithecia it may be more brightly colored. KOH-extractable pigments are orange to rust colored.
The conidial state is reddish-gray to brown, powdery, below the bark, and precedes the appearance of the perithecial stroma.
Hypoxylon fragiforme is reddish but appears as separate round balls. For other similar species see the literature and links below.
Typically on decorticated wood (without bark).
A mild pathogen on most hosts associated with decay of timber. Found on hardwood trunks and branches of many species including maple, ash, elm, basswood, willow. Spread by both conidia and ascospores.
Persistent stroma can be found year round.
Widespread in northern temperate areas, Europe, North America.
Chicago Region status
Twelve historic collections, 1902 - 1909 (Harper), 1941 (Graham) and seventeen recent specimens, 1996 - 2019 (Leacock, Gaswick, et al.). Drew Minnis made the first recent identification in 2008 at a Smith Foray at Indiana Dunes. Then in 2019, Leacock examined recent unknown red crusts and identified sixteen more research collections.
Taxon Details and Links
Summa vegetabilium Scandinaviae 2: 384 (1849)