Irpex lacteus is a common crust fungus distributed throughout temperate areas of the world.

Irpex lacteus is considered a polypore, but depending on growth conditions it can also produce a hydnoid hymenophore.

[1] Irpex lacteus is a white-rot fungus that inhabits mainly angiosperm branches and trunks.

[2] It is one of the most common wood-rotting fungi for instance in urban North America.

[4] The fungus was first described in 1818 by Elias Magnus Fries, who called it Sistotrema lacteum.