Birch Polypore

The birch polypore (Fomitopsis betulina, formerly Piptoporus betulinus), also called birch bracket or razor strop fungus, is a bracket fungus of the family Fomitopsidaceae in the order Polyporales, with a smooth greyish-brown top surface and a creamy white underside covered in hundreds of pores; its fruiting body is rubbery when fresh and grows corky with age, and infected wood often smells distinctly of green apples. It is restricted to the Northern Hemisphere, across North America, Europe, and Asia, and grows almost exclusively on birch trees, including silver birch and paper birch. It is a necrotrophic parasite of weakened birches, causing brown rot that can eventually kill the tree, and is among the most common brown rot fungi; its conservation status is listed as Secure by NatureServe.