page_title: Fomitopsis betulina
section_title: Range and ecology
hierarchical_section_title: Fomitopsis betulina / Range and ecology
caption_attribution_description: Variation in size and colour of the Piptoporus betulinus (Birch Polypore or Razorstrop Fungus or Birch Bracket, D= Birchenporling, F= Polypore du bouleau, NL= Berkenzwam), white spores, causes brownrot at Schaarsbergen forest
context_page_description: Fomitopsis betulina, commonly known as the birch polypore, birch bracket, or razor strop, is a common bracket fungus and, as the name suggests, grows almost exclusively on birch trees. The brackets burst out from the bark of the tree, and these fruit bodies can last for more than a year.
context_section_description: Fomitopsis betulinus is one of the most common species of brown rot fungi. The geographic distribution of F. betulina appears to be restricted to the Northern Hemisphere, including Northern America, Europe, and Asia. It is only found on birch trees, including Betula pendula, B. pubescens, B. papyrifera, and B. obscura. There is some doubt about the ability of isolates from the European continent, North America and the British Isles to interbreed.
  It is a necrotrophic parasite on weakened birches, and will cause brown rot and eventually death, being one of the most common fungi visible on dead birches. It is likely that the birch bracket fungus becomes established in small wounds and broken branches and may lie dormant for years, compartmentalised into a small area by the tree's own defence mechanisms, until something occurs to weaken the tree. Fire, drought and suppression by other trees are common causes of such stress.
  In most infections there is only one fungal individual present, but occasionally several individuals may be isolated from a single tree, and in these cases it is possible that the birch bracket fungus entered after something else killed the tree. These fungal "individuals" can sometimes be seen if a slice of brown-rotted birch wood is incubated in a plastic bag for several days. This allows the white mycelium of the fungus to grow out of the surface of the wood. If more than one individual dikaryon is present, lines of intraspecific antagonism form as the two individual mycelia interact and repel each other.
  The fungus can harbor a large number of species of insects that depend on it for food and as breeding sites. In a large-scale study of over 2600 fruit bodies collected in eastern Canada, 257 species of arthropods, including 172 insects and 59 mites, were found. The fungus is eaten by the caterpillars of the fungus moth Nemaxera betulinella. Old fruit bodies that have survived the winter are often colonized by the white to pale yellow fungus Hypocrea pulmonata.
caption: Variations in size, shape, and surface colour of birch bracket
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