• Proposed
  • Under Assessment
  • Preliminary Assessed
  • LCAssessed
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Inonotus obliquus (Ach. ex Pers.) Pilát

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Scientific name
Inonotus obliquus
(Ach. ex Pers.) Pilát
Common names
błyskoporek podkorowy (włóknouszek ukośny)
Must pässik
polypore incrusté
Melnā spulgpiepe
IUCN Specialist Group
Mushroom, Bracket and Puffball
Assessment status
Preliminary Category
Proposed by
Else Vellinga
Else Vellinga
Dan Richman
Comments etc.
Irmgard Krisai-Greilhuber, Nicolas Schwab, Irja Saar, Inita Daniele, Izabela L. Kalucka, Tatyana Svetasheva, Anders Dahlberg

Assessment Notes



Chaga (Inonotus obliquus) is a parasitic fungus and widely distributed in the circumboreal region of the Northern Hemisphere. It forms sterile black cancers mainly on Birch (Betula spp), but also on other deciduous trees. When the host tree dies, which may take 50-80 years, it will form fruitbodies that develop under the bark of the tree and are hardly visible. The sterile cancers are harvested because of their (presumed) health benefits. Overharvesting, especially near settlements and along roads into the northern birch forests can be local and form a regional threat. The state of Alaska (USA) limits harvesting of all conks (excl. Laricifomes officinalis) on public land to 10,000 lbs per year per person. Poaching on private lands is becoming a problem in some parts of the USA. However, the species is common and widespread in Eurasia and there is no evidence of decline. It can be locally abundant where suitable habitat exists. Therefore, it is assessed as Least Concern (LC).


Taxonomic notes

Why suggested for a Global Red List Assessment?

Geographic range

Circumboreal (Gilbertson & Ryvarden 1986), known from Canada, USA, United Kingdom, Norway, the Netherlands, Belgium, Germany, Austria, Italy, Denmark, Czech Republic, Estonia, Finland, Sweden, Poland, Russian Federation.

Population and Trends

It is a widely distributed and common species. In Russia 1–20% of the trees in a natural birch stand show signs of infection (Kuzmichev et al., 2001).

Population Trend: Uncertain

Habitat and Ecology

Inonotus obliquus is a parasite and necrotroph, mainly on Betula species, but also on Alnus (e.g., in norther Europe). It forms sterile tissue in the tree (the conk, also called chaga), and after the tree dies, mature sexual fruitbodies which develop under the bark. A chaga only produces sexual fruitbodies after the death of the host tree.  Harvesting full chaga conks eliminates the ability for chaga to reproduce. Its spores are beetle and wind dispersed.

Boreal ForestSubarctic Forest


The most significant threat to Chaga is from commercial foragers and loggers. In Canada, loggers are harvesting birch wood which may have chaga growing on them. In Alaska, every non-timber forest product harvester is legally permitted to harvest 10,000 Lbs of chaga and other conks (excl. Laricifomes officinalis) per year, with no regard to the sustainability of the conk or the survival of its host tree. Commercial foragers are already exploiting this lax quota. Alaska has not set any guidelines for sustainable harvesting of the conk, despite the fact that improper harvesting techniques can cause damage to the tree and eliminate any potential future growth of chaga. It’s traditionally used in Russia for making tea and for medicinal purposes In Russia, but is a common and widely distributed species, as is its host Betula, and there is no indications of decline from Russia.

Intentional use (species being assessed is the target)Logging & wood harvesting

Conservation Actions

Some botanists and health writers, such as Arthur Haines and David Wolfe have produced educational videos and books informing individuals on how to conserve their chaga usage.

Education & awareness

Research needed

It is unknown if efforts are being made to track the population of chaga while commercial chaga foragers and sales of chaga have grown significantly over the past decade. A 2004 Assessment of sustainable commercial harvesting in Khabarovsk and Primorsky Krais, Russia concluded that commercial harvesting of chaga in no way endangered this abundant conk, but that the species could be locally over-harvested. Without efforts at enhancing production, the harvest might become economically unsustainable, as collectors need to travel further from towns and cities to find specimens. However, further research is likely needed as the demand for chaga has grown significantly since 2004, when the last assessment was undertaken. Forest ecologists have a vested interest in understanding the long-term ecological role of Chaga, as the chopping off of wild Chaga may accelerate beetle and other blights with untold downstream impact. This onslaught for short-term profit may inflict long-term ecological damage, though more research is needed to fully understand the scope and long-term impacts.

Population trendsHarvest level trendsHabitat trends

Use and Trade

The sterile cancers are harvested because of their (presumed) health benefits to make tea and other health products. Chaga is also being studied extensively for its anti-cancer, anti-fungal, anti-diabetes, and anti-bacterial properties, and even in HIV research.

Medicine - human & veterinary


Alaska Non-Timber Forest Products Harvest Manual for Commercial Harvest on State-Owned Lands, State of Alaska Department of Natural Resources Division of Mining, Land and Water, April 2, 2008.

Bowser, M., 2015. The chaga poachers. Refuge notebook 17 (21): 41–42.

Gilbertson, R.L. & Ryvarden, L., 1986. North American Polypores I. Fungiflora Oslo, Norway.

Kuźmichev, E.P., Sokolova E.S. & Kulikova E.G., 2001. Common fungal diseases of Russian Forests. USDA, Forest Service, Northeastern Research Station General Technical Report NE-279/

Pilz, D. 2004. Chaga and Other Fungal Resources – Assessment of Sustainable Commercial Harvesting in Khabarovsk and Primorsky Krais, Russia. PilzWald Forestry Applications of Mycology (assessment report)

Pilz, D. 2012. Chaga harvesting in the land of the Siberian tiger. FUNGI 5 (3): 13–17.

Thomas, P.W., Eikhateeb, W.A., Daba, G.M., 2020. Chaga (Inonotus olibquus): a medical marvel but a conservation dilemma?  Sydowia 72: 123–130. DOI 10.12905/0380.sydowia72-2020-0123

Country occurrence

Regional Population and Trends

Country Trend Redlisted