Wood-decay Fungus - Brown Rot

Brown Rot

Brown-rot fungi break down hemicellulose and cellulose. Cellulose is broken down by hydrogen peroxide (H₂O₂) that is produced during the breakdown of hemicellulose. Because hydrogen peroxide is a small molecule, it can diffuse rapidly through the wood, leading to a decay that is not confined to the direct surroundings of the fungal hyphae. As a result of this type of decay, the wood shrinks, shows a brown discoloration, and cracks into roughly cubical pieces; hence the name brown rot or cubical brown rot.

Brown rot in a dry crumbly condition is sometimes incorrectly referred to as dry rot in general. The term brown rot replaced the general use of the term dry rot, as wood must be damp to decay, although it may become dry later. Dry rot is actually a generic name for certain species of brown-rot fungus that have water-conducting strands capable of carrying water (usually from soil) that enable it to decay normally dry wood. It is also called true dry rot.

Brown-rot fungi of particular economic importance include Serpula lacrymans (true dry rot), Fibroporia vaillantii (mine fungus), and Coniophora puteana (cellar fungus), which may attack timber in buildings. Other brown-rot fungi include the sulfur shelf, Phaeolus schweinitzii, and Fomitopsis pinicola.