Wood and wood-based materials can be ruined by wood-destroying fungi. In and on the wood, the fungi form thread-like networks of hypha, referred to in their entirety as mycelia.
As a rule, such fungi only flourish on wood or wood-based materials with a high moisture content. The fungi normally need a temperature range of between +3°C and +40°C and a minimum moisture level of over 15% to develop properly.
Wood-destroying fungi are divided into three main groups; brown rot, white rot and soft rot types.
What are brown rot fungi?
Brown rot fungi mainly degrade the wood’s carbohydrates, i.e. the cellulose and hemicelluloses. The infested wood turns brown in colour because the dark brown lignin in the wood remains as a residue.
The wood loses density, volume and strength, shrinks noticeably when it dries and shows longitudinal and lateral cracks, which give it a characteristic “checkerboard” appearance (so-called “cubic” rot). In the final stage, the wood can be crumbled between the fingers to a brown powder.
Brown rot fungi are mainly found in coniferous wood, though some can be found on hardwood or on both hardwood and softwood. They occur in both living and weakened trees, as well as in the heart and sapwood of processed timbers.
The brown rot fungi include dry rot, wet rot, antrodia sinuosa and bracket fungi.
What are white rot fungi?
White rot fungi degrade both the lignin and the cellulose in the wood cell walls. While this is going on, the wood structure remains largely unchanged for quite a long time, unlike brown rot infestation. The wood loses density and strength and turns brighter in colour. It often maintains its fibrous structure, even into the final stages, with cube-like crumbling scarcely occurring.
On wood infested with white rot, dark coloured lines can occasionally be seen that separate the areas affected from areas of healthy wood or wood infested with other fungus species. White rot mainly tends to attack coniferous wood.
White rot fungi include wet rot, root rot, the Turkey tail, the Tinder or Hoof fungus and also the asterostroma cervicolor fungi.
What are soft rot fungi?
Soft rot fungi degrade the carbohydrates in the wood cell wall. They mainly occur in permanently moist wood that is constantly exposed to water or damp, moist soil.
Soft rot fungi attack the wood from the surface, turning the outer layers a dark, greyish-black colour. The infested areas are soft and greasy and crack across the grain when they dry. This discoloured, infested surface layer distinguishes itself clearly from the healthy wood lying beneath it.
Soft rot can attack all coniferous and hardwoods. They belong to the acomycetes or deuteromycetes (Fungi imperfecti) groups and do not form a large fruiting body. Other typical white rot fungi belong to the chaetomium, phialophora und humicola species.