Fungi are lower vegetable organisms without chlorophyll that feed on already elaborated organic material. This material may be the remains of organisms which had at one time been alive (in this case the Fungi are the so called Saprophytes) or an integral part of living organisms (in this case the Fungi are Parasites). The importance of fungi in the wood sector is particularly relevant because of the destruction and disruption they cause in the wood.

Wood cavity fungi 
In order for these fungi to develop the wood must have a humidity level of over 20%.

  • Basidiomycetes cavity fungi: are fungi which when they attack the cellulose cause a loss in size of the wood, together with the formation of prism or cube shaped soft cracks, so soft they can be squashed with the fingers. The development area of the fungi becomes brown, thus the name brown or destructive cavities.
    Should the attack by basidiomycetes not be limited only to the cellulose but also attack the lignin, the colour of the wood becomes lighter than the healthy material and is reduced to a whitish fibrous mass (white or corrosive cavities). 
     
  • Deuteromycetes soft cavity fungi: fungi that cause a type of cavity characterised by softening of the surface of the wood, although it can also cause deep cavities. These fungi need a higher humidity level than the one required for basidiomycetes. They are particularly important for wood that is in contact with the ground or water.

Figure 1.1: spreading of the "dark spot" fungus called "soft cavities" which will gradually destroy the structure of the wood making it similar to a brittle sponge.

 

 

 

 

Colouring fungi
They cause the bluing and mildew on installed wood. These fungi may cause concern only from the point of view of aesthetics, spoiling in some cases decorative panelling.

  • Bluing fungi: they cause permanent colouring from blue to black and at various depths, above all in the alburnum of certain wood. Attacks by these fungi do not impair the mechanical properties of the wood, but may increase the level of permeability.

Figure 1.2: action of blue fungus that during its development succeeds in breaking through the film of coating and reach the surface.

 

 

 

 

  • Mildews: fungi which appear as spots in various colours on the surface of damp wood and which can appear only when the humidity on the surface of the wood is over 20%. This condition appears when there is high relative humidity or condensation from steam. The attack by mildew does not have an important influence on the mechanical properties of the wood but which gives the wood an unwanted and unacceptable appearance. These fungi are not specific to wood and may appear on any material where humidity is high.