Dry rot

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Dry rot is an almost oxymoronic term given to the decay of a substance without the presence of water. The term has been applied to the decay of timber in timbers by specific fungus, the decay of crop plants by fungi and the deterioration of rubber. In addition, the term can be used as a metaphor for grave underlying problems within a large organization (such as political corruption in government or low morale in the armed forces) that show no symptoms until a sudden, catastrophic failure.

The term is most commonly used in reference to the decay of building timbers. It refers to damage inflicted by either: Serpula lacrymans (formerly Merulius lacrymans) predominantly in the United Kingdom and northern Europe; and/or Meruliporia incrassata (which has a number of synonyms, including Poria incrassata) in North America. These are different species (and indeed belong to different families of fungi) that share the same false moniker. Both species of fungus use the Brown rot decay mechanism to remove cellulose and hemicellulose from the timber eventually causing instability and collapse in houses, ships' hulls, and other wooden structures.

When applied to these fungi, the term is a misleading misnomer as both species require an elevated moisture content to initiate an attack on timber (28-30%). Once established, the fungi can remain active in timber with a moisture content over 20% - in the same way as other timber decay fungi (termed: wet rots) using the brown rot decay mechanism.