Wood Wise Words from the World of Wood

Under proper conditions, wood will give centuries of service. However, under conditions that permit the development of wood-degrading organisms, protection must be provided during processing, merchandising, and use. Organisms that can degrade wood are typically fungi, insects, bacteria, and marine borers.

This Wood Wise series is dedicated specifically to decay, the decomposition of wood substances by fungi.

Advanced (Typical) Decay: The older stage of decay in which the destruction is readily recognized because the wood has become punky, soft and spongy, stringy, ringshaked, pitted, or crumbly. Decided discoloration or bleaching of the rotted wood is often apparent.

Brown Rot: In wood, any decay in which the attack concentrates on the cellulose and associated carbohydrates rather than on the lignin, producing a light to dark brown friable residue—hence loosely termed “dry rot.” An advanced stage where the wood splits along rectangular planes, in shrinking, is termed “cubical rot.”

Dry Rot: A term loosely applied to any dry, crumbly rot but especially to that which, when in an advanced stage, permits the wood to be crushed easily to a dry powder. The term is actually a misnomer for any decay, since all fungi require considerable moisture for growth.

Incipient Decay: The early stage of decay that has not proceeded far enough to soften or otherwise perceptibly impair the hardness of the wood. It is usually accompanied by a slight discoloration or bleaching of the wood.

Heart Rot: Any rot characteristically confined to the heartwood. It generally originates in the living tree.

Pocket Rot: Advanced decay that appears in the form of a hole or pocket, usually surrounded by apparently sound wood.

Soft Rot: A special type of decay developing under very wet conditions (as in cooling towers and boat timbers) in the outer wood layers, caused by cellulose?destroying microfungi that attack the secondary cell walls and not the intercellular layer.

White?Rot: In wood, any decay or rot attacking both the cellulose and the lignin, producing a generally whitish residue that may be spongy or stringy rot, or occur as pocket rot.

From the Wood Handbook: Wood as an Engineering Material, FPL–GTR–190.