Under proper conditions, wood will give centuries of service. However, if conditions exist that permit the development of wood-degrading organisms, protection must be provided during processing, merchandising, and use.
The principal organisms that can degrade wood are fungi, insects, bacteria, and marine borers.
Molds, most sapwood stains, and decay are caused by fungi, which are microscopic, thread-like microorganisms that must have organic material to live. For some of them, wood offers the required food supply. The growth of fungi depends on suitably mild temperatures, moisture, and air (oxygen). Chemical stains, although they are not caused by organisms, are mentioned in this chapter because they resemble stains caused by fungi.
Insects also may damage wood, and in many situations must be considered in protective measures. Termites are the major insect enemy of wood, but on a national scale, they are a less serious threat than fungi.
Bacteria in wood ordinarily are of little consequence, but some may make the wood excessively absorptive. In addition, some may cause strength losses over long periods of exposure, particularly in forest soils.
Marine borers are a fourth general type of wood-degrading organism. They can attack susceptible wood rapidly in salt water harbors where they are the principal cause of damage to piles and other wood marine structures.
Wood degradation by organisms has been studied extensively, and many preventive measures are well known and widely practiced. By taking ordinary precautions with the finished product, the user can contribute substantially to ensuring a long service life.