The ability to identify wood decay fungi is an important skill for an arborist. Knowing which fungus is colonizing a tree can be used to better assess the type, amount, and position of decay in the tree, and its subsequent effects on wood strength. Distinguishing species of fungi that colonize sapwood, heartwood, or roots can provide information to improve the quality of the risk assessment. For example, sapwood decaying agents colonize areas of the trunk that have been wounded or injured by other agents, but do not usually penetrate deeply into the wood. Climbing a sapwood-degraded tree can be very dangerous, as the outer wood is weakened and can give way.
Glaeser, Jessie A. 2012. Online resources for the identification of North American wood decay fungi. Arborist News. December: 55-56.