Wood-Destroying Pests Can be Picky

Editor’s Note: This article was reprinted from Techletter with permission of Pinto & Associates, Inc.

Wood-destroying pests (insects and fungi) can be grouped into those that damage (1) standing trees or newly felled logs, (2) sawn timber and wood products during seasoning or storage, and (3) wood in use. Pest control technicians and their customers are primarily concerned with pests that attack seasoned wood in use. But keep in mind that any infestation may have started much earlier, before that wood was actually in use.

The chances of attack by some insects is related to how the wood was handled during milling and storage. Other insects attack only stressed trees and in the process of lumber production end up "built in" to structures. These insects will typically complete development in the timbers and emerge, but most will not reinfest because conditions, particularly wood moisture, are no longer suitable.

Three things are necessary when pests infest wood: a source from which the infestation spreads, susceptible wood, and suitable conditions of temperature and humidity. Some insects can tolerate wide ranges of temperature and humidity and can be found infesting wood in a wide range of sites. Other insects are very limited in their tolerance to physical conditions and are, therefore, limited in the locations and types of wood they can infest.

Wood-destroying pests may also be grouped as to whether they attack hardwoods or softwoods, or attack heartwood or sapwood. A few pests attack more than one of these groups. Fungal decay in wood often makes it more susceptible to infestation by insects, but may also repel some insects.