In order to prevent subterranean termites from establishing infestations within structures, new homes in California are typically built with pressure-treated lumber. However, it is not standard practice to construct homes entirely out of pressure-treated lumber components; instead, the substructural sills located close to the ground surface are usually the only wood sources within California homes that are pressure-treated. This is an understandable practice, as subterranean termites dwell solely within soil where the sills are the first lumber components that subterranean termites make contact with. Ideally, upon making contact with pressure-treated sills, subterranean termite workers would be deterred from making further attempts to establish an infestation. Unfortunately, it is not uncommon for subterranean termites to bypass repellent pressure-treated sills in order to establish infestations within untreated lumber components located higher up within homes.

Pressure-treated wood often repels subterranean termite workers, but the few that do consume pressure-treated wood quickly die from the arsenic-based chemicals that coat sills. It is not difficult for subterranean termite workers to create “shelter tubes” that go around sills where they make direct contact with other lumber components near the ground surface, such as studs and joists. In order to address this shortcoming, many homeowners and lawmakers are in favor of enacting state laws that require all of a home’s structural lumber components to be pressure-treated to resist termite attacks. Surprisingly, constructing homes entirely out of pressure-treated structural wood only costs 2% more than construction projects that use only non-treated lumber. Furthermore, while pressure treated lumber sills offer homes some degree of protection from subterranean termite attacks, such a limited treatment is completely ineffective at preventing infestations of drywood termite pests, which are almost as common as subterranean termites in southern California. For example, the most common drywood termite pest in Ventura County, the western drywood termite (I. minor), initiates structural infestations as winged swarmers (alates), which means they, unlike subterranean termite workers, can establish new colonies in just about any exterior or interior structural wood component of a home. In fact, these termites are particularly resistant to secondary compounds on structural wood, and studies have shown that they avoid infesting untreated redwood and cedar wood, as they seem to have a distaste for these species.

Does your home contain pressure-treated lumber components?