Pressure-Treated Wood, Mulch and Termites

Pressure-Treated Wood Facts

• The use of chemicals to preserve wood and to protect it from decay due to fungus and wood-destroying insects, such as termites, has a long history. Most of the pressure-treated wood sold in the United States contained copper, chromium and arsenic. In 2003, the Environmental Protection Agency (EPA) announced that these elements, and especially arsenic, presented a high enough level of toxins and carcinogens to be discontinued. The EPA then provided a list of chemicals that they deemed safe for commercial distribution, including quaternary ammonium compound, borates and copper azole.

Mulch Facts

• Mulch in the garden is a useful technique that helps keep weeds to a minimum and also retains moisture in the soil. However, there are concerns about whether termites are attracted to mulch or whether termite infestations are aided by laying mulch in the garden. According to the University of Florida Agriculture Extension Department in 2007, mulch in gardens presents more of a risk for aiding current termite infestations than for the introduction of termites through infested products.

How Termites Infest From the Outside

• One way in which termite infestations affect a home from the outside is when drywood termite swarmers -- winged reproductives -- land near a home and look for an appropriate place to burrow in and start a new colony. This place would be anything made of wood or paper, since the insects need the cellulose found in these materials for sustenance. That means that structural elements of a home siding, eaves, window and door frames, as well as exterior elements such as decks, patios and mulch in gardens, are targets for new termite infestations.

Subterranean Termites

• Perhaps the most difficult types of termite infestations to guard against from the outside are by subterranean termites, because they nest in the soil. They gain access to a home much like ants do, through cracks in a slab or by using conduits such as plumbing and electrical lines and support piers in a raised foundation. Unlike ants, however, they can build a colony near the home using wood that is close by, such as attached decking, patios or mulch in gardens. Mulch is especially beneficial, because it also provides the moisture all termites need to survive.

What Can Be Done?

• Certain types of wood mulch are believed to be useful against termite infestations because of their hardness or a natural resistance to insects, including cedar and redwood. However, this resistance doesn't last forever, and eventually termites will be able to infest these mulches. Pressure-treated wood will also lose its resistance to infestation over time. The only sure way to use these products is to replace or refresh the mulch every few years and to use wood preservatives on decks and patios on a regular basis -- once a year is best.