Termites rely on cellulose in plant matter as their sole source of nutrition, and this is a good thing from an ecological perspective. Trees and plants would cease to grow if termites were not around to recycle the dead wood that collects on the surface of ground soil. Unfortunately, of the more than 3,000 documented termite species worldwide, a very small minority frequently feed on structural wood in homes and buildings, which results in more than 40 billion dollars in property damage worldwide every year. Although the US is home to a relatively small number of termite species that are known to infest woodwork, the annual cost of termite-related property damage in the country exceeds five billion dollars.
Several species from all three groups of termites, subterranean, drywood and dampwood, infest timber-framed structures in the US, but only one, Reticulitermes flavipes, can be found in Massachusetts. R. flavipes is more commonly known as the “eastern subterranean termite,” and it’s the most economically costly wood-destroying insect pest in the US. However, subterranean termites cannot indiscriminately infest any source of structural wood that they encounter, as their high moisture requirements make dry woods unsuitable for infestation and consumption.
Studies have shown that workers from subterranean termite colonies do not forage in the direction of wood; instead, subterranean termite workers follow moisture gradients in soil. The relative humidity within their underground foraging galleries is almost always at 100 percent, which minimizes the rate at which their bodily fluids evaporate through their relatively thin cuticle. When workers approach the ground surface, the increasingly dry air accelerates the rate at which they lose water, and if subterranean termites are exposed to the outside air, they rapidly dry up and die.
According to the Environmental Protection Agency, a moisture meter reading 28 to 30 percent means that structural wood is just beginning to become susceptible to subterranean termite infestations. Substructural wood components within a crawl space are the first to be attacked by subterranean termites and they are also the moistest wood components within a home. Keeping a dehumidifier set at 55 to 60 percent relative humidity within crawl spaces will help make structural wood less appetizing to subterranean termites.
Have you ever measured wood moisture content or relative humidity within your crawl space?