Dealing with Wood-Boring Insects

Wood-eating insects fall into two groups—subterranean (those that eat wood but nest underground) and nonsubterranean (those that live in the wood itself). Watch for subterranean insects in early spring and fall. This is when the reproductive members of termite colonies sprout wings, take off on mating flights, discard the wings, and establish nesting places. If you find a pile of wings, suspect a colony nearby.

Nonsubterranean wood-boring insects, including powder-post beetles and carpenter ants, as well as several termite species, remain above ground. Sometimes you can spot their entrance holes in the wood’s surface; a pile of sawdust pellets is another telltale sign. If you suspect termites, call a licensed pest exterminator. Don’t panic—although these pests can demolish a house, it would take years to do so.

Exterminators surround the house with what amounts to an underground moat of insecticide, usually by injecting chemicals into the soil with special equipment. Isolated from the earth, worker termites in the house soon die of thirst; the remainder of the colony starves or moves on. Nonsubterranean termites confine their activities to limited areas, such as the inside of a porch column, a window, or a door frame. If the wood has not been weakened structurally, the extermination process will consist of boring holes into the wood and injecting a liquid or powdered chemical. If the damage is more extensive, the wood member must be cut away and replaced with new treated lumber.

Termites. Termites resemble ants but have cylindrical bodies and are light gray in color. During the mating season, workers have two pairs of equal-sized wings; otherwise they are wingless. Most termites live in the ground outside the house and make daily forays into the house to retrieve wood fibers.

Termite damage. Subterranean termites form tunnels in the direction of the wood grain, sometimes leaving nothing but a shell. By the time the damage is visible, the board is typically too far gone to save.

Carpenter ants. Winged carpenter ants have a very thin waist called a pedicel, and the back pair of wings is shorter than the front. Carpenter ants make their homes in moist wood. If you take steps to keep out moisture, they will die off.

Carpenter ant damage. Nonsubterranean insects burrow across the grain. Occasionally their tunnels break through the surface. This type of damage often becomes evident in time to save the board.

How they get in. Most termites live in the forest, where they have an abundant supply of food in the form of dead and fallen trees. Unfortunately they don’t distinguish between wood in its natural state and wood that has been through a sawmill. To discourage termites from picnicking in your home, clear away any firewood or construction debris near your house. Because they can gain access through even tiny holes, you will probably not be able to fence them out. Call in an exterminator if they have already invaded your home.

Apply insecticide in a crawlspace. Many homes in termite-infested areas are built on crawlspace foundations. Termiticide should be applied around the bases of all rigid structures that are between the soil and the sill or floor framing. These structures include masonry walls, masonry piers, and plumbing pipes. As a second line of defense, foundation walls and piers should be capped with sheetmetal termite shields. Know the effective life of your shields and replace them before your house is reinfested.

Treating a basement. Professionals treat full-basement foundations as if they were boats floating in a sea of termites. The soil outside the wall is treated all the way to the footing, and termiticide is applied to the entire soil surface before the basement floor slab is poured. If the foundation wall consists of hollow masonry blocks, the wall is capped with solid concrete and a sheetmetal shield. If termites are found after the home is built, holes are typically drilled and filled with termiticide all around the foundation.

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