Treating Termite Infestations

- Use soil treatment and baits -

Summary: Most termite treatments should be done by a pest control company that has access to materials and experience beyond that of the average homeowner. Some do it yourself termite baits are now available, however.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

Soil treatments for termites

Subterranean termites start their colonies in the soil then extend it into structures where damage occurs. Because the "root" of the colony is always in the soil, termite treatments usually involve applying insecticide to the soil.

In the past, highly toxic and persistent insecticides, like chlordane and heptachlor, were applied to the soil during construction to prevent termites from building colonies around the structure. Nowadays less toxic and environmentally damaging materials like bifenthrin , fipronil, imidacloprid, permethrin and cypermethrin are used. These "pre-construction" treatments create a toxic barrier that prevent termites in the soil from moving into the structure and also stop colonies from getting started (see How Termite Biology Affects Treatment Options).

house foundation drawing

Subterranean termite entry points. Original drawing from Wood-Inhabiting Insects in Houses by Harry B. Moore, 1979. USDA, Forest Service and HUD. Click the image for an enlarged view of termite entry points.

Soil treatments can also be applied after construction ("post-construction") by injecting insecticide into the soil or by digging a trench around structures and treating the soil directly. Both pre- and post-construction treatments should be performed by a pest control firm because they require special equipment and experience. See our suggestions for Selecting Pest Control Services.

Spot treatments

If you need to spot treat an area, for example an individual colony and mud tubes, you can use Termidor Insecticide. Termidor is available in relatively small package size and can be applied with a garden sprayer.

Baits for subterranean termites

While pre- and post-construction insecticide treatments are probably best left to a pro, you can control termites yourself with termite baits if you are willing to spend the time and effort. Termite baits are relatively new in the battle with these wood-destroying insects. Poison baits are made of a cellulose material that has been laced with an insect growth regulator or insecticide. Termite bait stations are generally placed at or below ground level where foraging worker termites find them, feed on the bait and take the poison back to the colony (see Do Termite Baits Really Work As a DIY Project?).

Other termite species

There are numerous species of "subterranean" termites that differ by region. You should consult with local experts to find out the best way to protect structures in your area. However, in general, structures should be protected from subterranean termites by a combination of soil treatment (pre- or post-construction) and baiting. In areas with Formosan subterranean termites (Gulf Coast, US, Hawaii, northern Australia) you should be especially diligent because of this termite's potential for rapid and extensive damage.

Drywood termites occur mostly in arid and coastal regions, for example most of California in the US, where they to can do significant damage. This termite may built colonies above ground, entirely concealed in the structure and unlike their subterranean cousins, they do not need contact with soil. Often, damage to cabinets and furniture can be more significant than damage to structural timbers (see What are Drywood Termites?).

Dampwood termites also nest above ground but require wood that is continuously wet. Generally when the affected wood is made dry, such as by repair of a collapsed foundation, the termites disappear. However, structures in especially damp climates may be attacked directly.

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