Because they prefer dark, moist conditions, termites make these earth-colored tubes primarily as protected runways from the earth to the wood they feed on. They also may serve as swarming exits for winged termites. Wood attacked by termites has channels or passages coated with an earth-like material. Where the wood has been infested for some time, it may be largely hollowed out with passages and may look rotten. When such wood is probed with a screwdriver, many worker termites spill out.
Most infestations occur in basements and in the structural timbers just above cellar walls.
Wooden posts, steps, door frames and trim embedded in an earthen or concrete floor are especially susceptible. Termites particularly favor areas around furnaces, chimneys and hot water heaters and pipes that provide warmth during winter. Many houses in Pennsylvania are unlikely to ever have termites because they are located in low-risk areas or are constructed to resist infestations. Remove all wooden debris from around the building. Replace wooden posts, steps, trellises and other structures that contact the soil with noncellulose materials or pressure-treated lumber.