They also may serve as swarming exits for winged termites. Look for these tubes on cellar walls, wooden posts, exterior masonry and trim around doors and windows. 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. Replace wooden posts, steps, trellises and other structures that contact the soil with noncellulose materials or pressure-treated lumber. Replace badly damaged timbers with sound materials. Where possible, don't allow wood within 18 inches of the soil.