Homes in the South and Southwest are vulnerable to attack by dry-wood termites as well as subterranean termites. Dry-wood termites cannot live outdoors in northern climates and have not established themselves in those areas. Isolated cases of dry-wood termite infestation have been found in homes located as far north as New York and Ohio, but those are rare.
Dry-wood termites are so called because they build their nest in perfectly good wood that is not decayed and not in contact with the ground. In fact, in many cases they establish a colony in the wood-framing members of the attic. As with subterranean termites, reproductive dry-wood termites swarm from the nest periodically in an attempt to establish a new colony. The swarming termites often do not fly more than a few feet before settling down. However, if aided by air currents, they can fly more than a mile. Once paired, the king and queen seek cracks or checks in nearby wood, whether a roof or lumber pile, and set up housekeeping. In homes, dry-wood termites can be found in rafters, studs, joists, sheathing, floorboards, window frames, door frames, and exterior trim.
Once a colony is established, it feeds on the wood around the nest. Dry-wood termites are general feeders and eat spring- and sum-mer-grown wood. The galleries thus formed will cut across the grain. The cavities contain pellets of partially digested wood. These pellets are tiny, seedlike, and usually straw-colored. On occasion, some of the pellets are pushed through openings in the wood surface. If there is not much accumulation, the pellets can easily be overlooked. They are, however, often the first sign of infestation.
The maximum population of a fully established dry-wood termite colony is estimated to be about 3,000. This is considerably less than the typical number of subterranean termites in an established colony, which is estimated to be between 60,000 and 250,000. Consequently, it takes a longer period of time for serious damage to occur with dry-wood termites than with subterranean termites.
Control Since dry-wood termites do not nest in the ground, they must be chemically treated at the source of infestation. This is usually done by injecting insecticide into the galleries, a procedure that should be performed by a professional. To reach the galleries, holes are drilled in the infested wood members. The insecticide will be a liquid or a dust. When the wood is dry, dusting can be effective as far as 15 feet from the point of application. However, when the wood is wet, dusting usually is not effective because the dust tends to cake in the moist galleries. If dry-wood infestation is found in a fence or pole on the property, those wood members should be treated since the termites represent a potential source of infestation for the house.
For severe infestation, treatment is usually by fumigation. The entire house, including the roof, is wrapped with a plastic covering. After all the openings are sealed, a poisonous fumigant is introduced. The house should remain under fumigation for at least forty-eight hours. Since the insecticide is poisonous to humans, fumigation should be undertaken only by experienced fumigators.
Inspection Since dry-wood termites do not leave their nest in search of food, there are no telltale signs of infestation such as shelter tubes. They can be detected, however, by their pellets, which tend to accumulate in a small pile after being pushed from the wood by the termites or falling through a crack in the infested wood. An infestation in the house can also be detected by the presence of a swarm if you happen to be in the room during an occurrence. Since dry-wood termites can attack wood located anywhere in the house, from the attic to the crawl space, all the exposed wood should be checked for signs of infestation. The wood should be gently probed, so as not to break the surface. Infested wood has hollow sections and if heavily probed, can break open, spilling the seedlike pellets. Dry-wood termites often consume wood up to the paint itself, forming what appears to be a paint blister. If the slightest pressure is applied to the blister, it can break. Care should be exercised to maintain the integrity of the wood surface; a broken gallery is difficult to treat with insecticide.