Subterranean Termites

The three principal types of termites in Florida are subterranean (nest in the soil), dampwood (infest damp wood), and drywood termites (infest dry wood).

Subterranean termites are the most destructive and frequently encountered kind of termite found throughout the state.

Although they nest in soil, subterranean termites can attack structures by building tubes that connect their nest to wood elements in structures. Aerial nests can occur without a ground connection if all castes of the colony are present and moisture is available.

Subterranean termites feed on wood or other items that contain cellulose, such as paper, fiberboard, and some fabrics derived from cotton or plant fibers. Termites have protozoa in their digestive tracts that can convert cellulose into usable food.

Subterranean termites nest in the soil to obtain moisture, but they also nest in wood that is often wet. They easily attack any wood in contact with the ground. If the wood does not contact the soil, they can build mud tunnels or tubes to reach wood several feet above the ground. These tunnels can extend for 50-60 feet to reach wood and often enter a structure through expansion joints in concrete slabs or where utilities enter the house.

Detection of Termites

Termites remain hidden within wood and are often difficult to detect. However, subterranean termites may be detected by the presence of winged reproductives, mud tubes, and wood damage.

Winged Reproductives

Winged reproductives emerge from colonies in great numbers usually in the spring and during the daylight hours. Usually termites are first noticed by the presence of winged reproductives. Mating occurs during these flights, and males and females form new colonies. Winged termites can be distinguished from flying ants by their thick-waist, straight antennae and wings of equal size.

Large numbers of winged termites in a house are an indication of probable infestation. Termite wings break off shortly after their flight, and even though the actual swarming is not observed, the presence of discarded wings indicate that a colony is nearby. Because termites are attracted to light, their broken-off wings are often near doors or windows where the termites have been attracted to the light.

Winged termites emerging from the ground out-of-doors near the house does not necessarily mean the house is infested, but it is a good reason to check further. Termites in structures usually come from colonies already established in the soil.
Peak swarming periods for subterranean termites are from January through May in Florida. They may also swarm to a lesser extent during the other months.

Mud Tubes

Subterranean termites build earthen, shelter tubes to protect them from low humidity and predation. These tubes are usually 1/4 to 1 inch wide. Houses should be inspected at least once a year for evidence of tubes. If the house has a crawl space, the inside and outside of foundations should be inspected for tubes. If the house has a concrete slab floor, cracks in concrete floors and places where pipes and utilities go through the slab should be closely examined. Cracks in concrete foundations and open voids in concrete block foundations are also hidden avenues of entry.

Wood Damage

Wood damaged by subterranean termites is often not noticed because the exterior surface usually must be removed to see the damage. However, galleries can be detected by tapping the wood every few inches with the handle of a screwdriver. Damaged wood sounds hollow, and the screwdriver may even break through into the galleries.

Subterranean termite feeding follows the grain of the wood and only the soft springwood is attacked. Unlike drywood termites or other wood-boring insects, subterranean termites do not push wood particles or pellets (fecal material) to the outside, but rather use it in the construction of their tunnels. This debris, along with sand and soil particles, is used as a form of plaster.


Subterranean and drywood termites require completely different control methods; therefore, the termites must be correctly identified.
Subterranean Termite Prevention and Control

The best control of subterranean termites is prevention. The best time to provide protection against termites is during the planning and construction of a building. Prevention should include:

• Removal of all stumps, roots, wood, and similar materials from the building site before construction is begun.

• Removal of all form boards and grade stakes used in construction.

• There should be no contact between the building woodwork and the soil or fill. Exterior woodwork should be located a minimum of 6 inches above ground and beams in crawl spaces at least 18 inches above ground to provide ample space to make future inspections.

• Ventilation openings in foundations should be designed to prevent dead air pockets and of sufficient size to assure frequent changes of air -- at least 2 sq. ft. to 25 running feet of outside foundation wall. This helps keep the ground dry and unfavorable for termites.

• Landscape plants and irrigation should not be placed within two feet of the foundation wall.

• Thorough annual inspections should be conducted to discover evidence of wood damage or termite activity such as shelter tubes on foundation surfaces, discarded wings or adult termites.

• Any wood that contacts the soil, such as fence posts, poles and general foundation structures, should be commercially pressure treated, and should not be attached to a structure.