Termites: Identification, Prevention and Control

Prevention Use an integrated program to manage termites. Combine methods such as modifying habitats, excluding termites from the building by physical and chemical means, and using mechanical and chemical methods to destroy existing colonies. Building design may contribute to termite invasion. Keep all substructure wood at least 12 inches above the soil beneath the building. Identify and correct other structural deficiencies that attract or promote termite infestations. Keep attic and foundation areas well ventilated and dry. Use screening over attic vents and seal other openings, such as knotholes and cracks, to discourage the entry of winged drywood termites. Although screening of foundation vents or sealing other openings into the substructure helps block the entry of termites, these procedures may interfere with adequate ventilation and increase moisture problems, especially if a very fine mesh is used in the screening. Termite-resistant wood and other building materials may aid in reducing damage. Chemical treatment of structural wood used in foundations and other wood in contact with soil helps protect against termite damage in areas where building designs must be altered or concrete cannot be used. Inspect utility and service boxes attached to the building to see that they are sealed and do not provide shelter or a point of entry for termites. Reduce chances of infestation by removing or protecting any wood in contact with the soil. Inspect porches and other structural or foundation wood for signs of termites. Look for and remove limbs and tree stumps, stored lumber, untreated fence posts, and buried scrap wood near the structure that may attract termites.Recent research has proved the effectiveness of foundation sand barriers for subterranean termite control. Sand with particle sizes in the range of 10 to 16 mesh is used to replace soil around the foundation of a building and sometimes in the crawl space. Subterranean termites are unable to construct their tunnels through the sand and therefore cannot invade wooden structures resting on the foundation. Controlling Drywood Termites Drywood termite colonies are usually small, making it possible at times to control them by removing and replacing damaged wood. However, more than one colony may exist in a structure. Destroy damaged and infested wood promptly, preferably by burning if this is allowed. Otherwise, transport the material to a sanitary disposal site. Other control methods that may be used by pest control professionals include freezing with liquid nitrogen, electrical treatment, fumigation, or spot treatment of galleries by injecting them with insecticides. The use of heat is another means of controlling drywood termites that shows promise and may reduce or eliminate the need for insecticides. A comprehensive study on the advantages and disadvantages of each method has been completed and results will be forthcoming. Controlling Subterranean and Dampwood Termites Subterranean and dampwood termites cannot be properly controlled by fumigation, heat treatment, freezing, or termite electrocutor devices because the reproductives and nymphs are concentrated in nests near or below ground level in structures, out of reach of these control methods. For subterranean termites, whenever possible, destroy shelter tubes to interrupt access to wooden substructures and to open colonies to attack from natural enemies such as ants. For dampwood termites, if infestations are small, destroy accessible nests by removing infested wood. Spot-treat subterranean and dampwood termite nest areas with a liquid formulation of a long-lasting insecticide. Removing excess moisture from wood will also destroy dampwood termite nests. If colonies are numerous or inaccessible, hire a pest control professional to apply soil drenches of a long-lasting (3 to 7 years) liquid insecticide directly under the building or injected through the foundation or beneath concrete slabs. When insecticides are selected, it is important to choose the least toxic material, yet one that will still be effective. Confine insecticide use to areas where termites are detected and to inaccessible areas. Chlorinated hydrocarbon insecticides, such as chlordane, have been used extensively for subterranean termite control because of their long persistence--30 years or more in the soil. Persistence and suspicions of health-related problems, however, have caused chlordane to be removed from the market. Pyrethroid and organophosphate insecticides, usually considered short-lived, are now being developed that will persist in soil for nearly 10 years. Foundations and structural wood can be protected by injecting insecticides into the soil beneath structures by horizontal or vertical drilling and rodding. Special hazards are involved with applying insecticides to the soil around and under buildings and termite control should be carried out by a licensed professional. Soil-applied insecticides must not leach through the soil profile to contaminate ground water. The mobility of insecticides in the soil is a chemical property that is influenced by soil type, weather, and application techniques. Applications in the wrong place can cause insecticide contamination of heating ducts, radiant heat pipes, or plumbing used for water or sewage under the treated building. Experimental efforts have been made to control soil-dwelling termites using biological control agents, including use of argentine ants and nematodes. However, these methods are not yet effective enough to be recommended. IPM Education and Publications, Statewide IPM project University of California DANR Compiled from: Marer, Patrick. 1991. Residential, Industrial, and Institutional Pest Control. 1991. Univ. Calif. Agric. Nat. Resources Publication 3334. Oakland. Editor: B. Ohlendorf Technical Editor: M. L. Flint.

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