Termites are unique insects. Unlike most other insects, they feed on wood and live in large colonies. This ability to consume wood makes them among the most important structural insect pests in the Northwest.¹ There is no question that the thought of thousands of hungry insects consuming the structure of your house is frightening. Fortunately, you can take pesticide-free steps to help prevent termite damage to your house. If you already have an infestation, take time to make an informed decision about how to proceed.

Benefits of Termites

Subterranean termites are an important part of the world's ecosystems. Termites' recycling of wood and other plant material is crucial. Their soil tunnels help plant health by adding nutrients to the soil and making it more porous.² This knowledge is probably not much consolation when termites are recycling parts of your house.

Signs of Subterranean Termite Infestation

Finding shelter tubes is a sure sign of past or current subterranean termite presence. Timely discovery of tubes on foundation walls, piers, sills or joists can help you head off further damage.¹ Shelter tubes should be broken and removed when possible. This will interrupt termite access to your house. Broken shelter tubes will also allow ants to attack the colony.²

Swarms of winged termites emerging inside the home are a good indication of an infestation. Indoors, they do no harm and can be vacuumed up. Swarms emerging from the base of the foundation or adjoining porches and patios are also likely related to structural infestation.³

PREVENTION

Protecting Wood

Preventing conditions such as rot in structural wood or wood in contact with soil can deter a termite attack.¹ According to Washington State University, such steps can help to prevent structural infestations in many cases.¹ Make your house unattractive to termites by following these recommendations:^1,2 

• Make sure no wooden parts of your house are in contact with soil.
• Underneath your house, any wood should be at least 12 inches above the soil.
• Remove tree stumps, stored lumber, fence posts, wood debris, and buried scrap wood near your home. Include your crawl space if you have one.
• Stack firewood so that it is not in contact with siding or other wood parts of your house.
• Repair leaky pipes and dripping faucets. Be careful not to overwater near your house.
• Make sure downspouts carry water away from your house.
• Check for stucco siding that touches the ground, a condition that makes buildings particularly susceptible to infestation.
• Create good ventilation for better moisture control under the house. Vents in foundation walls provide better air circulation in crawl spaces than those placed between joists. Keep vent screens clean. Trim shrubs that are blocking your foundation vents.

Sand Barriers

Sand grains of the correct size (called 16 grit; with a diameter of 0.06 to 0.1 inches) can be used as a termite barrier because termites are unable to dig through or move sand grains of that size. A field test in northern California showed that installing a sand barrier 18 inches wide and 3 inches deep in crawl spaces along the inside of the foundation wall effectively stopped termites. For long-term success, these researchers recommended careful installation of the barrier and regular monitoring.⁴ Other particle sizes (10 to 16 grit) may also be effective.²

Sand barriers have been used successfully under concrete slabs. They are installed during construction before the slab is poured.⁴

Mesh Barriers

Stainless steel mesh can also be a successful termite barrier.⁵ These mesh barriers are installed during construction or remodeling and are currently commercially available in Florida, Texas, and Hawaii.⁶

Replacing Lumber

When replacing lumber in structures, consider using wood that is more resistant to termite attack. For example, for wood used in the West, Douglas fir is more resistant to damage than hemlock or spruce. The University of California's termite factsheet presents a table of the relative resistance of lumber to termites.¹

Least-Toxic Chemical Wood Treatments

Treated wood is often recommended for preventing termite damage. If you decide to use treated consider choosing borates, a chemical family that includes boric acid and borax. While wood treatments are toxic to termites and can discourage establishment of new colonies, regular inspection of the house is still needed because termites can reach untreated wood by constructing shelter tubes over treated surfaces.²

Pressure treated wood is usually recommended for use on foundations or on wood that is in soil contact. Wood treated with disodium octaborate tetrahydrate (a borate) is the least-toxic choice among pressure treatments.²

Wood treatments may also be painted or sprayed on exposed wood underneath the house, assuming that there's crawl space access. Borate products, such as Bora-care, are the least-toxic choice.² Bora-Care inhibits digestive enzymes, causing insects such as termites to starve. In a 2006 study by the Florida Department of Agriculture,⁷ Bora-Care’s efficacy was monitored for five years at 27 sites where termites were present. Only one of 27 structures (~4%) showed evidence of infestation within the 5 years following treatment with Bora-Care. While fumigation chemicals will dissipate after use, Bora-Care remains inside the wood to prevent future termite infestations. 

TREATMENT

No Need to Rush

You do not need to rush into a decision about how to deal with a subterranean termite infestation (unless your house is on the market.) Termite infestations develop over years and wood damage occurs slowly.⁸ Taking time to make an informed decision will not make a significant difference in the amount of damage.³

Making an Informed Decision

Most homeowners who find subterranean termite infestations opt to use a chemical treatment to protect their home, In addition to taking protective measures. The two basic chemical treatments — soil application and bait stations — differ dramatically in the amount of pesticides used. A soil treatment may use hundreds of gallons of liquid termiticide. By contrast, bait stations employ small amounts that are confined in bait stations.⁶

NCAP does not recommend using pesticides. If you feel that pesticide use is unavoidable, however, consider using termite baits that offer the advantage of using only small amounts of pesticide.

In either case, termite products should be applied by a pesticide control company. Interview companies about their experience and get references. Check for complaints with appropriate state agencies or business bureaus. Look for an established firm with experienced technicians.³

Chemical Control Methods

Understanding the basics of chemical treatments can help you make an informed choice. You can also learn about the toxicity of the chemicals to be used for termite control.

Fumigation chemicals can have lasting detrimental effects to people, especially those with compromised immune systems, pets, wildlife and the environment. After the fumigation process is completed, toxic gases get released into the air from the home. One of these gases, sulfuryl fluoride, contributes to climate change.

Soil treatment

Liquid termiticides are applied to soil along the foundation, both outside and under the house, around supporting piers, and under concrete slabs. The goal is to have an uninterrupted barrier. Some barrier termiticides work by repelling termites, while other newer chemicals are toxic to termites, killing them as they tunnel through. Treatments are supposed to last five years. However, it can be difficult to create an unbroken barrier and termites can slip through very small, untreated gaps.³

Botanical Oils

Some pest control companies now have botanical oil options available for treating termites. D-limonene, a compound found in orange oil, is marketed as an effective treatment for drywood termites. Neem oil is used for subterranean termites to prevent molting and multiplying. Both would need to come in direct contact with or be ingested by the termites. No published scientific studies have yet been conducted on botanical oils and termites, so NCAP cannot speak to the effectiveness of botanical oils at this time. (Read more about orange oil and termites in the IPM Practitioner here.)

Bait stations

With baits, plastic cylinders or stakes are installed in the ground at fixed intervals around the house and yard. Initially, wood is usually placed inside to attract foraging termites. Periodic inspections by the pest control company determine when termites are present. At that point, the wood is replaced with termiticide-laced cardboard or other attractive material. Bait stations may also be placed above ground over an active shelter tubes or directly over infested wood, drywall, etc. The chemical baits are slow-acting poisons that get taken back to the nest and passed along to other termites.⁷

Suppression of termite populations with baits can take longer than liquid treatments because of the time needed for termites to "find" the bait stations. This can vary widely by location for reasons that are not well understood.⁸ Adding extra stations can boost the likelihood of bait stations being found. Time of year can also affect success; termites are more active in spring through fall.

Baiting may be more expensive than conventional barrier treatments because of the need for monitoring and re-baiting, not just in the initial stages but also in subsequent years. However, baits have the potential to affect multiple nesting sites including those outside the house.³

Non-Chemical Methods that Don't Work

Subterranean termites cannot be controlled by extreme temperatures such as heating and freezing or by electrocution devices.²

IDENTIFICATION

Termites or Ants?

You may already suspect that you have termites in your house. You'll need to decide if the insects you've found are really termites. Termites and ants are often confused. Take a careful look at the antennae and "waist." Ants have elbowed antennae and narrow waists while termites have straight antennae and thick waists. Both ants and termites are occasionally winged, but termite wings are unique because the front and the hind wings are the same size.¹

Which Termite?

Next you'll need to decide which termite is causing your problem, because managing different termites requires different techniques.

Three groups of termites — dampwood, drywood, and subterranean — are found in the United States, and they share certain characteristics. They are social insects that sometimes live in extensive colonies. Different "castes," such as soldiers and workers, differ somewhat in size and appearance. Periodically, new queens and kings (reproductives) swarm out of an established nest, flying to find a new nesting site.²

Dampwood termites, are mostly found in the Pacific Northwest and California.² They live in very moist wood (not soil), including beach houses located in cool humid areas. These large termites are 1/2 to 3/4 inch long. Winged reproductives can exceed 1 inch in length including the wings.¹ Dampwood termites found in Florida are only incidental pests of structures.⁴

Drywood termites are found across the southernmost part of the Unites States as well as part way up both the east and west coasts.⁹ They nest entirely above ground and don't require soil contact or much moisture.^{2</sup They are visibly larger than subterranean termites.2}

Subterranean termites are found throughout the United States (except Alaska), with the highest concentration found in the South.⁹ Subterranean termites are small. The grayish-white workers are 3/16 inch long. The winged reproductives are dark brown to brownish black and are about 3/8 inch long, including wings. The soldiers, with grayish white bodies, cream-colored heads, and black jaws, are about ¼ inch long.¹

Subterranean termites require moist conditions and nest in or near the soil. They feed on wood that is in contact with soil or else they construct shelter tubes that extend from the soil to reach above ground wood. The tubes are made of soil mixed with bits of wood or other materials. These mud tubes help the termites stay moist and offer protection from predators.²

Swarms of winged reproductive termites may be seen on warm sunny days in the spring or fall after a rain. After settling on the ground, they shed their wings and then pair up to mate. Most don't survive long enough to establish a colony.³

The Living With Bugs website has a map of the United States showing areas of subterranean and drywood termite infestations.⁹

Inspections

To minimize termite problems in your home, regular inspections are important. Hiring a qualified professional is probably advisable.² If you choose to do it yourself, you'll need to inspect structural wood near your foundation and crawl space, if your house has one. Wear gloves, coveralls, and a hat. Use a sharp pick or screwdriver to test for damaged beams, joists, and sills. Wood damaged by subterranean termites may be dark or blistered and is easily punctured. Look for shelter tubes on foundation walls and other surfaces.¹

For expert advice tailored to your pest or weed issues, check out our sliding scale Pest and Weed Management Consultation services.

References

1. Antonelli, A.L. 2002. Termites: Biology, prevention, and control. Washington State Univ. Cooperative Extension. http://owic.oregonstate.edu/sites/default/files/pubs/termites.pdf
2. Univ. of California. Agriculture and Natural Resources. 2001. Termites. Pest Notes Publ. 7415. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7415.html
3. Potter, M. 2004. Termite control: Answers for homeowners. University of Kentucky. College of Agriculture. Entomology. http://www.ca.uky.edu/ENTOMOLOGY/entfacts/ef604.asp
4. Lewis, V.R. et al. 1996. Field comparison of sand or insecticide barriers for control of Reticulitermes spp. (Isoptera: Rhinotermitidae) infestations in homes in northern California. Sociobiology 28(3):327-336.
5. Kard, B. 1999. Mesh may fit in as a termite barrier. Pest Control (Feb.)
6. Termimesh. Undated. Termimes - the company. http://www.termimesh.com
7. Daiker, D.H., Ferguson Foos J. 2006. Termiticide efficacy review for Bora-Care wood treatment (disodium octaborate tetrahydrate). Florida Dept. of Agriculture and Consumer Services. https://www.fdacs.gov/content/download/31414/file/Efficacy%20Review%20Bora%20Care%203-03-06.pdf
8. Potter, M 2004. Termite baits: A guide for homeowners. University of Kentucky. College of Agriculture. Entomology. http://www.ca.uky.edu/ENTOMOLOGY/entfacts/ef639.asp
9. DeAngelis, J. 2009. Drywood termite (Kalotermitidae). LivinginwithBugs.com http://www.livingwithbugs.com/drywood_termite.html
10. Scheffrahn, R.H. and Nan-Yao Su. 2007. Featured creatures: Florida dampwood termites. University of Florida Inst. Of Food and Agricultural Sciences and Florida Dept. of Agriculture and Consumer Services. http://edis.ifas.ufl.edu/in369

This article was originally published as:
Cox, Caroline. 2004. Protecting your home from subterranean termite damage. Journal of Pesticide Reform 24(3):6-7. Revised 2009 by Kay Rumsey, botanical oil section and links updated in July 2017.