Sniffing Out Termites
From trained dogs to high-tech listening devices, how to detect — and deter — these wood-eating pests
Dogs trained to sniff out termites in their hiding places are just one way to find out if your house is infested.
Nationwide, termites inflict more than $2.5 billion worth of damage on homes each year. Crawling up into sill plates or foundation posts from damp soil, flying into attics or crawl spaces, these relentless insects tunnel into and eat wood, leaving nothing but paper-thin layers where strong supports used to be.
Much of that damage could be avoided with early detection. But termites dine out of sight, cleverly disguising the results of their munching. That's what makes them so scary — and so costly to control. On the following pages, we'll tell you the warning signs to look for, the most common types of termites, and the pros and cons of various treatment options.
You can check for termites yourself, but a licensed pest-control professional knows where to look for infestations and has the equipment and experience to properly identify bugs, the first step toward eradicating them. (Accurate identification is crucial: What works on one type may not affect another.) Ask to see evidence of an active colony; damaged wood by itself may not be sufficient proof that termites are at work. And once you've gotten rid of them, sign up for an annual inspection; you don't want them to get far if they ever come back.
Subterranean termite as swarmer
What's Eating Your House?
Many homeowners discover they have a termite problem when they see a stream of swarmers emerging by the hundreds from a tiny crevice and flying off to form a new colony. Other signs of trouble are harder to spot. The workers, the bugs that actually eat the wood, are visible only if you break into their tunnels or galleries, as are the soldiers that guard the nest.
Of the dozens of termite species in the U.S., the three shown below do the most harm. A fourth type, the dampwood termite, poses less of a threat: Their colonies are small, and they only nest in wet wood. Eliminate the source of the dampness, and the colony dies.
Habitat: All states except Alaska.
Habits: Nests underground; uses mud tubes to reach wood in the house. Colonies range in size from several hundred thousand to a million. Workers will eat through plaster, foam, plastic, or asphalt to get to wood.
Habitat: Southeast, Southern California, Hawaii.
Habits: This voracious variety of subterranean termite forms large colonies of several million and can structurally damage a house in months (other termites take years). Nests underground, but also builds satellite nests in trees and houses.
Habitat: Gulf Coast, Southwest, Hawaii.
Habits: Small colonies can live anywhere in a house. Needs no contact with ground.
What to Look For
Pencil-thick to inch-wide tunnels on foundation and crawl-space walls (above) shelter subterranean termites traveling to and from the nest. If you see cream-colored insects when you break open the tubes, your house is infested. If you don't, the colony may be dead or using another route inside.
Streams of winged termites indoors (or piles of shed wings) almost always means your house is infested. Seeing them outdoors is not necessarily cause for alarm.
Most termites prefer moist habitats: next to foundations or masonry, beneath leaking gutters, or near overgrown bushes. Look for bits of mud or dried dirt in the galleries they hollow out.
Termites chewing into dry wood usually leave a thin veneer, which may appear blistered or dark and breaks through easily when pressed.
Bulging Floors, Ceilings, or Walls
Formosan termites may be building satellite nests between joists or studs. Ridges on wallpaper could be tunnels for subterranean termites.
Holes and Droppings
Pinholes with piles of sand-grain-size pellets indicate drywood termites. Bigger holes may be signs of powder-post beetles or carpenter bees.
Tools of Detection
Acoustic Emission Detector
Picks up the sound of termites ripping apart wood fibers. The detector must be placed within a foot or two of where termites are feeding.
Sniffs for methane and also carbon dioxide. Tests show mixed results for accuracy.
Pinpoints areas with high moisture levels — 15 percent or above — which are more likely to harbor some types of termites.
Ice Pick or Screwdriver
The most common tool. Used to probe for soft or hollow spots.
Scans and detects elevated moisture levels inside intact walls. When used in combination with a heater, can also make termite galleries visible.
Works like radar to detect termites moving through wood and under drywall or tile.
With its flexible shaft and fiber-optic light, this instrument allows inspectors to peer through a small hole into hollow walls.
Useful in houses with inaccessible crawl spaces or slab foundations, where termites can sneak up through cracks into interior walls. Most any breed can be trained to sniff out the methane termites emit as they digest wood.
Mud tubes on foundation and crawl-space walls signal termites.
Pick Your Poison: Common Treatment Options
Until recently, the only way to get rid of termites was with nasty toxic pesticides, many of which are now banned or being phased out. Today's chemicals are safer — some even approved for homeowners to apply — although they don't last as long.
Targets: Subterranean and Formosan termites
How It Works: Termites take pesticide from in-ground stations buried around the house and carry it back to the nest. Eventually the entire colony dies. Professionally installed baits are monitored monthly during an infestation and four times a year after that.
Pros: No poisons or drilling in the house. Uses little pesticide, which remains in a tamper-resistant container. Can protect inaccessible areas.
Cons: May take months to work. Termites can infest a house before finding bait. DIY versions lack the reliable monitoring and more effective baits of pro systems.
Cost: About $1,200-$2,800 to install, plus about $250-$350 for annual follow-up inspection
Targets: Subterranean and Formosan termites (also carpenter ants, many wood-boring beetles, and rot fungi)
How It Works: Operator sprays exposed bare wood with a boron solution or fills enclosed wall cavities with boron-laced foam. Not toxic to people and most mammals.
Pros: Provides permanent protection. Doesn't smell or change the look of wood. Easy for homeowners to apply.
Cons: Take weeks to work. Hard to reach exposed wood in existing houses. May leach out if wood contacts soil.
Cost: About $800-$1,500 for pro treatment. About $15 for 1-lb. bag (treats 200 square feet)
Targets: All termites
How It Works: Operator drills into wood or cavities where termites are feeding or nesting, then applies a foam or liquid pesticide. Generally used in conjunction with other treatments.
Pros: Confines pesticide to the places it's most needed. Works quickly.
Cons: Can miss areas where termites are active. Holes need patching after treatment.
Cost: About $250 and up
Targets: Drywood termites (and many wood-boring beetles)
How It Works: Operator tents the entire house with tarps and injects poison gas. Look for fumigators who use sulfuryl flouride, which, unlike its predecessor methyl bromide, doesn't deplete the ozone layer and leaves little residue and no odor.
Pros: Usually 100 percent effective.
Cons: Family and pets must move out for two nights; food and medicines must be bagged. Offers no residual protection.
Cost: About $750-$2,000
Targets: Subterranean and Formosan termites
How It Works: Operator pumps a continuous chemical barrier into soil around and under the house. Repellent pesticides only keep termites away. More costly nonrepellents can kill the entire colony.
Pros: Works fast. Protects for at least 5 years.
Cons: Uses many gallons of pesticide. May affect nearby wells and waterways. Repellents leave a smell temporarily.
Cost: About $800-$1,500 plus about 10 percent of initial cost for annual renewal and inspection
Acoustic emission detector
For those reluctant to use pesticides of any kind in or around the house, a few nontoxic termite treatments have been developed, primarily to treat drywood termites. While free of noxious residues, these methods are not widely available and, unlike pesticides, lack any long-term protection against reinfestation.
Eradicates drywood termites, the satellite nests of Formosan termites, and many wood-boring beetles. The house is wrapped in a tent (the same as for fumigation), then hot air is pumped in until the center of the framing lumber reaches 120° for at least half an hour. The treatment is fast — one day from start to finish — and the house can be reoccupied immediately. Plastics that are sensitive to heat, including vinyl windows, have to be protected or removed.
Cost: $1,200 to $6,000; more if the windows are vinyl.
Exterminators send high-voltage discharges through the wood and fry any termites present. (The same tool can also be used to find termite-weakened wood.) Effective as long as all the colonies are discovered. Only able to treat exposed wood. Nearby metal, concrete, or soil may interfere with the process.
Cost: $500 to $650 for spot treatment; $1,200 to $2,500 for the whole house, including warranty and associated follow-up inspections and treatments.
Making Termites Feel Unwelcome
What you can do:
• Clean overflowing gutters and use splash blocks to divert water away from foundation.
• Trim shrubbery clear of house.
• Isolate wood from concrete or masonry with an air space or flashing.
• Keep wood mulch away from wood siding or trim.
• Store firewood off the ground at least 15 feet from the house.
• Don't bury scrap wood or leave tree stumps in the vicinity of the house.
• Fix leaks immediately.
A house is swaddled in fabric before being filled with toxic gas. Fumigation works against drywood termites and the satellite nests of Formosan termites.
Where To Find It:
Our thanks to —
Dr. Michael Potter
urban entomologist at the University of Kentucky and contributing author
The Mallis Handbook of Pest Control (GIE Publishing)
University of Kentucky
Technical Direct for the National Pest Management Association
Dunn Loring, VA
Tools of Detection —
Acoustic emission detector:
Dunegan Engineering Company, Inc.
San Juan Capistrano, CA
Loyal Termite & Pest Control Inc.
Loyal Termite & Pest Control.
Pick Your Poison —
Dow AgroSciences LLC
Bora-Care Termite Insecticide
DIY Pest Control
DIY Pest Control
The Terminix International Company LP
Nonrepellent Soil Drench:
Poison-Free Alternatives —
W.A. Stone Termite & Pest Control Inc.
Esconco, CA 800-559-7999
Las Vegas, NV
Hydrex Pest Control Co.
San Diego, CA
Ecola Services, Inc.
Mission Hills, CA
For Further Information:
To learn about the habits of termites in your area and state pesticide regulations, contact your state university or local cooperative extension service.