How to Get Rid of Carpenter Ants Without Pesticides

Macro photo of a Carpenter ant, Camponotus herculeanus
Henrik_L / Getty Images

Most species of ants are little more than nuisances around the home. Most do not bite or sting except defensively or by accident, and they are not notable carriers of disease in the same way as houseflies and cockroaches. However, carpenter ants (Camponotus spp.) do not share the same harmless reputation, as these relatively large ants create nests by hollowing out decaying wood. If that wood happens to be found in the structural framing members of your home, the result can be a very serious weakening of your home's walls.

It's important to note, though, that carpenter ants do not actually eat wood in the way that termites do. Carpenter ants simply remove wood that is already decaying in order to establish colonies. If the soft, rotting wood is removed and replaced, the ants will disappear almost instantly in search of new nesting areas.

Identifying Carpenter Ants

The presence of ants is a serious problem only if you have the wood-damaging carpenter ants, so it's important to be able to distinguish them from similar ant species.

Carpenter ants average about 3/8 inch in length but can range from about 1/4 to 1 inch. This makes carpenter ants among the larger species of ants, but size alone is not an indicator, as there are several other types of ants of similar size. You may need to examine an ant closely under a magnifying glass to verify that its identity. The main indicators include a smooth, rounded back and a narrow, pinched waist with a small hump.

These details, along with a relatively large size, indicate you're dealing with carpenter ants. Other signs of carpenter ants are behavioral:

  • You may hear the carpenter ants in the walls, especially at night. The crackling sound is created by many ants gnawing on decaying wood.
  • You may see small piles of sawdust (called frass) at the base of foundations below entry points to the hidden colonies. This is the wood material the ants have excavated in order to tunnel into soft wood and create galleries for nesting.
  • In the springtime and early summer, you may see flying carpenter ants, adults that are leaving the nest to mate. A notable swarm indoors often indicates a serious infestation in walls. Other ant species also fly at certain times of the year, but this behavior often occurs later in the year than it does with carpenter ants.

4 Ways to Get Rid of Carpenter Ants Without Pesticides

Ants, in general, are not very susceptible to chemical pesticides. Most control methods for carpenter ants will appeal to green-minded homeowners.

Identify and Replace Bad Wood

The most surefire way to get rid of carpenter ants is to locate and remove the soft decaying wood that they use for nesting areas. This can be no easy feat since the affected wood is often hidden inside walls behind siding or wallboard. But you can often make an educated guess regarding likely locations for a carpenter ant colony. Walls where plumbing pipes are located are prime locations, since moisture condensing on cold water pipes can often introduce rot into walls. Framing members and sills around windows and doors are also prime locations, as are eave locations. Any area where you suspect moisture is found is worth examining if you see signs of carpenter ants in or around your home.

Replacing bad wood should go hand-in-hand with fixing whatever problem allowed moisture into the walls in the first place. Insulate water pipes to correct condensation issues. Make sure flashings around windows and patio doors are in good shape. Unless you correct the source of moisture, decay will eventually return, once more providing a tempting nesting area for carpenter ants.

Set Borax Ant Bait

As with other ants, an effective control method for small infestations of carpenter ants is to bait them with a sweet substance laced with borax. Worker ants that feed on this bait carry it back into the colony, where other ants eat it and die.

Borax is regarded as a non-toxic, organic control since it is a naturally occurring mineral. It works by interfering with the digestive process of the insect, but it can take several weeks of systematic baiting to eliminate an entire colony.

It's also possible to treat carpenter ants with a refined and concentrated form of borax, known as boric acid, which can be injected directly into the colonies as a fine dust or spray. But while boric acid is not strictly speaking a chemical pesticide, neither is it regarded by purists as an organic product, since boric acid is produced through heavy refinement.

Use Desiccating Dust

Desiccating dust, such as diatomaceous earth (D.E.) and silica gel, destroy insects by absorbing their waxy outer coating, causing them to die from dehydration. D.E. should be blown with a bulb duster behind electrical switch plates and into wall voids. Silica gel combined with the natural pesticide, pyrethrin, is available in aerosol cans and should be sprayed into the same areas as D.E.

Spray With Pyrethrin

While pyrethrin is technically a pesticide, it is an acceptable choice for many green-minded homeowners since pyrethrin is a natural substance obtained from chrysanthemum flowers. Pyrethrin works by stimulating the insect's nervous system, causing paralysis and death. It is an effective control for many insects and is a staple in the arsenal of many organic gardeners. Pyrethrin is applied by locating the nest, drilling holes, then injecting the spray directly into the colony.

Avoid pesticides labeled as pyrethroids, since these products typically blend pyrethrin with other chemicals to increase their effectiveness. Pyrethroids are not as safe as pure pyrethrin, so you must use them carefully. Pesticides with names such as deltamethrin, cypermethrin, bifenthrin, or gamma cyhalothrin are pyrethroid compounds that don't qualify as organic pesticides.

Warning

Pyrethrin, while considered safe for use around humans and pets, is still categorized as a neurotoxin, and as such, it should be used with care. Some people—especially asthma sufferers—are known to have allergic reactions to pyrethrin. Accidental ingestion by people or pets should prompt an immediate call to a poison control center or your veterinarian.

What Causes Carpenter Ants?

In the natural world, carpenter ants are important decomposers of forest trees, burrowing within dead wood to nest. But they will readily move from their native woods to the structures of homes looking for water and human or pet food. Like other ant species, carpenters feast largely on the parts of other insects, and on sweet substances, such as the sticky honeydew excretions of aphids—or spilled sugar on the countertop in your home.

Careful examination of dead trees or old wood piles on your property may reveal carpenter ant colonies. If these outdoor colonies are located within 300 feet of your home, there is a distinct possibility that carpenter ants will eventually find their way into your house's framing.

How to Prevent Carpenter Ants

Periodically inspecting your home for decaying wood and replacing it will usually prevent carpenter ants from gaining a foothold. All siding and foundation holes must be sealed and rotted wood replaced, especially next to drains and gutters; any wood that contacts soil should be capped with metal. In areas where carpenter ants are prevalent, it's possible to choose borate-treated lumber for wall framing and siding to discourage insect infestations.

Make sure your yard and nearby property are free of dead trees, stumps, and old woodpiles that may harbor nearby colonies. Store firewood outdoors, except for the small quantities you will use quickly. Before carrying the wood indoors, shake or knock it to dislodge loose insects.

Carpenter Ants vs. Termites

Homeowners very often confuse carpenter ants with termites, since the structural damage they cause can be similar. But termites actually consume wood, while carpenter ants merely tunnel through it to create nests. The presence of fine wood dust around the entry point to the nest is a strong sign you are dealing with carpenter ants rather than termites.

Visually, you can distinguish carpenter ants by their narrow, constricted waist, which is not present in the more cylindrical body of the termite. Finally, termites have straight antennae, not the jointed antennae found in carpenter ants.

FAQ
  • Do Carpenter Ants Bite?

    While carpenter ants have strong jaws for tunneling through wood, deliberate biting of humans or pets is rare. These are not blood-feeding insects, so they do not go out of their way to bite. If you are accidentally bitten, though, you will find the experience painful.

  • Do Carpenter Ants Carry Disease?

    There is the potential for carpenter ants to track bacteria around your house, but these insects feed primarily on other insects and plant juices. Like other ant species—and unlike houseflies and cockroaches—carpenter ants are not considered serious vectors for transmitting disease.

  • Are Some Regions Free of Carpenter Ants?

    Carpenter ants comprise more than 1,000 species in the Camponotus genus, but they are relatively rare in non-forested regions, such as arid climates and high mountains. The most prevalent species, the black carpenter ant (Camponotus pennsylvanicus) is found in almost all forested regions east of the Rocky Mountains, including urban areas with tree-filled landscapes.