How to Control the Wood-Destroying Carpenter Ant

Carpenter ants: camponotus laevigatus impact on wood.
Carpenter ants will tunnel into and destroy wood. Oxford Scientific/Oxford Scientific/Getty Images

If you've seen a large ant in your home, especially in the spring or fall, it is very likely that is a carpenter ant. If the ant has wings, there is very little doubt that it is a carpenter ant.

Carpenter ants are common across the U.S. and are the largest of all common ant species. However, size will vary, even within a single colony and type: worker ants can be 1/4 inch up to 5/8 inch. A colony's queen can be as large as 1 inch in length. But carpenters do tend to be more similar in color than in size - with most being dark brown to black, with some having a reddish or yellowish hue.


8 Ways to Differentiate Between Carpenter Ants and Termites

One of the most obvious signs of a carpenter ant infestation is the sighting of winged ants in the home. Although these ants can originate outside the home, if they find some nice, soft decaying wood in your home into which they can tunnel and begin to build a colony, they are likely to stay unless you rout them out!

If the flying ant is seen outdoors away from the home, particularly in moist or wooded areas, it may not be of significant concern. However, it is prudent to ensure any nests are well away from the home's structure and to take precautions to keep the ant colony from expanding to the home.

Chemical Treatment for Carpenter Ants

Because ants generally infest a structure from an outdoor nest, a perimeter treatment – the application of a granular or liquid insecticide to an area about 2- to 4-feet wide all around the perimeter of the home with a product labeled for control of carpenter ants can provide some control. Application should be made in the spring and fall following all label directions.

Additionally, carpenter ants will travel across wires, branches and limbs, so all trees and shrubs should be trimmed away from the home, and all wire and cable openings caulked or otherwise sealed against pest entry

The most effective way to treat for carpenter ants is to find their nest – or nests – and apply a chemical insecticide directly into it and along tunnels and trails. This is most effectively done with a dust formulation, because even if the dust doesn't immediately contact all the ants, foraging ants will carry it back to the nest on their bodies. To treat within walls where a nest is suspected or ants are seen entering or leaving, drill small holes (about 1/8 inch) and apply a dust such as boric acid, which is available at home or hardware stores.

Non-Chemical Control of Carpenter Ants

Getting rid of carpenter ants - and keeping them out - also means ferreting out the damaged wood in which they began to build their nest and removing it. In fact, you can often avoid chemicals altogether by replacing any wet and damaged wood in which the carpenter ants are nesting and repairing conditions causing the damage - such as roofing or plumbing leaks or other moisture issues. For more information, see Control the Winged Carpenter Ant.

Bait for Carpenter Ants

However, because there can be multiple nests, it can be difficult to locate them all, particularly the main nest which is often outdoors. For this reason, insecticide baits can be effective for carpenter ants.

Although termites eat the wood they infest, carpenter ants do not eat wood; they chew through it to create their nests and tunnels. When placed where ants are seen to forage, the foraging ants will carry it back to the nest to feed the colony.

Additionally, outdoor nests can be sprayed or drenched with an insecticide.

When using any insecticide:

  • Read and follow all label directions.
  • Never place where it may be accessible by children, pets, or non-target wildlife.
  • Do not use more than called for on the label. More is not better.
  • Do not use for any purpose or pest that is not listed on the label.
  • Be sure to follow any safety precautions, such as wearing gloves, etc.