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Carpenter Ants

Carpenter Ants

If you live around trees, and many people do, you probably have carpenter ants around your home.


About Carpenter Ants

If you live around trees, and many people do, you probably have carpenter ants around your home. Carpenter ants are typically large ants, although the size of the workers can vary in a single colony. Finding a few carpenter ants in your home each week is not necessarily a sign that you have an infestation. Foraging ants roam far and wide looking for food and an occasional ant trapped in a sink or bathtub is quite common. If there are trees close to your home, ants can fall or be blown off the trees onto your roof. They may end up trapped within your home during their journey back to their nest.

Carpenter ants do not eat wood. They get their name from their habit of hollowing out wood in order to make a suitable nesting site. In addition to wood, carpenter ants will happily nest in Styrofoam (EPS) panels and other types of insulation. A good indication of a carpenter ant infestation within a home is the presence of numerous foraging ants, especially in the kitchen or bathroom. Water attracts carpenter ants as much as food and moist wood around leaky pipes and drains provides an ideal environment for nesting ants. Another sign of an infestation is the presence of large winged ants in late spring and early summer.

Most carpenter ant colonies start outdoors in a tree cavity. After a few years, the colony grows and expands its foraging territory. If suitable conditions are found within a nearby home, satellite colonies can become established in voids, moist wood or foam panels within the home. These satellite colonies contain workers, older larvae, pupae, and when conditions are right, some winged reproductive ants. Once a satellite colony has become established within a structure the potential for additional satellite colonies dramatically increases.

Control of a carpenter ant infestation starts with a complete and thorough inspection. Useful inspection tools include a flashlight, a thin bladed screwdriver for probing the wood and a stethoscope, if you have one. Since carpenter ants are most active at night, the best time to perform an inspection is after dusk. Two things to keep in mind during your inspection, find the voids and follow the water. Although carpenter ants are usually found in wood, any dark, damp cavity can provide a suitable nesting site. Carpenter ants make a noise like crinkling cellophane as they move about and a stethoscope makes them much easier to hear and locate. Tapping a suspected nest site excites the ants and you should be able to hear their movement.

When carpenter ants burrow into wood they generate sawdust, or frass, that can pile up beneath the site of their activity. Carpenter ant frass looks like tiny wood shavings and will often contain bits and pieces of dead insects. Look closely at all of the wood directly above any frass piles for signs of any openings. Probing the wood with a thin bladed screwdriver can reveal hollowed out nesting sites.

In addition to food and a nesting site, carpenter ants require water. That’s one reason they prefer to nest in damp wood. A moisture meter is a great tool to have for discovering actual and potential carpenter ant nesting sites as well as finding decay prone areas. Some pretty good moisture meters can be found on eBay or for less than $30. A moisture reading of over 20% is an indication of some type of water problem that needs to be corrected.


Correcting roof leaks, faulty plumbing, and water penetration into log walls are the most important steps for long-term carpenter ant control. Even after the leaks have been repaired, enough moisture may remain to sustain a carpenter ant infestation for many months. The application of a contact pesticide directly to the nest is not the best way to control carpenter ants. Most contact pesticides are highly repellent which causes the ants to scatter. This creates the potential for additional satellite colonies to become established in other areas of the home. In addition, contact pesticides do not impart any long term residual protection to the wood.

After a few months the carpenter ants may return to the site of their original nest. A better way to control a carpenter ant infestation is to treat the infested area and those areas subject to infestations with a borate such as Shell-Guard®, Shell-Guard RTU or Armor-Guard®. They are all effective pesticides for preventing carpenter ant infestations. Armor-Guard is best used as a dust in wall voids and other areas as preventative measure. Along with the use of a borate, you can try using a granular bait such as Amdro Ant Block around your home. It will help reduce the population of carpenter ants as well as other ants. Carpenter ants are not easily eliminated and you may wish to call a professional in to take care of the problem.

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