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Carpenter ants

​​​​​​During the year, you may notice more carpenter ants around gardens and homes. These large (6 to 10 mm) black ants often become pests in their search for food. They can also damage wooden structures by eating their way through the wood to make tunnels for nesting.

What are their habits?

Carpenter ants eat both plant and animal matter. They enter houses through windows, holes in foundations, along power and telephone cables, tree branches, or by firewood that's brought inside.

Outdoors, carpenter ants are found in dead tree trunks, logs, and fence posts. They prefer moist, decaying wood. Nests can be found in wooden steps, wooden sills, and around porches.

If you find carpenter ants in your home, it may mean that you have a moisture problem or the ants are eating away at the wood your house is made of. If you see sawdust-like shavings and a lot of carpenter ants with wings inside your home it usually means you have a nest inside your home.

How do I control them at home?

  • Remove all decaying or infested wood from around buildings. Store firewood away from the sides of a building.
  • Make sure the humidity in the building isn’t too high.
  • Keep the floors clean. Sweep regularly to clean up food crumbs.
  • Use insecticides (baits, sprays, or dusts) on the nest and area around the nest. Make sure you read the label closely. Chemical control only works when used together with physical control methods.

If you’re using an insecticide (pesticide), make sure to read the label closely. Chemical control works best when used with physical control methods.

When to Hire a Professional

If the problem is bad, it’s best to hire a certified pest control professional. Do your research and choose one you can trust.​​​​​​

The professional should be able to tell you what’s causing the pest problem and come up with a plan to get rid of the pest. Tell the professional if you have children or pets. Several visits may be needed and it may take days or even weeks if the pest problem is really bad.

If you rent, you landlord must, by law, keep the home pest-free and hire a professional as needed. If your landlord doesn’t correct the problem, call Health Link at 811 to register a complaint for a health inspector.


To learn more, call your nearest Environmental Health office.

Current as of: March 15, 2018

Author: Environmental Public Health, Alberta Health Services