Carpenter ants are one of the most common and problematic ants in Canada.
Why are carpenter ants a problem?
Carpenter ants cause more damage to wooden structures in Canada than any other pest. They excavate extensive tunnels or galleries in wood to create nests. (They don't eat wood.) The tunnels weaken the wood of floor joists and load-bearing timbers, thus compromising the structural integrity of your home or business.
What do carpenter ants look like?
Carpenter ants are larger than most ants in Canada. Here are their key characteristics:
- Size: 6. to 25 mm or 3/8 to 1 inch
- Colour range: reddish brown to brownish black; sometimes a mix of both
- Distinguishing feature: The ant's head is heart-shaped compared to the circular heads of most ants.
What should I know about carpenter ants?
To get rid of carpenter ants, it helps to know how they live and behave:
A carpenter ant colony can contain up to 50,000 ants. Colonies are made up of worker ants, brood (larvae and pupae) and the queen, whose main job is to lay eggs and grow the colony.
Typically, the colony or parent nest is located outdoors, and the worker ants come inside to forage for food and water. Worker ants may establish satellite nests indoors, such as within walls, hollow doors and foam insulation panels.
Outdoors, carpenter ants eat honeydew (made from plant sap by aphid, mealybug and scale insects), as well as plant and fruit juices, and bugs. Indoors, they seek out sweets, proteins, and grease.
They will travel up to 300 feet from their nest to find food. They mostly forage dusk through dawn, so this is a good time to inspect for the ants and track their movement. Get tips on how to inspect for ants and how to follow ant trails.
Typically, carpenter ants are active indoors in spring and summer, but central heating may 'awaken' the ants from dormancy in winter.
Where are carpenter ants found indoors?
Carpenter ants prefer wet, water - or fungus-damaged wood, which is soft and easy to excavate. Indoors, this is where water has leaked or is leaking, such as:
- under sinks or bathtubs
- around windows and door frames
- in crawl spaces
- near downspout elbows (even on the second storey)
- under the roof where shingles are missing or damaged
- near a chimney with poor flashing
Signs of indoor carpenter ant activity are:
- unexplained sawdust or wood shavings
- holes or 'windows' that appear in wood
- finding winged ants, or swarmers, which leave the nest to establish new colonies
Where are carpenter ants found outdoors?
Outdoors, carpenter ant nests may be in trees, tree stumps, fence posts, landscaping timbers, firewood, buried wood, piles of wood, brush or leaf litter, and any wood touching soil.
Foraging ants may be active in landscaping plants where aphid, mealybug and scale insects are making honeydew, in garbage and recycling bins, and in garages where food and pet food are stored.
How do carpenter ants get into the house?
Carpenter ants can get indoors through cracks in the foundation, cracks and gaps in caulk, and under doors and windows lacking good seals. They travel along wires and pipes and enter buildings through holes made for these utilities. The ants also enter directly through the tunnels they create in damaged wood. Read our expert guide: How to Keep Ants Out.
What are the best ant killers for carpenter ants?
Carpenter ants are one of the most difficult ants to control. (For tips, read How to Get Rid of Carpenter Ants.) For the best results, use a combination of ant control products:
- Ant repellents – Available as aerosols, foam, fogger, sprays and organic sprays, these products kill ants on contact and are most effective when applied directly to the carpenter ant nest. They also create a defensive barrier that carpenter ants will not cross.
- Ant traps – Ant traps (known as insect bait stations) are filled with an insecticide bait. Foraging ants take bait back to the colony where it is shared among the workers, larvae (baby ants) and queen. Ant traps (also called ant bait stations) are good option if you cannot locate the nest. Ant traps are designed for indoor or outdoor use. Learn more about ant traps and insecticide bait and how to use them.
- Diatomaceous Earth – Often called DE ant powder or DE ant dust, this natural desiccant kills ants by drying them out. It is applied to indoor areas where ants are active. The ants walk through the DE, which scratches the waxy outer layer of their exoskeleton. This causes the ant to dry out and die. DE will not kill the colony, but it will reduce the number of foraging ants. Learn more about DE and how to apply it.
Also read:
How to Get Rid of Carpenter Ants
5 Steps to Get Rid of Ants for Good
