Carpenter Ants
Carpenter ants, sometimes referred to as “termites of the northwest,” can be important structural pests which typically nest in moisture-damaged wood. In our region, swarms of flying reproductives (males and females) often leave the nest during January. After mating, the surviving queens will shed their wings and search for a new nest site.
Once a thriving colony is established, it has 10,000 to 50,000 or more individuals. The main nest is in dead wood, perhaps a tree, stump, or landscape timbers.
But that’s only part of the story.
The pupae and some workers are in a secondary nest, one that’s in a relatively warm, dry structure such as a house, garage, or shed. When a colony is about 6 to 10 years old, it produces its first winged swarmers (reproductive males and females). The females, at 16- to 18-mm (about 5/8-inch), are larger than the males, the latter a scant 1/2-inch long.
Key Facts…
Secondary nests in structures begin in moisture-damaged wood.
Buildings near a wooded area are more liable to attack than others.
Carpenter ants don’t eat wood; instead, they excavate wood for housing.
Carpenter ants feed on honeydew and captured insects.
If winged ants emerge indoors from underneath the baseboard, the nest is probably in the wall; if via a ceiling light fixture, in the space above, in either the attic or ceiling void.
Locating the Main Nest
Look for piles of fresh sawdust in the attic and crawl space.
To determine where the ants are entering the structure, look for 2-way trails outdoors. The best time to look for trailing ants is from 10 PM to 2 AM during April through October. Inspect along the foundation and other architectural lines, in the crawl space, and where utilities (pipes and wiring) enter the structure.
If a trail is found follow it to the main nest. In order to limit structural re-infestations, the main nest must be treated by a pest control company.
Prevention
Create an airy clear zone by trimming, or removing, any plant material within 12 to 18 inches of a structure.
Maintain a minimum gap of 8 inches between mulch and siding.
Ensure roofing is intact.
Inspect the perimeter of the structure periodically, to check for a 2-way trail which warns of an infestation.
Management Practices
Correct any moisture problem(s) and replace damaged wood
Hire a pest control company to treat the structure and, whenever possible, the main nest.
NOTE: Over-the-counter ant baits available in the northwest are ineffective against carpenter ants.