In Duluth, ant season is short but intense. Once the snow leaves the hillsides and the wood around foundations starts to warm, colonies that spent the winter in dormancy get going, and by late spring many homeowners are seeing trails in the kitchen. The thick forests around the city and the many older wood houses make the area particularly good habitat for one of the most destructive ants in the country, the carpenter ant.
Carpenter ants first
Black carpenter ants, often with a reddish thorax, are large, up to half an inch for the workers. They nest in moist or decaying wood such as stumps, fence posts, rotted window sills, porch posts and wet wall cavities. They do not eat the wood; they chew galleries and push out coarse shavings called frass. Finding a few big black ants wandering the kitchen at night in spring is a classic warning that a colony is nearby, often inside the home itself.
The smaller kitchen invaders
Odorous house ants are small, dark brown and give off a rotten-coconut smell when crushed. They love sweets and nest in wall voids, under mulch and in cracks along the foundation. Pavement ants, which build nests under sidewalks, patios and slab edges, come indoors through basement cracks. Both can arrive in large numbers after heavy rain or when the weather turns suddenly dry.
Duluth conditions that feed them
- Heavy tree cover in neighborhoods like Woodland, Hunters Park and Chester Park, with branches that touch roofs and siding.
- Moist soil on the uphill side of hillside homes during snowmelt.
- Old window sills, porch columns and decks where water collects and wood softens.
- Stacked firewood against exterior walls, a favorite carpenter ant nesting spot.
- Lake humidity along the shore, from Canal Park through Park Point.
What an ant pro does
The first task is species identification, because the treatment differs. For carpenter ants, the goal is to find the parent colony and any satellite nests, which may be in wet wood in a bathroom wall or around a chimney. Moisture sources are corrected, and treatment uses dust, residual spray or bait placed where ants travel. For odorous house and pavement ants, bait stations are placed along trails so workers carry product back to the queens, and a perimeter treatment limits new scouts. Spraying visible ants alone usually just causes the colony to spread.
Prevention suited to the North Shore
- Replace rotted trim and fix leaking gutters, flashing and roof valleys.
- Cut back tree limbs and vines that bridge to the house.
- Move firewood and wood scraps away from the foundation.
- Keep sweet spills and pet food cleaned up, and store honey and syrup in sealed jars.
- Seal gaps where pipes and cables enter the basement.
Who to call
PestMinistry is a referral service, not a pest control company. Call (844) 725-1661 and we will connect you with an independent licensed provider in our network who serves Duluth and can sort out which ant you have.
Are carpenter ants a sign my house is rotting?
They are often a sign of moisture damage somewhere. They prefer wood that is already damp, so fixing the leak is part of the cure.
Do ants die in the winter?
Outdoor colonies go dormant, but a colony nesting in a heated wall can stay active, so winter sightings indoors deserve attention.
Are fire ants a problem in Duluth?
No. Fire ants are a southern pest and do not survive Minnesota winters, so stinging mounds here point to another species.