Ant Prevention Guide for London Ontario Homeowners

Ant calls are highest from late April through July in London Ontario. The good news: most ant problems caught early are manageable. The ones that get out of hand are almost always ones where the wrong approach was used for weeks before professional help was called.

The Ant Species You're Likely Dealing With

Pavement Ants

The most common ant in London Ontario homes. Small (2–3 mm), dark brown to black. Their colonies establish under concrete — driveways, patios, sidewalk edges, and foundation slabs. They enter homes through expansion joints, gaps around utility penetrations, and cracks in the foundation. You'll typically see trails along baseboards, in kitchens, and near exterior doors.

Good news: Pavement ants respond well to exterior perimeter bait programs. Act in spring before the colony fully mobilizes.

Where to look: Along the edge of your concrete driveway or walkway, you'll often see fine soil pushed up between slabs — that's the colony displacing material as it expands.

Carpenter Ants

The one ant species you should never leave untreated. Carpenter ants (6–13 mm, typically black) don't eat wood — they excavate it to build galleries. Satellite colonies establish in structural wood that has existing moisture damage: window frames, door frames, areas near roof penetrations, and wood in contact with soil.

The evidence for carpenter ants is frass — coarse, sawdust-like material pushed out of galleries. It looks like someone shaved wood near the wall. If you find frass, the colony is actively expanding.

In Byron and Wortley Village, carpenter ant calls are common in older homes with wood-framed windows and soffit areas that have experienced water intrusion. The moisture damage creates the soft wood that carpenter ants prefer.

Odorous House Ants

Small, dark, and they smell distinctly like rotten coconut when crushed. They're opportunistic nesters — colonies establish in wall voids, under flooring, and around electrical boxes. These ants are difficult to control with consumer sprays because colony fragmentation (called "budding") creates new satellite colonies when the main colony is stressed.

Pharaoh Ants

Tiny (1–2 mm), yellow-orange, with a preference for warm multi-unit buildings. Common in apartment buildings in central and south London. Pharaoh ants are notoriously resistant to spray-based treatments — budding produces multiple new colonies for every one disrupted. Gel bait programs targeting forager trails is the only reliable approach.

Entry Points: Where Ants Get In

Identifying and addressing entry points is as important as treating the colony. Common routes:

• Gaps around utility penetrations (pipes, conduit, cable) where they enter through the foundation or exterior walls
• Expansion joints in concrete — especially around garage floors and driveways
• Door thresholds and window frames with degraded weatherstripping or caulking
• Vegetation touching the building — shrubs, tree branches, and groundcover act as highways

A perimeter inspection in early spring, with caulk and weatherstripping addressed before ants mobilize, removes the easiest entry routes.

Seasonal Timing: When to Act

Late March to April: Ant queens emerge and begin establishing new colonies. Perimeter bait applied now works against a small population, not a large one. This is the best window for preventive treatment.

May to June: Peak forager activity. If you're seeing trails indoors, the colony is established. Bait programs work but take longer.

July to August: Large, well-established colonies. DIY results are less reliable at this stage because the colony can lose significant numbers and recover. Professional treatment makes more sense.

Fall: Colonies overwinter in deep soil or wood. A fall perimeter treatment with non-repellent bait reduces the overwintering population that will re-emerge next spring.

DIY vs Professional: When to Switch

DIY is reasonable when:

• You have pavement ants and a small, recent trail
• You've found and sealed the entry point
• You're using gel bait (not spray) from the hardware store

Call a professional when:

• You're dealing with carpenter ants (structural damage risk)
• You've sprayed and the problem returned within a week
• You're in a multi-unit building with pharaoh or odorous house ants
• You've used two or more products over two or more weeks without improvement
• You can't locate the nest or entry point

The most common mistake: using repellent sprays on forager trails. This breaks the trail temporarily but doesn't reach the queen. The colony re-routes and re-establishes, sometimes with more than one trail where there was previously one.

Read more about our ant control service, or book an inspection if you're past the point where DIY makes sense.