Why Ants Invade Ontario Homes in Spring and How to Get Rid of Them

Every spring across Ontario, homeowners start noticing ants marching across kitchen counters, appearing in bathrooms, or emerging from walls. It happens every year and it always feels sudden, but the colony responsible has often been building for months before you see a single ant.

Why Spring Triggers Ant Activity

Most Ontario ant species are dormant or semi-dormant through winter. As soil temperatures rise above 10°C in April and May, colonies become active again. Workers fan out in search of food and water. This is also when winged reproductive ants, known as swarmers, emerge to start new colonies, which is why you might suddenly see what looks like flying ants indoors in spring.

The Three Most Common Ants in Ontario Homes

Carpenter ants are Ontario's largest ant species black, up to 25mm and are the most damaging. They do not eat wood but excavate it to build galleries for nesting, weakening structural elements over time. Finding large black ants indoors in spring, especially near wood and moisture, is a serious warning sign.

Pavement ants are small dark brown ants that nest under slabs, foundations, and driveways. They trail into homes along walls looking for greasy and sweet foods. They are far less destructive than carpenter ants but can be very difficult to eliminate without professional treatment.

Pharaoh ants are tiny yellowish ants that thrive in heated buildings year-round. They are particularly problematic in apartment buildings and hospitals. Critically, spraying pharaoh ants causes them to split into multiple new colonies, making the problem significantly worse.

Why Store-Bought Ant Spray Rarely Works

Surface sprays kill foraging workers but have no effect on the colony, which may contain hundreds of thousands of workers and multiple queens deep inside a wall void or under your foundation. Within days of spraying, new workers fill the same trails. For carpenter ants and pharaoh ants in particular, professional treatment is the only reliable solution.

What Professional Ant Treatment Involves

For carpenter ants, treatment starts with identifying the nest location often in moist or decaying wood near the exterior and applying targeted professional-grade products that reach the colony. Pavement ant treatment uses gel baits and perimeter treatment that foraging workers carry back to eliminate queens. Pharaoh ants require a specialist slow-acting bait protocol never spraying.

Preventing Ants From Coming Back

• Fix moisture problems leaking pipes, poor drainage, and wood-soil contact attract carpenter ants
• Seal cracks in the foundation and gaps around pipes
• Keep firewood away from the house
• Trim tree branches that touch the structure
• Store food in sealed containers

XtermaPro Pest Control treats all ant species across Toronto, Peterborough, Markham, and surrounding areas. We identify the species before treating because the right approach for carpenter ants is completely different from the right approach for pharaoh ants, and getting it wrong makes things worse.