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Structural Pests: Carpenter Ants, Much More than Just a Nuisance
Posted By: Daniel Mackie

Structural Pests - Carpenter Ants, Much More than Just a Nuisance in the Greater Toronto Area


Ants have long been a significant urban pest, but they only recently have emerged as structural pests that cause vast structural and other damage. Carpenter ants, in particular, have been recognized as important North American structural pests, in some areas causing damage that’s considered equal to or more serious than that caused by termites.


Wood, Their All-Time Favorite


Carpenter ants build their nest in wood structures or other wood products, seeking out moist wood that contains decay fungi, but also settling for dry, healthy wood. One of the many things that make them a feared enemy is that their nests can be found almost ANYWHERE inside a building structure, including:


  • Outside the house: porch pillars, window frames and sills, roofs, siding, girders, support timbers, shingles, joists, studs, casings of houses and annexes, etc.


  • Inside the house: inside chest and cabinet drawers, stored cardboard boxes, behind books in libraries, under floors, under bathtubs and showers, in hollow doors, in attic spaces, ceiling voids, hollow ceiling beams, below bay windows, in false ceilings, around skylights, etc.


Carpenter ants also infest non-wood materials. Inside the house, they create their nests inside insulation used in attics, walls, subfloors, or ceilings, as well as foam, drywall, and particleboard. One favorite nesting site is hot tubs, which offer the best of both worlds – wood exterior and foam or fiberglass insulation – on top of providing the warmth and moisture they need for survival and growth.  Besides structures, carpenter ants are significant pests of standing timber, with white cedar, balsam fir, and red and white spruce among their favorites.


Unlike termites or other wood-infesting insects, carpenter ants do not eat the wood they nest in. They excavate tunnels into the wood against the grain and then remove the sawdust to another location, away from the wood tunnels. This ritual of eliminating the wood chips from the entry makes it far more difficult for homeowners to locate their nest, as all that remains visible is a small oval hole inside the wood. The process of building their nest is lengthy, and their damage is done slowly, but that doesn’t make it less significant.


Ontario Canada Carpenter Ant Removal and Control


Carpenter ant infestations are usually a sign that there is a moisture problem inside the building. Often, infestations begin because of a water leak around the gutter, window, chimney, or door frame. Kitchens, laundry areas, and bathrooms invite ants, especially if there’s a leak in a water pipe or heating system that provides ants the moisture they so much love.


How to Tell If You Have a Carpenter Ant Problem inside Your House


Telling if it’s indeed carpenter ants you’re seeing in and around your house can be quite difficult, for several reasons. First of all, there are about 100 species of ants found in Canada, so narrowing down which ones are trailing along your window sill may be more challenging than you think. Secondly, they are nocturnal creatures, doing most of their foraging at night, so you probably will not see them in broad daylight unless they are under stress due to lack of food or water or because they are reproducing. Third, they sometimes build their nests in parts of a building that aren’t visible or have low traffic, causing extensive damage to a structure well before they are detected.


There are, however, certain signs that can help you recognize if you have carpenter ant damage, including:


  • The presence of frass (extruded sawdust, bits of soil, parts of insects, and dead ants) outside of nest openings
  • Small windows cut into infested wood that act as garbage chutes used for the disposal of frass and other unwanted materials
  • The presence of swarmers (winged reproductives) or their wings on window ledges, in light fixtures, or in spider webs during spring
  • Rustling noises in walls or ceilings
  • Foraging trails (ants will habitually use the same routes to travel to and from the nest to food and water sources)


If you’re lucky, one or more of these signs can help you diagnose your ant problem and, hopefully, locate the nest, but that’s almost never the end of your troubles.


Carpenter Ants Prevention Toronto


A carpenter ant colony is often formed of a series of nests, with the main nest (parent nest containing the queen) located outdoors, and several sub-nests (satellite nests) formed inside the structure.  Most of the times, it is satellite nests that are encountered inside structures, and eliminating them will only provide short-term relief. To completely eliminate carpenter ants from a property, the parent nest(s) and the satellite nests must all be localized and eliminated, otherwise the ants will reappear in a few days or weeks.


When a carpenter ant infestation is suspected, it’s always best to resort to the specialized help of a pest control professional, especially when dealing with a large colony or if the nests are hard to detect. A skilled pest management professional will be able to not only use effective control methods to pinpoint and eliminate all nests, but also treat the exterior perimeter of your house to eliminate moisture problems and protect it from future carpenter ant foraging.


About the Author

Daniel Mackie, co-owner of Greenleaf Pest Control, is a Toronto pest control expert well-known as an industry go-to guy, an innovator of safe, effective pest control solutions, and is a regular guest on HGTV. Mackie, along with business partner Sandy Costa, were the first pest control professionals in Canada to use detection dogs and thermal remediation for the successful eradication of bed bugs. In his free time, he is an avid gardener.

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