How to Get Rid of Ants Outside: A Canadian Guide for Yards, Patios and Foundations

TL;DR

• Use outdoor ant baits that foraging workers carry back to the queen. Sprays often kill only foragers, and Penn State Extension says they provide partial control.
• You don't need to get rid of every ant. Focus on the nests next to the house, under walkways and in play areas (Health Canada).
• Find the nest by following the ant trail back to where the workers disappear into soil, a crack or wood.
• Put bait stations or stakes right on active trails and near nest openings, out of reach of children and pets. Don't spray insecticide near the baits (Health Canada).
• Keep baits out for at least two weeks. NC State Extension says it may take 7 to 10 days to see fewer ants, and seeing more ants at first is usually a good sign.
• Need help? Get a quote from a recommended local exterminator through Pest Agent's referral form.

The most common mistake people make when working out how to get rid of ants outside is spraying the trail on the patio. The spray kills the foragers in sight, while the queen and the rest of the colony stay safe underground and keep sending out new workers. Outdoor baits work the other way around: workers carry the bait home and share it, which is how the queen gets reached.

A yard with zero ants is not the goal either. Ants in the lawn and the flower beds do little harm and even eat other insects. The colonies worth your effort are the ones along the foundation, under walkways and in play areas, and the real question is what keeps pulling them toward your house instead of the back of the lot.

Why Are There So Many Ants Outside Your House?

Ants outside your house are normal: Canada has many ant species, and most of them nest in soil and come out to look for food during the warmer months. According to the City of Calgary, most species nest outside buildings and enter them only to forage. A few ants on the lawn are not a problem. Busy trails on your patio, along the foundation or into the house are worth dealing with.

Which Ants Live Outside in Canada?

The ants you see outside in Canada are usually one of a few common types:

• Pavement ants: small dark ants that often nest under pavement, patio slabs and foundations. Health Canada notes they can be a nuisance in lawns, gardens and pathways.
• Lawn ants: small brown ants (cornfield and turfgrass ants) that often leave little crater-shaped mounds along driveways, between patio pavers and in bare patches of lawn (NDSU Extension).
• Carpenter ants: large black or black and red ants, 6 to 25 mm long, that often nest in dead trees, stumps and logs (Health Canada). If you see them on the house, read our guide to getting rid of carpenter ants.
• European fire ants: small red-brown ants that can sting, an invasive species in British Columbia. Our guide to red and fire ants covers them in detail.

Food Scraps

Food scraps are the main reason ants gather near your house. Spilled drinks on the deck, barbecue grease, pet food bowls, garbage bins and compost all feed foraging workers. Health Canada advises keeping composters a reasonable distance from the house and emptying and rinsing garbage and recycling containers often.

Aphids on Your Plants

Aphids on your plants attract ants because they produce honeydew, a sweet liquid ants feed on. According to UC IPM, ants protect and care for aphids, soft scales and mealybugs, and outdoor nests are often near plants that carry large numbers of these insects. Ripe fruit left on trees has the same pull. If the ants are mostly in your flower or vegetable beds, our guide to plant-safe ant killers for the garden focuses on treating ants without harming your plants.

Should You Get Rid of Every Ant Outside?

You do not need to get rid of every ant outside, and you could not if you tried. Health Canada says ants should be tolerated as much as possible because they cause little damage in the garden and eat other insects. Penn State Extension adds that ants seldom cause serious damage to home lawns, and Colorado State University notes that totally eliminating ants from a yard is not realistic. Focus on the nests next to the house, under walkways and in play areas. For a broader look at ant species and control, visit our ant guides hub.

How Do You Find the Ant Nests in Your Yard?

Ant nests in your yard are found by following ant trails back to the spot where workers disappear into soil, a crack or wood. Treating the nest, or getting bait to it, is what removes the colony. Killing foragers on the patio does not.

Following Ant Trails

Following ant trails is the easiest way to find a nest. Watch the ants on a warm day: workers carrying food are heading home. Health Canada suggests following trails back to the nest and looking for anthills in the yard, since an anthill shows where the colony has built its nest.

Common Nest Spots

Common nest spots for ants in the yard are easy to check once you know them:

• Cracks in driveways, walkways and sidewalks
• Gaps between patio paver stones
• Bare patches in the lawn where soil is exposed
• Along the foundation and under concrete slabs
• Under stones, boards and landscape timbers

For mounds in the middle of your lawn, our guide on how to get rid of ant hills goes into lawn-specific treatments.

Carpenter Ant Nests Outdoors

Carpenter ant nests outdoors are usually in wood. Health Canada lists dead trunks of standing trees, stumps, logs, and the ground under fallen logs and stones. A carpenter ant nest in a stump next to the house can send workers indoors, so it is worth removing the wood or having the colony treated.

European Fire Ant Nests

European fire ant nests are hard to spot because, unlike most ants, they do not build above-ground ant hills. The Invasive Species Council of BC describes them as red-brown ants about 2 to 3 mm long that can swarm and sting when a nest is disturbed. If you suspect them, do not try to remove the nest yourself and do not move soil, turf or leaf litter off your property. Contact the Invasive Species Council of BC or your local government for advice.

How to Get Rid of Ants Outside

Getting rid of ants outside works best with outdoor ant baits that foraging workers carry back to the queen, backed by targeted nest treatments.

Outdoor Ant Baits

Outdoor ant baits are the most effective way to get rid of ants outside. NDSU Extension calls outdoor baits the best option for outdoor-nesting ants, and UC IPM notes that workers take the bait back to the nest, where the entire colony, including queens, can be killed. The insecticide has to act slowly so the workers survive the trip home (UC IPM). UC IPM adds that prepackaged or refillable bait stations and stakes are the safest and easiest to use. Ants can change what they eat, so give them a choice of a sugar bait and a protein bait, and switch products if they ignore one.

Bait Placement

Bait placement decides whether the bait reaches the colony. Put stations or stakes right on active trails and near nest openings, and use plenty of them. Health Canada notes that two different baits at once may work better. Keep them out of reach of children and pets. Do not spray insecticide near the baits: Health Canada says the bait system will not work if you do. At first you will see more ants around the bait. That is a good sign: they are feeding and carrying it home.

How Long Baits Take

Baits take time. UC IPM says it can take 5 to 10 days to see fewer ants. Health Canada recommends keeping baits available for at least two weeks and expecting to repeat the treatment. Replace baits when they are empty, and move them or try another product if the ants are not taking them.

Boiling Water

Boiling water poured down a nest kills the ants it reaches, but it rarely ends the colony. Health Canada says pouring boiling water and detergent down the nest only temporarily reduces the colony's population.

In tests on fire ant mounds, Oklahoma State University Extension found boiling water did not eliminate all the mounds treated, so surviving nests may need a second treatment. Boiling water also kills grass and plant roots, and carrying it is a burn risk. Use it only on nests in pavement cracks or bare soil, away from children and pets.

Flooding the Nest

Flooding the nest with a garden hose can push a colony away from your house. Health Canada and the City of Calgary both suggest flooding ant nests repeatedly to encourage the ants to move their nest farther from the house. It does not kill the colony, but it is a useful first step for a nest beside the foundation.

Diatomaceous Earth

Diatomaceous earth is a non-chemical powder that dries out ants that walk through it. Health Canada says it is non-toxic to humans and pets, but you should avoid breathing in the dust when applying it. UC IPM warns that dusts stop working once they get wet, and Health Canada says it remains active as long as it is kept dry, so outdoors it mainly helps in dry, sheltered spots such as under a deck or in a dry crack, and may need to be reapplied after rain. Our guide to diatomaceous earth for ants explains how to apply it.

Repellent Sprays

Repellent sprays such as vinegar or essential oils only disrupt ant trails for a short time. NC State Extension notes that spraying only serves to repel ants, and they will likely return. Use them, if at all, to wipe a trail on a patio door.

Homemade Borax Bait

Homemade borax bait is a common online tip, but Health Canada advises against it. Its guidance says "Do not make homemade pesticides using boric acid," and borax can produce boric acid. In Canada, domestic boric acid products are now generally sold as sealed bait stations or localized gels, and Health Canada says to place bait stations out of the reach of children and pets. Buy a registered bait station instead of mixing your own.

When to Call a Pest Control Professional

Calling a pest control professional makes sense when carpenter ants are nesting in wood near or in the house, when you suspect European fire ants, or when ants keep coming back after several weeks of baiting. Health Canada recommends a professional exterminator for difficult carpenter ant situations. UC IPM advises asking any company you hire to use baits and spot treatments rather than perimeter treatments or monthly sprays. If you need help, you can get a quote from a recommended local exterminator through Pest Agent's referral form.

What Is the Best Outdoor Ant Killer?

The best outdoor ant killer for most yards is a ready-to-use outdoor bait station or stake, because it reaches the colony and keeps the insecticide contained. Other products have a place, but each comes with trade-offs. For tested picks, see our best ant killer roundup.

Bait Stakes

Bait stakes are plastic stations filled with liquid bait that you push into the soil near trails and nests. According to NDSU Extension, many liquid outdoor baits contain boric acid (borax), which acts as a stomach poison, and UC IPM notes some borate products are registered for home use. Check the label for the ants it covers: some liquid borax stakes target sweet-eating ants such as pavement ants and are not meant for carpenter or fire ants.

Granular Baits

Granular baits are scattered over a larger area, along trails or around nests. NDSU Extension notes that they treat larger areas but cost more, and that they should not be watered in, because water breaks the bait down faster.

Nest Foams

Nest foams are aerosol insecticides sprayed into an anthill or a crack to reach the ants inside. Health Canada notes that applying a chemical directly on the nest may eliminate the colony. They only work if you have found the nest, and they kill the ants they touch, so pair them with baits for colonies you cannot reach.

Perimeter Sprays

Perimeter sprays are a last resort, not a first step. UC IPM warns against spraying pyrethroids such as bifenthrin and cypermethrin outdoors, especially on driveways, sidewalks and around foundations, because they pollute waterways. Perimeter treatments also carry more risk to the environment than baits in stations, and sprays kill foragers rather than the colony. The City of Calgary adds that chemical barrier spraying may cause a colony to split. NDSU Extension suggests broad-spectrum granules or lawn sprays only as a last resort because they also kill beneficial insects.

The PCP Number

The PCP number on an outdoor ant killer shows that Health Canada has registered the product under the Pest Control Products Act. Always look for it on the label, read the directions and follow them. The City of Calgary also reminds you to check that the product is labelled for outdoor use.

Provincial Pesticide Rules

Provincial pesticide rules can limit which outdoor ant killers you may use. Health Canada notes that some provinces and municipalities restrict certain lawn and garden pesticides, so check with your city, province or a local lawn care centre. Ontario, for example, bans the cosmetic use of pesticides: unless an exception applies, only low-risk products on the province's Allowable List may be used on lawns, gardens, driveways and around the home, and Health Canada says to use only a registered pesticide according to the label directions.

Pet and Child Safety

Pet and child safety comes down to placement and timing. Put bait stations where children and pets cannot reach them, and keep kids off treated grass until the product has been watered in and the grass has dried, as Penn State Extension advises. If you have a dog or cat that roams the yard, our guide to pet-safe ant killers compares lower-risk options.

How Do You Keep Ants Outside From Coming Back?

Keeping ants outside from coming back means removing their food, their nesting spots and the bridges that lead into your house. UC IPM notes that treatments in late winter and early spring, when colonies are just starting to grow, work best, so start before the summer peak.

Foundation Clearance

Foundation clearance is the easiest change to make. UC IPM recommends keeping plants, grass and mulch at least a foot (about 30 cm) away from the foundation to reduce ant foraging and nesting. Trim shrubs and branches that touch the house, since ants use them as bridges.

Sealing Cracks

Sealing cracks stops outdoor ants from foraging inside. Health Canada advises repairing and sealing as many visible cracks in the foundation and exterior walls as you can. Caulk gaps around door thresholds, windows and the spots where pipes and wires enter. If ants are already inside, our guide on how to get rid of ants in the house covers indoor steps.

Lawn Care

Lawn care makes your yard less inviting to nesting ants. NDSU Extension recommends watering regularly and mowing at a height of three to four inches (about 7.5 to 10 cm) to encourage thick grass, which can discourage ant nesting. Reseed bare patches, since lawn ants often nest where soil is exposed.

Firewood

Firewood stacked against the house is an open invitation to carpenter ants. Health Canada advises keeping firewood away from the sides of buildings, not burying stumps or wood debris close to the house, and clearing away decaying wood.

Sticky Barriers

Sticky barriers keep ants out of trees and off plant stands. The City of Calgary notes that ants will not cross sticky barriers and suggests two-sided tape around plant stands and fruit trees. UC IPM recommends banding tree trunks with a sticky product, which can help keep ants away from aphids.

Garbage Bins

Garbage bins and compost draw ants close to your door. Rinse bins often, keep lids closed, and place composters a reasonable distance from the house, as Health Canada advises.