How to Get Rid Of Ants In A Lawn

Last Updated on May 16, 2026 by Duncan

A few summers ago I walked out to mow my lawn and counted eleven ant mounds in a 20-foot stretch of grass. The ants had been there for weeks and I had been ignoring them, assuming they would move on.

They did not move on. They recruited friends. By the time I dealt with the problem I had dead patches of grass the size of dinner plates and a mower that kept bogging down in the disturbed soil.

If you are reading this article, you are probably at an earlier stage than I was, which is good news because the earlier you act, the easier this is to fix.

This guide covers every practical method for getting rid of ants in a lawn, from the gentlest DIY approaches to the nuclear options, with honest notes on what works fast and what requires patience.

How Ants Actually Damage Your Lawn

Ants are not purely villains. They aerate soil by digging tunnels that carry oxygen and water to grass roots, and they accelerate the decomposition of organic matter like dead leaves and insects. A small, stable ant population is genuinely helpful to lawn health.

The problem is that ants are social insects and colonies grow exponentially. A single queen can lay hundreds of eggs per day, so a manageable handful of ants in spring can become a serious infestation by midsummer.

Once a colony gets large enough, the damage becomes visible. Ant colonies build dense tunnel networks through grass root systems, and those tunnels physically sever roots, which is why you get dead brown patches in the shape of a colony’s footprint.

The mounds of excavated soil that appear above ground kill the grass underneath by blocking sunlight and smothering the blades. On a short lawn, a single large mound can kill a patch of grass two feet across.

Beyond the lawn itself, large mounds are a tripping hazard for children and pets and cause real problems when mowing. Mower blades that hit compacted soil mounds quickly dull, and the uneven surface makes it nearly impossible to get a consistent cut height.

Fire ants and European red ants add another dimension to the problem: they will sting. If you have either of these species on your lawn, treat the infestation as urgent rather than cosmetic.

5 Proven Methods for Getting Rid of Ants in a Lawn

1. Soapy Water

Dish soap dissolves the waxy protective coating on an ant’s exoskeleton, which causes them to dehydrate and die on contact.

It is the most accessible method since almost every household has dish soap, and it causes no lasting harm to your lawn if you use it at the right concentration.

Fill a spray bottle with one part dish soap and two parts water. Shake it thoroughly to combine. Spray the mixture directly onto active ant mounds and any visible trails.

For the mound itself, pour a generous amount of the soapy solution directly into the entrance tunnels to reach the colony below the surface.

Some recipes call for adding baking soda, cider vinegar, or peppermint oil. In my experience the plain dish soap solution works just as well and is cheaper. The peppermint oil version does have the advantage of acting as a mild repellent afterward.

Boiling water is a more aggressive variation of this approach. Carry a full kettle of boiling water to the mound and pour it slowly into the entrances.

Boiling water will kill ants on contact, including the queen if you manage to flood the right tunnel, but it will also scald your grass.

Use it only on mounds in bare patches or on a lawn you are prepared to reseed. Wait several days after treatment and repeat if you see new ant activity.

If you are dealing with fire ants or European red ants, wear closed-toe shoes, long pants, and long sleeves before getting close to the mound. These species are quick to swarm when disturbed.

2. Boric Acid

Boric acid is a slow-acting poison that affects ants through three pathways: it damages their nervous system, corrodes the lining of their stomach when ingested, and degrades their exoskeleton on contact.

The key word is slow. This method takes weeks, sometimes months, before you see complete colony elimination.

The reason it works so well despite being slow is that ants carry the boric acid back to the nest. You are not just killing the foragers you can see; you are poisoning the source.

You can buy boric acid online or from most pharmacies. To make an effective bait, mix three quarters of a teaspoon of boric acid with a food that foraging ants in your area find attractive.

Common choices are sugar water, honey, peanut butter, bacon grease, or jelly. The food type matters because different ant species prefer different food sources.

If you are not sure what species you have, try two baits side by side: one sweet (honey) and one fatty (peanut butter). See which one the ants prefer, then make a larger batch of that one.

Place the bait as close to the mound entrance as possible and leave it undisturbed for several days. Resist the temptation to spray anything else on the mound while using boric acid bait, since you do not want to repel the foragers before they collect the bait.

The amount of boric acid needed to kill ants is small enough that accidental contact or ingestion by children or pets is not a serious hazard. That said, store unused boric acid out of reach and away from food.

3. Diatomaceous Earth

Diatomaceous earth is fossilized algae ground into a fine powder.

It kills ants mechanically rather than chemically: the microscopic sharp edges of the particles cut through the waxy outer layer of an ant’s exoskeleton, and the powder then absorbs the moisture and oils from the insect’s body.

The ant dehydrates and dies. The process typically takes 16 hours for red ants and up to 24 hours for larger black ants.

You can buy diatomaceous earth online or from garden centers. When purchasing, read the label carefully. You want food-grade diatomaceous earth intended for pest control. Pool-grade diatomaceous earth is chemically treated and is hazardous to breathe.

Apply it by sprinkling a thin layer along ant trails and around the base of mounds. You can also pour some directly into the mound entrance. Wear gloves and a dust mask when applying because the powder is harmless to your lungs in trace amounts but irritating in larger quantities.

The critical limitation of diatomaceous earth is that it only works when it is dry. Rain, dew, or irrigation will render it ineffective.

Apply it on a dry day when no rain is forecast for at least 48 hours. If it gets wet, let it dry out completely and it will partially regain effectiveness, but freshly applied dry powder works significantly better.

In my experience this method works well on smaller colonies and as a preventative barrier around the edges of a lawn. For large, established colonies, it is better used in combination with another method.

4. Ant Killer Sachets

If you need results within 24 to 48 hours rather than days or weeks, ant killer sachets are the most reliable option for a lawn.

The active ingredients in commercial ant killers are absorbed through the nest and kill the entire colony including the queen, not just the surface workers.

One of the most consistent products I have used is Nippon Ant Killer from Vitax. Dilute one sachet into five liters of water, then apply it over the affected area using a watering can or a knapsack sprayer. Use enough volume to penetrate deep into the nest rather than just wetting the surface.

For large nests you may need a second application three to four days after the first. Watch the mound after treatment: if you see no ant activity within 48 hours, the colony is likely dead. Continued activity after 72 hours means you should apply a second round.

This approach works on most common lawn ant species and does not require you to locate the exact nest entrance since the diluted solution soaks into the surrounding soil.

5. Ant Bait Stations

Bait stations work on the same principle as boric acid bait but come pre-filled and ready to place. The station contains a slow-acting liquid attractant that foraging ants drink from and carry back to the nest.

As more ants bring the active ingredient into the colony, it gradually spreads through the population and eliminates it from the inside out.

The Terro Ant Bait Station is one of the most widely used options and works well against sweet-eating ant species, which are responsible for the majority of lawn infestations.

Place the stations as close to the mound or ant trail as possible without disturbing the ants around them.

Do not use ant bait stations alongside sprays or repellents. The two approaches contradict each other. Sprays kill foragers before they can carry bait back to the nest.

Expect to wait one to two weeks for a significant reduction in activity. The delay is by design: if the bait killed ants too quickly, foragers would avoid it. The slow action is what allows it to reach the queen.

Which Method Should You Use?

The right method depends on urgency, the size of the infestation, and how much lawn damage you are willing to risk.

For small, new mounds with limited ant activity, start with soapy water or diatomaceous earth. Both are inexpensive and cause no harm to your grass when used correctly. If you see no improvement after five days, escalate.

For moderate infestations where you have multiple mounds but no dead grass patches yet, boric acid bait or a bait station is the most thorough option because it targets the queen rather than just the workers. Accept that it will take time.

For large infestations with visible dead patches, or for fire ant or European red ant colonies, go straight to ant killer sachets.

The speed and penetration depth of a diluted sachet treatment gives you the best chance of eliminating the colony in a single application.

When to Call a Professional Exterminator

If you have tried two or more methods over the course of three weeks and the colony is still active, it is time to bring in a professional.

Some ant species build extremely deep or branching colony networks that consumer products cannot reach.

A licensed exterminator has access to commercial-grade treatments and the expertise to identify the species and target the nest architecture specifically.

Many pest control companies offer a warranty on ant treatments, meaning they will return to re-treat at no additional cost if the colony reestablishes within a set period, typically 30 to 90 days.

Ask about this before booking, because a guarantee is a good sign that the company is confident in their method.

The professional route is also worth considering if the infestation covers a large area of lawn, involves fire ants near where children or pets play, or if the ants have begun entering your home from the lawn.

Preventing Ants From Coming Back

Once you have dealt with an infestation, a few habits make it far less likely that a new colony will establish itself.

Keep your grass at the recommended mowing height for your species (longer grass shades the soil surface, which ants find less hospitable for nesting).

Fix any areas of compacted or poorly draining soil since ants prefer dry, loose earth. Remove dead wood, leaf piles, and any organic debris near the lawn perimeter because these are common nesting starting points.

A light perimeter application of diatomaceous earth along fence lines and garden borders at the start of spring acts as a useful deterrent, particularly if you have had recurring infestations in the same area.

You can also read our guide on how to regrow damaged grass if ant activity has already left bare patches that need attention.

Final Word

Ants in a lawn are a manageable problem when you catch them early and match the treatment to the scale of the infestation.

Soapy water handles small outbreaks. Boric acid and bait stations eliminate entire colonies over time. Ant killer sachets give you fast results when patience is not an option. And a professional exterminator is there for the situations where nothing else has worked.

The worst thing you can do is wait. A colony that is easy to treat in May will be a significant lawn restoration project by August.