Fighting fire ants

By Heather Kirk-Ballard

LSU AgCenter Horticulturist

Fire ants are formidable pests in gardens and landscapes. They’re known for their painful bites and stings due to venom. When disturbed, fire ant mounds can unleash swarms of sterile female worker ants that sting and inject venom within seconds, potentially causing severe allergic reactions or dangerous medical issues in some individuals.

Fire ant colonies, which can contain up to 200,000 ants, consist mainly of female workers and a queen capable of laying up to 1,600 eggs daily. These colonies create extensive underground tunnels and can take months to grow visible mounds.

Originally introduced to the U.S. via South American cargo ships, fire ants have spread extensively in warmer southern and southeastern regions thanks to their resilience. Their diet includes pests like flea larvae and cockroach eggs, but they're also drawn to electrical equipment, posing a dilemma for control efforts.

As the weather warms in the spring and the ground begins to dry, mounds are more evident when they emerge from their dormancy and begin their tyranny. There are a variety of products and methods at your disposal to help control their population and rid your landscape of nuisance ant mounds. Always read labels carefully before purchasing products and make sure you understand the directions before using them.

Be aware that ant baits can pose a risk to birds. Organophosphate and carbamate insecticides can cause respiratory failure and death in birds. Some safer alternatives are insect growth regulators (IGRs) that interfere with egg development, preventing immature stages from reaching adulthood. Methoprene used in ant baits is much safer for our feathered friends.

Diatomaceous earth, an organic, nontoxic powder, can be used as a perimeter treatment to control ants. Other organic options include insecticides with boric acid, pyrethrin or rotenone labeled for ant control. Boiling hot water can be used but hardly ever penetrates the entire mound. A second application in the following days will be needed to eliminate the remainder of the mound.

There are other chemical controls you can use; however, they can be toxic to birds and other small mammals. Retired AgCenter entomology specialist Dale Pollet recommends using baits. They should go out starting now in April and again in October for best control. He says it is crucial to apply baits when a couple days of dry weather is expected so they don’t wash away.

Baits are safe for use around pets, but if you have chickens, he recommends putting the birds up for a few days when applying. Never apply baits near water systems such as ponds and lakes.

Baits consist of an insecticide combined with a food material that the fire ants will eat. They then bring the bait back to the colony and feed it to other ants, including the queen. Mounds can be treated individually, but it is best to broadcast it over an entire yard at a rate of 1 to 2 pounds per acre.

For small lots, a 1/2-to-3/4-pound application is sufficient to treat the entire yard. Want to be even more effective? Coordinate with your neighbors or work with your homeowners’ association. Treating your yard along with surrounding ones will offer the best control.

Some additional options are dusts that typically contain acephate. Apply the dust to the mound and it will pass through the entire colony, killing them within days.

Mound drenches are liquid concentrates mixed with water to create 1 gallon of diluted mixture. Apply to the top of the mound when the ground is dry, and ants should die within a day. If the ground is already saturated with water, you will not get movement of the insecticide to penetrate underground to the entire nest.

Granules are another method, usually used to treat mounds by sprinkling the recommended amount on the top of the mound without disturbing it. Make sure to completely penetrate the mound, or ants will move to a different site through underground foraging tunnels to avoid the insecticide.

Now, let’s dispel some myths. Grits do not work to kill ants. In fact, you will just be feeding them because, much like us Southerners, ants love them! Also, a shovel from one mound on top of another to make ant colonies fight a gauntlet to the death is an exciting notion (imagine tiny ants in gladiator suits), but again, there is no merit to this myth. In fact, colonies can spread up to 25 feet. Different mounds are probably part of the same colony, so avoid the colony reunion and save your back.

You can consult the LSU AgCenter’s free publications, including the “Louisiana Home Lawn Series: Red Imported Fire Ant” and “Managing Imported Fire Ants in Urban Areas,” for additional guidance. Search for these titles at

fire ants

Fire ants can bite and sting. Venom causes the stinging pain. Photo by Claudia Hussender/LSU AgCenter

4/5/2024 2:42:17 PM
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