The presence of aggressive, stinging “red ants” often signifies an infestation by the Red Imported Fire Ant, Solenopsis invicta. This invasive species, native to South America, is known for its painful venom and the large, dome-shaped mounds it constructs. Fire ant colonies pose a threat to people, pets, and local ecosystems, requiring a systematic approach for successful management. Homeowners need effective strategies to eliminate existing colonies and prevent future re-infestations.
Identifying the Threat and Immediate Safety Precautions
Properly identifying the pest is the first step toward effective control. Fire ant mounds are typically dome-shaped piles of loose soil, often found in sunny areas, and they lack a central entrance hole at the peak. The worker ants are reddish-brown with a darker abdomen, varying in size from approximately \(1/16\) to \(1/4\) inch within the same colony.
If a mound is disturbed, hundreds of workers will emerge rapidly, stinging repeatedly and almost simultaneously. A fire ant sting causes an immediate burning sensation, followed within 24 hours by the formation of a distinctive white, fluid-filled pustule at the site. If stung, move away quickly to avoid additional attacks, then apply a cold compress to the affected area.
Do not scratch or break the resulting pustules, as this can lead to secondary bacterial infection and scarring. Watch for signs of a severe allergic reaction, such as difficulty breathing, swelling of the tongue or throat, or dizziness, and seek emergency medical attention immediately.
Methods for Targeted Mound Elimination
Targeted mound treatments are designed for the immediate destruction of visible, active colonies. These methods involve applying a product directly to the mound, aiming to kill the queen deep within the subterranean network. Success depends on not disturbing the nest beforehand, which causes the colony to scatter or move the queen.
The liquid drench method involves pouring a large volume of liquid insecticide, mixed according to label instructions, directly onto the mound. This quickly saturates the nest, killing ants on contact and providing a higher chance of reaching the queen. This treatment is most effective when ants are nesting near the surface, typically during mild temperatures in the morning or evening. However, drenching requires significant amounts of water and insecticide, making it labor-intensive and potentially less environmentally sound.
Another option uses pesticidal dusts or granules applied over the mound, relying on the ants to carry the poison below the surface. Products containing active ingredients like acephate are commonly used for this method, which is convenient and requires less labor than a drench. Dry treatments are generally slower acting, sometimes taking a few days to eliminate the colony entirely.
For a non-chemical approach, slowly drenching the mound with two to three gallons of almost boiling water (190°F to 212°F) can be attempted. This method has a success rate that varies widely (20 to 60 percent), due to the difficulty of ensuring the water penetrates deep enough to kill the queen. A significant drawback is the extreme hazard of handling large volumes of boiling water, and it will kill any vegetation the water contacts.
Achieving Long-Term Control and Prevention
Achieving lasting control requires shifting from a reactive strategy of killing visible mounds to a proactive, area-wide management program. The most effective long-term solution is a baiting program, which targets the entire colony structure, including the queen. Fire ant baits consist of an attractive food substance, usually corn grits coated with soybean oil, mixed with a slow-acting insecticide or insect growth regulator.
Worker ants forage for the bait and carry it back to the nest, where they feed it to the queen and developing larvae, allowing the poison to spread throughout the colony. Baits containing ingredients like hydramethylnon or methoprene are slow-acting, often taking several weeks to months to achieve maximum control. Baits must be applied when ants are actively foraging, avoiding wet conditions, rain, or the extreme heat of midday, as moisture and high temperatures reduce the bait’s appeal.
The “Two-Step Method” is a highly recommended integrated approach that combines broadcast baiting with targeted mound treatments. This involves broadcasting the bait over the entire yard once or twice a year to suppress the overall population by 80 to 90 percent. The second step is to use the faster-acting mound treatments described previously to eliminate any nuisance mounds that survive the bait or appear between broadcast applications.
An alternative to baits is a broadcast application of a granular contact insecticide over the entire lawn surface for seasonal control. These treatments can provide a barrier that eliminates foraging ants for months, but they are generally more expensive and may not eliminate colonies nesting deep in the soil. Finally, habitat modification can make the area less inviting to new colonies by removing debris, such as logs or stones, that ants use for nesting sites. If an infestation is widespread, involves inaccessible areas, or proves resistant to treatment, consulting a licensed pest control professional is the best course of action.