Fire Ants in the Yard: Identification, Quarantine, Control

Imported fire ants build soil mounds with no opening in the center, and they swarm out to sting when a mound is disturbed; within about a day, a sting often turns into a white pustule. The ants are covered by a federal quarantine that, as of August 2025, includes all or parts of 13 states and Puerto Rico. For yards with many mounds, Texas A&M AgriLife Extension recommends a two-step approach: broadcast bait over the whole area, then treat problem mounds directly.

How to recognize imported fire ants

NC State Extension describes red imported fire ants as reddish to dark brown, with workers in the same colony ranging from about 1/8 inch to about 1/4 inch long. Texas A&M AgriLife Extension calls that variation in size a distinguishing characteristic of imported fire ants.

The mounds are the other field mark. Unlike most ant mounds, Texas A&M notes, they have no opening in the center; the ants come and go through underground tunnels. In clay soils they are usually symmetrical domes and in sandy soils often irregular, according to NC State. Fresh mounds of fluffy, worked soil are easiest to spot a few days after a heavy rain.

Two species arrived from South America, the red imported fire ant and the black imported fire ant, according to a University of Arkansas Cooperative Extension fact sheet. The red species is the more widespread.

Stings and health

Fire ants sting repeatedly, and the venom burns. CDC’s National Institute for Occupational Safety and Health (NIOSH) says red bumps form at the sting site and develop into white, fluid-filled pustules within a day or two. NC State Extension notes that a small number of people are highly allergic to the stings and need urgent medical attention.

NIOSH lists signs of a severe reaction that need emergency care at once: severe chest pain, nausea, severe sweating, loss of breath, serious swelling or slurred speech. Call 911 or get to an emergency medical facility immediately. Anyone who has reacted badly to stings before can ask a physician how to prepare.

What the federal quarantine covers

The quarantine restricts moving soil, plants, sod, hay and earth-moving equipment out of quarantined areas; it does not regulate how a homeowner treats a yard. The U.S. Department of Agriculture runs it to slow the spread of imported fire ants by people.

In a Federal Order dated August 19, 2025, its Animal and Plant Health Inspection Service (APHIS) removed Doña Ana County, New Mexico, from the quarantine after three consecutive years of negative surveys. With that change, the states still federally regulated are Alabama, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas and Virginia, plus Puerto Rico. The quarantine takes in all of some of these states and only listed counties of others, and APHIS publishes the full list of quarantined areas on its imported fire ant web page.

The Arkansas extension fact sheet on the quarantine lists the regulated articles as soil, potted or balled plants other than house plants, nursery stock, grass sod, baled hay and straw, and earth-moving equipment. Moving them from a quarantined area to an unquarantined one requires a certificate. The same fact sheet notes that, realistically, the rule does not apply to a homeowner buying a plant at a local store. Anyone planning to move sod, soil or nursery plants out of a quarantined county can check the requirements with the state plant protection agency or a county extension office.

Fire ants can also damage equipment. The Arkansas fact sheet notes that they sometimes short-circuit electrical equipment such as air conditioners.

The two-step method

The two-step method pairs a yard-wide bait broadcast with direct treatment of problem mounds. Texas A&M AgriLife Extension recommends it for yards and neighborhoods, and its fact sheet states that, applied properly, the method poses little risk to people or pets.

Step 1: broadcast bait over the whole yard. A fire ant bait is food combined with a slow-acting insecticide. Foraging ants carry the particles into every colony, including mounds that are not visible, and share them with the queens. Baits work only while ants are foraging, which Texas A&M says happens when the soil surface is between 70 and 90°F. Its fire ant project’s web page suggests broadcasting sometime between late August and mid-October, when the ground and grass are dry and no rain is expected for 24 to 48 hours, usually in the late afternoon or evening.

Bait has to be fresh. The fact sheet gives unopened containers a shelf life of about 2 years and says an opened container should be used within a month or two. It suggests a test: sprinkle a little next to an active mound, and if ants start carrying it off within 30 minutes, it is fresh enough to use. In summer, fire ants forage mostly at night, so the fact sheet advises applying bait in the evening during hot weather; bait put out when daytime soil temperatures exceed 90°F loses its effectiveness.

Step 2: treat problem mounds. Mounds next to the foundation, in high-traffic areas or in other sensitive spots can be treated directly with a drench, granules, dust or bait, following the label. For granules and liquid drenches, the fact sheet calls for 1 to 2 gallons of water per mound, so the insecticide reaches deep into the nest where the queen lives. Texas A&M advises against disturbing a mound during treatment and warns never to use gasoline or other petroleum products on fire ants.

How long control takes

Fire ant baits are slow by design. Texas A&M’s fact sheet says baits containing indoxacarb, hydramethylnon or spinosad control fire ants within 2 to 4 weeks, while baits built on insect growth regulators usually need 2 to 6 months. Its web guidance says baits take weeks to months to reach 80% to 90% control, and should be reapplied once or twice a year.

A treated yard can be reinfested from the land around it. Texas A&M notes that reinfestation takes longer when larger areas, and several neighboring yards, are treated together.

When to call a professional, and what to ask

Texas A&M’s fact sheet says the two-step approach may not suit a small yard with few mounds, or a household that needs a higher level of control, such as one with a person highly allergic to stings. It adds that hiring a pest control company to treat a neighborhood can make sure treatments are applied properly and on time. Questions worth asking:

• Which bait active ingredient will you use, and how long before the mounds should decline?
• Will you broadcast bait across the yard, treat individual mounds, or both?
• How will you handle mounds against the foundation or near air-conditioning equipment?
• How many applications a year does the plan include, and in which months?
• Which license category covers lawn and yard applications in this state, and does your applicator hold it?