Control methods to fight fire ants

Spot the mound Fire ant mounds can be as large as 3 feet in diameter. (Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org)

Want to know the best way to identify a fire ant infestation? Look for the shape of the mounds, experts say. LM talked to Brian Mount, technical service manager for FMC Corp., and Laurence Mudge, Green Solutions Team manager for Bayer, about this common pest in the South and Southeast.

“Fire ant mounds can be rather flat in sandy soils and many inches high in heavier soils,” Mudge says. Mounds can range from a few inches high to more than a foot and have a diameter of a few inches up to 3 feet or more, Mount says.

Identified by their reddish-brown color and two nodes between the thorax and abdomen, fire ants also have a fiery response when provoked, unlike other ant species.

“Fire ants are extremely aggressive and will swarm out of the mound when disturbed,” Mudge says.

Fire ants get their name from the propensity to bite, which makes them more than a nuisance in the open grassy areas they like to colonize. “Fire ant ID is important as there are many other ant species that invade turf that do not cause a problem,” Mudge says. “In fact, these native ants are competitive with fire ants and can help keep fire ants at bay.”

Control methods

Spring is the best time to control fire ants using a two-part program of mound treatments and blanket insecticide treatments.

Baits work from one to eight weeks and are designed to be slow-acting as the adult ants carry the bait back to the mound. There, they feed it to the larvae, which converts it to food for the adult ants, according to information from the Mississippi State Extension program. Indoxacarb and hydramethylnon are faster-acting granular baits. Treatments to mounds can be a dry or liquid drench applied directly to the mound. Broadcast treatments should be applied with a spreader and can be either bait or nonbait products.

A nonbait granular insecticide with the active ingredient fipronil can provide up to 12 months control, Mudge says. Granular products containing bifenthrin, gamma-cyhalothrin, cyfluthrin or permethrin can provide four to six months control according to Mississippi State, and liquid products also contain active ingredients bifenthrin, cyfluthrin, gamma-cyhalothrin or permethrin.

“First, treat a 2-to-3-foot band around any mounds to prevent ants escaping the mound as it is treated,” Mount says. “Second, treat the mound with enough force to break the apex and penetrate deep into the mound. Mounds of 12 inches in diameter or less may require up to 1 gallon of treatment, while larger mounds may require up to 2 gallons of treatment. Last, broadcast treat the property with a residual insecticide to prevent future infestations.”

As you’re treating for fire ants, scout the property for mounds under shrubs and along building foundations. Mississippi State Extension suggests not disturbing the mound prior to treatment as worker ants may move the queen to safety.

“A fire ant program may require three to five treatments throughout the year to prevent reinfestation,” Mount says.