Species & Identification

Several native fire ant species, black imported fire ant, red imported fire ant and their hybrid can be found in the United States. The fire ant species of concern in South Carolina is the red imported fire ant (RIFA). Therefore, this factsheet will focus on RIFA.

A worker ant is about 1/8 to ¼ inch (2.5 to 6 mm) long and red to blackish red. RIFA can be distinguished from other native fire ant species by the two‑segmented pedicel or “waist” between the thorax and abdomen. RIFA mounds are easily recognizable due to their characteristic dome shape and apparent lack of an entrance hole. The mounds of native ant species are lower and have an apparent hole for entry and exit.

RIFA is distributed from southeastern Virginia through Tennessee, southern Missouri and Oklahoma to Texas. Isolated populations are also found in southern New Mexico and California.

Damage & Symptoms

RIFA do not feed on turfgrass. However, their mounds can cover and smother turf, disrupt the playing surface, and damage or clog mowers. Their painful sting is highly hazardous and a serious medical problem to people and pets. Some people can have severe allergic reactions to the sting. When a mound is damaged, fire ants will pour out of the mound in a defensive action. In addition to open fields, mounds may be located near rocks, pavement, stumps and rotten logs as these structures can help protect the mounds.

Life Cycle

A colony is established by a single mated female or queen. Reproductive winged males and females, called alates, disperse from the parental colony and perform mating flights when air temperature is consistently between 70 and 95°F and after rain or when rain is expected. Males die following mating and females will land approximately 1 to 2 miles from their parental colony. Once landed, the newly mated queen will shed her wings and search for a suitable place to form a nest. A new queen will first form a waterproof chamber where she will lay the first batch of eggs (between 45 and 150 eggs) of her new colony. The new queen nurses the first batch of eggs to adulthood. Once new workers reach adulthood, they become builders, caretakers, foragers and defenders of the colony. The queen now transitions to focus solely on laying eggs, which can be as many as 1,500 eggs per day. A queen can live for 2 to 6 years and workers live for 30 to 180 days.

Scouting

RIFA is easily scouted for by looking for their characteristic dome‑shaped mound. These mounds can be lower and not dome‑shaped if the mounds are frequently disturbed or flattened. Disturbing a mound will result in a flood of workers rushing to the surface to defend their nest. Developing colonies without visible mounds are impossible to detect. Foraging activity of the RIFA can be scouted for (to time bait application) by placing a small piece of hotdog, potato chip, cookie or any oily food on a piece of paper or a dish, leaving it on the ground, and returning in 20 to 30 minutes to observe for ants on the food item.

Cultural Control

Severe mechanical disruption of a mound can temporarily reduce activity. However, the colony will rebuild mounds near the original mound in a short period of time. While pouring hot water directly onto the mound can also kill ants, the logistics of transporting hot water across a lawn may be difficult, not to mention dangerous. Do not pour chlorine, ammonia or fuel onto the mounds as these practices are dangerous and can contaminate groundwater.

Biological Control

Several biological control options are being tested, including parasitic phorid flies and disease‑causing microsporidia. Phorid flies lay an egg behind an ant’s head. The larva kills the ant several weeks later, cuts off the head, and pupates inside the severed head. Workers are less likely to forage and build new mounds in the presence of phorid flies. These biological control agents are not currently available to the general public. Several biopesticides containing the fungus Beauveria bassiana are available for use in lawns and other turfgrass sites. Fungal spores attach to the ant’s exoskeleton, and upon germination, colonize the ant and eventually kill it. This method works best when applied directly to individual ants rather than being broadcast on the soil surface.