The red imported fire ant (RIFA) probably entered the United States (U.S.) in the 1930s in materials shipped from Brazil, Paraguay, and Argentina. By 1985, RIFA had spread from their point of entry in Mobile, Alabama, to much of the southern U.S. In November of 1998, California’s first colony of RIFA was discovered in Orange County. As of January 2007, colonies of RIFA have been found in areas of Orange, Riverside, Los Angeles and San Bernardino Counties. Isolated RIFA colonies associated with agricultural production are currently under treatment in Fresno, Madera, Merced, and Stanislaus Counties.

RIFA generally live in soil and their mounds or colonies can reach 50 centimeters (18 inches) in height. RIFA need water to survive, so colonies are often found near water.

Colony sites include rotting logs, at the base of stumps and trees, under sidewalks and pavement, and in and around buildings. RIFA also will infest electrical equipment and utility housings. Colonies frequently migrate from one site to another. Colonies typically have 100,000 to 500,000 workers and several hundred winged reproducers. The sterile worker lives about five weeks, whereas a queen ant may live several years. A single colony may harbor several queens. A queen needs only six workers to start a new colony.

Known for their aggressive behavior, RIFA can interfere with outdoor activities and can be harmful to domestic livestock and native wildlife. RIFA will readily sting in defense of the colony. If a mound is disturbed, thousands of workers will swarm out in defense. Tens and possibly hundreds of stings can result. Sting symptoms include burning and itching, which subside in about 60 minutes. A small blister forms in about four hours and a white pustule forms in a day or two. A systemic allergic reaction to the sting can occur if a person is hypersensitive to the stings. Hypersensitivity may be characterized by a number of symptoms, including flushing of the skin, general hives, swelling of the face, eyes, or throat, chest pains, nausea, severe sweating, and difficulty breathing or speaking. Persons experiencing these symptoms must immediately seek emergency medical assistance.

The native southwestern fire ant is not as serious a pest as the RIFA. The southwestern fire ant is not as aggressive and its sting is not as severe. The RIFA will out-compete and displace the native southwestern fire ant when the two ants come into contact with each other.

RIFA stings should be washed vigorously with soap and water to prevent secondary infection. Application of cold compresses may help to reduce swelling and pain.

Over-the-counter topical steroid ointments and oral antihistamines may relieve itching. Sting victims who experience more severe, systemic symptoms should consult with their physician.

RIFA are attracted to, consume, and contaminate sweets, grains, meat, butter, cheese, nuts, grease, and jellies or jams. They will ring the bark of fruit and nut trees and gnaw roots, stems, and leaves of agricultural crops. They will attack and kill young livestock (e.g., cattle, pigs, rabbits, chickens, ducks, and quail). The presence of RIFA can hamper workers harvesting crops. The mounds can cause damage to agricultural equipment and pose a risk of injury to animals and humans.

Children should be taught about fire ants and their hazard. Persons allergic to fire ant stings should wear closed shoes, socks, a long-sleeved shirt, long pants, and gloves in areas where there may be a chance of being stung. Pets should not be tied or caged near RIFA colonies.

Fire ant colonies near the home should be located and treated with an over-the-counter ant bait insecticide. If the infestation is large, ask for professional advice from the local agricultural commissioner’s office or a pest control company. Contact local county pest control agencies by calling the statewide RIFA hotline phone number established by the California Department of Food and Agriculture at 1-888-434-7326.  ​​​