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This is the first of two articles about red imported fire ants (RIFA). Part Two will be published October 2018.

Red imported fire ant on pencil. Photo by Jack Kelly Clark, courtesy University of California Statewide IPM Program.

By Vincent Lazaneo.

Stroll, play, or picnic on a lawn at a local park or school and you could have a very painful and possibly life-threatening encounter with red imported fire ants (RIFA), a dangerous and destructive new pest in the county. The invasive ant usually lives outdoors in irrigated areas and near natural sources of water, but will occasionally nest in the walls of homes. RIFA damages plants and can eat a wide array of plant and animal material. Disturb a colony’s nest or its food source and fire ants will quickly live up to their name.

When a person or animal accidentally steps on a nest, dozens of ants swarm onto the victim. Each ant bites the skin with its sharp mandibles to anchor itself, then delivers multiple stings as it pivots. The venom produces intense pain, like being poked with a hot needle, and an itching sensation. Small blister-like sores appear in a few hours and become white, fluid-filled pustules that take weeks to disappear. Scratching the pustules or not keeping them clean can cause infection and may leave permanent scarring.

For people who are hypersensitive to RIFA venom, the stings can be life-threatening. As many as two people in one hundred have a systemic allergic reaction after a stinging incident. Immediate medical attention should be obtained if a victim experiences: flushing of the skin; general hives; swelling of the face, eyes or throat; chest pain; nausea; severe sweating; and difficulty breathing or speaking.

Red imported fire ant workers tending a dark-winged reproductive female. Photo by Jack Kelly Clark, courtesy University of California Statewide IPM Program.

People who are not familiar with RIFA may mistake them for other ants found in our area. RIFA are a dark, reddish-brown color and vary in size from 1/16 to 1/5 inch long. They usually nest where the ground is moist and create low mounds of fine soil, spanning two to eighteen inches across, that resemble gopher mounds. Native southern fire ants, on the other hand, are about the same size and color as RIFA, but their nests are usually irregular in shape with scattered soil and multiple obscure entrances. The California harvester ant is also red, but the workers are all the same size—about 1/5 inch long. See the UC Pest Note, Red Imported Fire Ant, for more information on how to identify RIFA.

Isolated RIFA colonies have been eradicated in some parts of San Diego County, but more widespread infestations have persisted. RIFA colonies have been found on the Miramar Air Base; at Mira Mesa Senior High School; and along the Black Mountain Road corridor at sites including Miramar College, Wangenheim Middle School, Westview Park, and Breen Park. The ant has also been found at the Bernardo Heights Middle School, in the Point Loma/Rosecrans area, and in Poway.

Agricultural officials believe RIFA colonies are probably on private properties, but no reports from homeowners have been received by the County's Department of Agriculture, Weights and Measures (AWM). If you find RIFA, it’s best not to treat them yourself. County personnel will assist in identifying RIFA and will treat colonies at no cost to you.

Call 1-800-200-2337 to obtain information and leave a message. At least ten ants in a sealed jar with or without alcohol can be submitted for identification on weekdays at AWM's San Diego office, or at the North County office.

Vincent Lazaneo is UC Urban Horticulture Advisor Emeritus. He has a master’s degree in horticulture and a teaching credential in vocational agriculture from UC Davis. In 1983, Vince began the Master Gardener program in San Diego. Vince frequently contributes, or has contributed to, the San Diego Union-Tribune, Mira Mesa Living, and other publications. He enjoys growing specialty plants in his home garden, reading, hiking, and fishing.

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