The black imported fire ant, accidentally imported from South America into Mobile, Alabama, was first reported in 1918. Its distribution is still restricted to parts of Mississippi and Alabama. The red imported fire ant was imported around the 1930’s and has spread to infest more than 260 million acres of land in nine southeastern states, including all or portions of Florida, Georgia, South Carolina, Tennessee, Alabama, Mississippi, Arkansas, Texas and Oklahoma (Lofgren 1986, Sparks 1995). This species has become very abundant, displacing many native ant species when abundant. It has the potential of spreading west and surviving in southern Arizona and along the Pacific coast north to Washington (Vinson & Sorenson 1986).

Ants occur throughout the world. Harvester ants occur west of the Mississippi river and in the south, with common species including the western harvester ant, Polygomyrmex occidentalis (Cresson), the red harvester ant, P. barbatus (F. Smith), the California harvester ant, P. californicus (Buckley) and the Florida harvester ant, P. badius (Latreille)(Crocker et al. 1995). The Texas leafcutting ant occurs in the eastern half of Texas and west-central Louisiana (Stewart 1982). In the northeastern states, the cornfield ant, thepavement ant, the red ant and the Allegheny mound ant are the common species of colonizing turfgrass areas. Many species of ants that occur in turfgrass are native to the United States.

Crocker, R. L., R. M. Marengo-Lozada, J. A. Reinert & W. H. Whitcomb. 1995. Harvester ants. pp. 64-66. In Handbook of Turfgrass Insect Pests (R. L. Brandenburg and M. G. Villani, eds.). The Entomol. Soc. Amer. Landham, Maryland. 140 pp.

Lofgren, C. S. 1985. The economic importance and control of imported fire ants in the United States. Pp. 227-256. In Economic Impact and Control of Social Insects (S. B. Vinson, ed.) Praeger Publishers, New York.

Stewart, J. W. 1982. Texas Leaf Cutting Ant. L-1222. Texas Agricultural Extension Service, Texas A&M University System, College Station, Texas.

Sparks, B. 1995. Red imported fire ant. pp. 84-85. In Handbook of Turfgrass Insect Pests(R. L. Brandenburg and M. G. Villani, eds.). The Entomol. Soc. Amer. Landham, Maryland. 140 pp.

Vinson, S. B. & A. A. Sorenson. 1988. Imported Fire Ants: Life History and Impact. Texas Department of Agriculture, Austin, Texas. 28 pp.

Additional reading:

Lofgren, C. S., W. A. banks and B. M. Glancey. 1975. Biology and Control of Imported Fire Ants. Annual Review of Entomology 20:1-30.

Vinson, S. B. (ed.). 1986. Economic Impact and Control of Social Insects. Praeger Scientific, New York.

Vinson, S. B. 1997. Invasion of the red imported fire ant. American Entomologist 43(1):23-39.

HISTORY AND CONTROL EFFORTS

(from: Drees, B. M., C. L. Barr, S. B. Vinson, R. E. Gold, M. E. Merchant and D. Kostroun. 1996.

Managing red imported fire ants in urban areas. B-6043.

Texas A&M University, College Station, Texas. 18 pp.)

Since its accidental introduction from South America to Mobile, Alabama over 60 years ago, the red imported fire ant has spread to infest over 260 million acres comprising most of nine southeastern states and Puerto Rico. Reaching Texas during the 1950’s, the fire ant spread steadily across the state, dispersing naturally through mating flights, mass movement of colonies, and floating to new locations in flood water. Fire ants can travel long distances when newly-mated queens land on cars, trucks or trains. Shipments of nursery stock or soil from an infested area may relocate entire colonies or nests. The fire ant presently infests the eastern two-thirds of Texas and continues to spread westward.

Early efforts of county-wide fire ant eradication during the late 1960’s through the early 1970’s used insecticides such as heptachlor and mirex, but fire ants persisted and returned to areas previously treated. The last large-scale aerial treatments were applied to Madison, Kerr and Kendall counties in 1981 and 1983 using Amdro® (hydramethylnon) and Pro-Drone.

WHY DID EARLIER ERADICATION PROGRAMS FAIL?

Attempts to eradicate the imported fire ant in the 1960s and 70’s, using a very effective pesticide bait and involving large-scale programs, failed. The reasons for the failure are debatable. At present, any serious consideration of eradication as a goal is hindered by some facts of the ant’s biology and by problems with treatment methods.

Biological reasons prohibiting chemical fire ant eradication. The ants infest such an extensive area that a single treatment would take years and massive resources. Fire ants have a high reproductive rate and effective dispersal mechanisms. Thousands of reproductive females are produced per colony. Each year after warm rains, these females fly and mate with flying males. The mated females then begin a colony wherever they land. The ants eliminate competing insects and then rapidly overwhelm an area. Whole colonies can move, and in the multiple queen form, the colonies can split into many new colonies. The queen is protected from many toxicants, since she is only fed food eaten first by workers. If a poison works too rapidly, the worker is killed before the poison is passed to the queen. Finally, worker ants from well-fed colonies may not forage on a bait product, or a bait may not be as attractive as some particular abundant food source. Consequently, the ants may not get the poison.

Pesticidal reasons prohibiting chemical fire ant eradication. All pesticidal approaches may be expensive in time, equipment, or product cost. Although there are many products for red imported fire ant management, there are only three basic approaches. The first is thesurface treatment using a residual contact poison. This approach is the least environmentally sound because long residual poisons must be used and the surface remains toxic for long periods. The ants may survive by foraging underground. The second isindividual mound treatmentwhich involves the application of a large volume of pesticide to reach the queen. However, it is hard to manipulate large volumes of liquid, and treatment is more expensive and time-consuming. Colonies not eliminated may move or split into several colonies. The third method is bait treatments which use some sort of attractive substance the ants like to eat. Unfortunately, baits are not always consumed, and the baits attractiveness is short lived. Although baits can be applied as a mound treatment, their advantage is that they can be applied quickly over a large area. However, area-wide application can result in missed colonies. The pesticide must be slow-acting and effective over a range of doses, since the dose the ants get cannot be controlled (particularly important for baits). Further, the available treatments can reduce competitors, if present, which help control the fire ant.

Economic, regulatory and environmental obstacles for chemical fire ant eradication. The best way to treat large areas (hundreds of acres) is aerial application. However, not all areas where fire ants reside can be treated because of label restrictions and application limitations. Untreated areas serve as sources for reinfestation. Even with a bait product, it is not feasible to treat the entire infested area or even part of a single state. Yet, the larger the treatment area, the slower reinfestation occurs. If periodic treatments are discontinued, fire ants reinvade previously treated “open” areas. The result is many small infested locations that expand over a year or two and result in a resurgence of the problem.