In general, ants do not often directly injure turfgrass, but the presence of colonies that form areas cleared of turfgrass or mounds of dirt can appear unsightly and become troublesome by interfering with golfing or field operations such as mowing. Galleries constructed by colonies can disrupt turfgrass roots and change the moisture-holding capacity of soils. In some habitats, ants move as much or more soil as earthworms, thereby helping to reduce soil compaction (Holldobler & Wilson 1990). Some ant species, such as the red imported fire ant, can sting repeatedly and are medically important.
Hypersensitive individuals can experience severe reactions to stings, although more commonly victims may develop secondary infections when stings become infected. Serious incidents occasionally result in liability lawsuits involving managers or owners of public access areas. Harvester ants also inflict a painful sting. Ants nesting in turfgrass areas can also cause problems when foraging ants or migrating colonies enter sites where their presence is unwanted. Red imported fire ants nesting in turfgrass can invade homes and buildings, electrical equipment and utility housings, home gardens, compost piles, mulched and flower beds (Drees et al.1996).
Ants can be found in almost any type of turfgrass, and colonies can occur in lawns, parks, playgrounds, golf courses as well as agricultural land and wilderness areas. Ants feed on a wide variety of materials, although certain species show certain preferences. Harvester ants feed primarily of parts of seeds (nutritious caps or sheaths of seeds), while fire ants primarily consume other arthropods, including some turfgrass pests such as chinch bugs (Crocker et al. 1995, Drees et al. 1996). The Texas leafcutter ant clips parts of leaves from trees and shrubs, which they carry back into their colonies and use to culture a fungus which they eat. Some ant species feed on the honey secretions of aphids and other Homoptera, protect these insects from natural enemies and promoting infestations. In the southern states, the pyramid ant feeds primarily of dead ants, such as dead harvester ants, discarded by other colonies (Holdobler & Wilson 1990).
Colonies of ants often form characteristic soil disturbances and mound shapes are often characteristic to species. Several harvester ant species, such as the red harvester ant, produce nests in open, sunny areas that are flattened 1 meter diameter circular areas cleared of vegetation, covered with course gravel and with a one or a few central nest openings. The Texas leafcutting ant builds “towns” characterized by a high concentration of terrace-topped mounds made of course soil aggregates and having central openings. Both types of ants often produce long (i.e., 7 meters) foraging trails cleared of vegetation. The Allegheny mound ant (not found in Texas) can construct mounds that are up to 0.9 meters high and more than two meters across (Borror et al.). Pyramid ants are smaller (1/8 inch long) black ants that build small mounds of fine soil and terraces around central openings.
In Texas and other parts of the southeastern states, red imported fire ant mounds can become very numerous, particularly in areas infested with the multiple queen (polygyne) form (Greenberg et al. 1985, Porter et al. 1991). Mounds are common in open sunny areas. Drees and Vinson (1990) reported mound densities averaging 1,635 per ha. + 573.5 SD in a pasture invested with the multiple queen (polygyne) form in Brazos County, Texas, whereas a single queen (monogyne) infested pasture in Montgomery County averaged 72 per ha. + 19.0 SD. Mound diameters averaged 46.4 cm + 10.1 SD and 50.1 + 13.1 SD for the two areas, respectively. In most regularly mowed turfgrass areas, mound height is less important than numerous mound sites where grass becomes covered with soil during periods of the year when ants actively excavate dirt to build mounds. Regular disturbance of colonies by activities such as frequent mowing often cause colonies to migrate to neighboring, undisturbed areas. Left undisturbed, mounds can become very large and tall (i.e., 35 cm tall and 25 cm in diameter) (Note: Lofgren et al., Annual Review of Entomology 20:1-30, reported mounds up to 1 meter tall and 1 meter wide). Below ground, nest galleries can penetrate in a V-shaped pattern below the nest, penetrating as much as 1.2 meter deep in the soil (Sparks 1995). Soil type, availability of soil moisture and other factors affect the height, diameter and structure of mounds.
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.
Drees, B. M. And S. B. Vinson. 1990. Comparison of the control of monogynous and polygynous forms of the red imported fire ant (Hymenoptera: Formicidae) with a chlorpyrifos mound drench. J. Entomol. Sci. 25(2): 317-324.
Drees, B. M., C. L. Barr, S. B. Vinson, R. E. Gold, M. E. Merchant and D. Kostraun. 1996. Managing red imported fire ants in urban areas. B-6043. Texas Agric. Ext. Serv., The Texas A&M Univ. System, College Station, Texas. 18 pp.
Greenberg, L. D., J. C. Fletcher and S. B. Vinson. 1985. Differences in worker size and mound distribution in monogynous and polygynous colonies of the fire ant Solenopsis invicta Buren. J. Kans. Entomol. Soc. 58(1): 9-18.
Holldobler, B. & E.O. Wilson. 1990. The Ants. The Belknap Press of Harvard University Press, Cambridge, Massachusetts. 732 pp.
Porter, S. D., A. Bhatkar, R. Mulder, S. B. Vinson and D. J. Clair. 1991. Distribution and density of polygyne fire ants (Hymenoptera: Formicidae) in Texas. J. Econ. Entomol. 84(3): 866-874.
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.
MEDICAL & VETERINARY PROBLEMS FROM IMPORTED FIRE ANT STINGS
(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.)
Also see Medical Problems Associated with the Red Imported Fire Ant and Texas Pest Ant Identification: an Illustrated “Key” (010), Diagnosing and treating animals for red imported fire ant injury, 4 pp.).
Fire ants are aggressive when disturbed and will defensively attack anything that disturbs their mounds or food sources. Because of this, people are often forced to alter outdoor activities when fire ants are present. Fire ants can sting repeatedly. Multiple stinging incidents have been reported on impounded animals, infants, and bed-ridden adults. Symptoms of a fire ant sting include burning and itching. The ant injects a venom containing an oily alkaloid called Solenopsin A that is toxic to cells. It causes a white pustule to form in a day or two. Although the stings are not usually life threatening, they are easily infected and may leave permanent scars. Some people become sensitive to fire ant stings and should seek the advice of an allergist. If a sting leads to chest pains, nausea, severe sweating, loss of breath, serious swelling, or slurred speech, the person should be immediately taken to an emergency medical facility. Some people may lapse into a coma from even one sting. Relatively few deaths from fire ant stings have been documented, compared to deaths from bee and wasp stings.
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See Factsheets and Publications
Borror, D. J., C. A. Triplehorn, and N. F. Johnson. 1989. An Introduction to the Study of Insects. Sixth Ed., Saunders College Publishing, New York. 875 pp.
Brook, T. S., C. C. Carter, P. P. Cobb, C. S. Goruch, K. R. Horn, L. T. Lucas, K. Pinkston, D. K. Polet, R. Price, R. L. Robertson, R. A. Scheibner, H. E. Williams. 1982. Insect and other pests associated with turfgrass (J. R. Baker, ed.). AG-268. North Carolina Agric. Ext. Serv., North Carolina State University, Raleigh, North Carolina. 108 pp.
Drees, B. M. and J. A. Jackman. 1998. A Field Guide to Common Texas Insects. Gulf Publishers, Houston, Texas. 359 pp.
Greenberg, L. D., J. C. Fletcher and S. B. Vinson. 1985. Differences in worker size and mound distribution in monogynous and polygynous colonies of the fire ant Solenopsis invicta Buren. J. Kans. Entomol. Soc. 58(1): 9-18.
