The fire ant (red imported fire ant, Solenopsis invicta Buren), is an invasive insect whose sting can cause serious problems. Where imported fire ants are common, most homeowners recognize them by the mounds they build or the stings they inflict. However, there are also other characteristics to look for. Their aggressive nature compared to other ant species is one such trait. If a mound is disturbed, usually hundreds of fire ant workers will swarm out and run up vertical surfaces to sting. These ants are social insects and unlike many insect pests, they are very organized. Fire ants are aggressive and will defensively attack anything that disturbs them. Fire ants can sting repeatedly. Symptoms of a fire ant sting include burning, itching and a white, fluid-filled pustule that forms a day or two afterward.
Colonies consist of the brood and several types (castes) of adults. The whitish objects often found at the top of the mounds are actually the ant’s developmental stages or brood— the eggs, larvae and pupae.
Imported fire ants interfere with outdoor activities and harm wildlife throughout the southern United States and elsewhere. Fire ants from colonies close to homes and other buildings sometimes forage indoors for food and moisture, particularly during the hot, dry, summer months. Entire colonies occasionally nest in wall voids or rafters, or behind large appliances, sometimes moving into buildings during floods or drought. They are a nuisance and can threaten sleeping or invalid people and pets. Fire ants frequently infest electrical equipment. They chew on insulation, can cause short circuits, and can interfere with switching mechanisms. Air conditioners, traffic signal boxes, and other devices all can be damaged. Fire ants also nest in the metal housings that surround electrical and utility equipment. They frequently move soil into these units, which can cause corrosion, electrical short circuits, and other mechanical problems. Ants occasionally feed on vegetable plants in home gardens. They tunnel into potatoes underground and feed on okra buds and developing pods. The worst damage usually occurs during hot, dry weather. Ants may be a nuisance to gardeners during weeding and harvesting.
Although fire ants do prey on flea larvae, chinch bugs, cockroach eggs, ticks and other pests, the problems they cause usually outweigh any benefits in urban areas.
Properly identifying an ant species is the first step in determining whether the ants should be managed and how to do so. While it may not be possible to eradicate fire ants, controlling them is highly desirable. The best control programs use a combination of non-chemical and chemical methods that are effective, economical, and least toxic. Most management options require repeated treatments to maintain control. If you treat and your neighbor does not, you will find your yard is quickly re-infested. If you educate your neighbors, you can coordinate your battle against the imported fire ant more effectively and efficiently.
Many home remedies have been tried and while these methods sometimes appear to work, they rarely eliminate colonies. Disturbing (or knocking down) mounds frequently will cause colonies to move. Some people believe shoveling one mound on top of another will force ants to kill each other, but this is not true. Sprinkling grits or other solid food substances onto fire ant mounds is ineffective. It has been suggested that when the ants eat the grits their stomachs will swell and rupture. In fact, only the last larval stage of the developing fire ant is known to digest solid food. All other life stages feed only on liquids or greasy materials. Gasoline and other petroleum products do kill some fire ant colonies. However, petroleum products are dangerously flammable or explosive, kill grass and plants around the treated mounds, and can seriously pollute the soil and ground water. Using petroleum products, solvents, battery acids, bleaches or ammonia products can be dangerous and is strongly discouraged. Pouring very hot or boiling water on a mound is a fairly effective treatment, particularly when ants are close to the mound surface such as on a cool, sunny morning or after heavy rainfall. Approximately 3 gallons of very hot (almost boiling) water poured on each mound will eliminate about 60 percent of the mounds treated. Be careful handling large volumes of hot water to prevent serious burns, and keep hot water off of desired plants and grass. Individual mounds can be carefully shoveled into a bucket dusted on the inside with baby (talcum) powder and the ants drowned with soapy water, but this rarely eliminates all ant colonies in the area.
Taken from Managing Imported Fire Ants in Urban Areas, Texas AgriLife Extension