Imported fire ants (Solenopsis invicta and Solenopsis richteri) are invasive species that cause $6 billion in annual losses in the United States ( See Area Wide Fire Ant Suppression). Imported fire ants inflict painful stings and can kill human beings. There are large social and medical costs associated with this pest. The large mounds they build dot the landscape (average of 60 mounds per acre from Louisiana eastward, and 300 mounds per acre in Texas). The mounds are unsightly and can damage mowers and combines. Fire ants invade electrical equipment, causing short circuits and equipment failures. They cause ongoing expense to turfgrass managers. Currently, a USDA APHIS quarantine covers 320,000,000 acres in 14 U.S. states or territories. -- Alabama Extension Service
Fire ants are found in at least 14 of the lower 48 states, California and Puerto Rico. I hope you have none.
Many aspects of imported fire ants can be beneficial, but they can cause many problems. In urban areas, imported fire ants cause problems because of their unsightly nests or mounds often found in open, sunny areas. The ants have an affinity for electrical equipment and can cause failures when they interfere with switching mechanisms, chew on insulation, and fill utility boxes with soil for nesting. --Alabama Extension Service
My friend Burt had to have her heat pump replaced when fire ants nested in the condenser.
In agriculture, their tall, hardened mounds can interfere with field working machinery. Although fire ants eat certain insects, they protect and encourage population growth among sucking insects such as aphids, scales, mealybugs, and others that produce the sugary liquid called honeydew. The ants feed on the honeydew rather than eat the insects that produce it. Thus, they can increase the need for insecticide use for these pests in certain crops such as cotton and ornamental crop nurseries. -- Alabama Extension Service
Fire ants love my garden and 'farm' aphids and other insects for their purposes, ruining ornamentals like gardenias. These gardenias are from my garden, 2009. I look forward to more blossoms in June.
There is extensive information on controlling fire ants on the Alabama Extension site. Some other states have similar information. The most important thing that I took from this site was that the best way to insure that one is using approved baits is to buy from reputable dealers who will not be selling chemicals not licensed in the state.
Alabama Extension Service Fire Ant Control Web Site
Effective organic controls for imported fire ants that work and are available are few. Folk tales abound, as do fire ants. I've doused them with boiling water. I've taken shovelfuls of soil from one mound and transferred to another to let 'em duke it out. I've sprinkled the mounds with grits in hopes swollen corn bits would do whatever it was supposed to do. I've let the armadillo population increase in hopes they would destroy entire mounds instead of just stirring in them and eating a few. I've poured various botanicals over the mounds. Mostly the ants just pack up and move a few feet away.
Spinosad is considered organic because it is produced from a bacterial fermentation process that produces a toxin, which extracted and put into a bait. Spinosad baits work well in small areas or as mound treatments, achieving control in 2 to 4 weeks. Spinosad costs about $8 to $10 per pound.
Releases of Thelohania solenopsae, a disease-causing protozoan that attacks the imported fire ant and came along with the ant when it came into the US, were made in 10 southern states. Currently there are no commercial products containing Thelohania available. There are questions concerning Thelohania getting into coastal waters and affecting crayfish.
Fire ant bait is one of the few exceptions I make to having a pesticide-free garden.