Red imported fire ants were accidentally brought to the United States. Scientists think the ants arrived near Mobile, Alabama in the 1930's or 1940's. Since the ants were originally from South America, there were no natural predators in the United States.
With no predators to slow them down, the fire ants spread across the southern states. Now they are established from the Carolinas to California. There is some disagreement over the northern limit of their movement. They have already been reported as far north as Kansas and Maryland.
Scientists have been working to find a predator to slow the spread of fire ants. Some people think that armadillos will eat fire ants. Many homeowners have seen the results of armadillos digging in the lawn to find white grubs. These homeowners report that they would not like to have the armadillos come back, even if they were coming to eat fire ants.
Researchers have found a type of small fly (called a phorid fly) that can be a predator of fire ants. To start the process, the female fly deposits an egg on a fire ant worker. When the fly egg hatches, the maggot crawls inside the ant's head. As the maggot grows, it eats the ant from the inside. The ant' is killed in the process.
Researchers say that when the flies are active, they intimidate the fire ants. The fire ant workers refuse to leave the mound to forage for food. This causes stress and eventually starvation in the fire ant mound.
The phorid fly research has been underway for some time. There are still some technical issues that have not been resolved, so the flies are not ready to go to market as a fire ant control tool.
There are several species of parasitic nematodes that attack fire ants in the soil. There are mites that attack fire ants in their nest. These tiny animals can be hard to find. Some people say that they are difficult to use and provide inconsistent results.
In some areas of the country, there are other species of ants that compete with fire ants. In Southeast Texas, there is an ant that displaces fire ants. Homeowners who have experienced the new ant say they would prefer to have the fire ants back.
Until reliable predators can be found, many experts recommend controlling fire ants by drenching the visible mounds with liquid insecticide and broadcasting bait on the lawn.