• Biologic Control of Fire Ants
Biologists have looked for natural predators to help control red ants. Biologists with the USDA working with entomology departments at a number of universities have imported, raised and released phorid flies, also known as decapitating flies, from South America. These tiny flies pursue the workers and lay eggs on the worker fire ant’s thorax. The eggs hatch into larvae that migrate to the ant’s head where they develop into adults, feeding on the head, which eventually falls off. The adult fly develops within the decapitated head. When it emerges, the attacks on ants continue. Each female fly may lay eggs on 200 to 300 fire ants.
The benefit of the decapitating flies is twofold. Besides killing ants, the tiny phorid flies are reportedly aggressive in their pursuit of fire ants, chasing the workers back to the mound and disrupting the ant’s foraging and thus the overall health of the mound.
Phorid flies have been released in most Southeastern states and are also increasing their range. In 2000, phorid flies were released in Lowndes County, Ala. and in Tift County, Ga. Overall, phorid flies have been released in 11 Southeast states and populations have been established in six states.
Decapitating flies aren’t considered a means to eradicate fire ants, but when used in combination with chemical agents, may lower populations.
A second biological effort is also underway to slow the fire ant’s efforts at conquering the South — the importation of fire-ant disease from South America.
Thelohania is a disease that afflicts fire ants in Brazil. In the South, biologists have used the disease to infect fire-ant mounds. Fire-ant larvae infected in the laboratory with thelohania are introduced into a fire-ant mound. The ants readily adopt the larvae and raise them, spreading the disease among the workers and to the queen.
• Chemical Treatment
Chemical treatment for fire ants fall into three categories: granular baits, mound treatments and broadcast insecticide.
Granular baits are scattered around fire-ant beds. The workers pick up the bait and carry it back to the mound. Interestingly, fire ants cannot eat solid food. When a worker finds food it brings it back to the mound where it is given to ant larvae. The mature larvae chew the food and convert the solid food into a liquid which is shared with other ants including the queen.
The dilemma for fire-ant bait manufacturers was to create a bait that was slow-acting enough so that it didn’t kill the worker that found it before it could deliver the bait to the mound. If the bait isn’t dispersed within the mound and doesn’t kill the queen, the colony is unaffected.
Mounds can also be treated by flooding them with insecticide, which kills the colony quickly. This treatment may be most effective around highly used areas around homes.
Broadcasting insecticide is an effective way to kill fire ants over a larger area, such as a pasture.
Any treatment that leaves the egg-laying queen alive is ineffective, which is why bait and insecticide manufacturers recommend you do not disturb the mound ahead of treatment. If the mound is disturbed, worker ants may lead the queen away through underground tunnels to a safe haven.
If you have heard of some home remedies to kill fire ants, the USDA says don’t bother. According to the agency website, things like scattering grits, uncooked rice or white potatoes on the mounds have no impact on fire ants. Pouring vinegar or baby powder on the mound is also ineffective. You may succeed in irritating the ants enough that the mound appears to go dead, but usually all that has happened is the ants have simply picked up and moved to a new site.
The use of gasoline is also not recommended, in part because of the potential danger to the person setting fire to the mound. Too, the soil within the mound insulates the mound from heat from a fire.
If you thought you had no use for an armadillo, consider this: armadillos are a fire-ant predator and actually dig the mounds to feed on the workers and larvae, oblivious to the stings.
Because fire ants recolonize an area, any treatment is considered control rather than eradication, and must be ongoing. Fire-ant baits such as Amdro®, Logic® or Award® will control ant populations but only with regular re-application.
While research on the impact of fire ants is ongoing, biologists all agree that fire ants continue to expand their range in North America, and they are here to stay.
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