Invaders from South America, non-native red fire ants have no natural enemies in the U.S. and have overtaken nearly the entire southeast. In Texas alone, they cost an estimated $1.2 billion a year in damage and chemical control. Researchers at The University of Texas, Texas A&M, state agencies, and the US Department of Agriculture are working on finding methods of natural, self-sustaining bio-control. One of the most promising methods appears to be a species of fly that uses ants as a larval host. Presence of the flies limits foraging by the ants, reducing the size and number of colonies. The host-specific flies have been released in Texas and spread over much of the ant's range.
In the meantime, there are a few methods that work for controlling fire ants, said Wizzie Brown, extension program specialist with Texas AgriLife Extension Service, in an interview. There are also a lot of home remedies out there that don't work, she said. (See Brown's blog on urban pest management here.)
Amdro Ant Bait
Ants carry the bait back to the colony and share it, killing the mound. Brown said it is important to use fresh bait, to apply it while ants are foraging, and when no rain is forecast. Wait at least 12 hours before watering. If surrounding neighbors all bait their yards at the same time, this helps prevent new mounds moving in once treated ones have died. Be sure to bait around the mounds of invasive, not native ants (see below for how to tell the difference). This method can be quite expensive.
Boiling water
This works, but boiling water kills only the ants it comes in contact with. Wait until after a rain, when more ants are above ground, and start at the edge, working in toward the center. Brown says boiling water poured on a mostly above-ground mound may kill up to 60 percent of the ants. The hot water will kill nearby plants.
Orange Oil
Made from d-limonene from orange oil extract, this pesticide kills ants on contact. Again, Brown said, it works best when the mound is built up above ground, typically after a rain. Apply from the outside of a mound inward, and follow package directions.
What doesn't work
Club soda poured on a mound does not kill ants, Brown says. It would take very high concentrations of CO2 to do so. The soda does not drown the ants, either, as some people think, because ant mounds are too extensive to become completely saturated. Pouring things on an ant mound can cause the ants to move, which is called displacement.
Grits also do not work. Fire ants can't eat solid food like grits, they only sip liquids (in fact, they only suck the soybean oil off ant baits), so despite urban legends, they don't eat grits and then explode. Grits can also cause displacement -- the ants don't leave, they just move. Chances are, their new mound will not be far away and you'll be no better off.
Native or Invader
Native fire ants help check the spread of invasive ones, so its best to leave native ants alone. Invasive ants build numerous, conspicuous mounds of loose soil above ground. The workers vary in size but all have the same body proportions, and the head width never exceeds the abdomen width. Large, native worker ants, by contrast, have heads wider than their abdomen. Also, native species are a uniform color, while invasives have an abdomen darker than the rest of the body.
Do not use broadcast pesticides in an attempt to control invasive fire ants. These chemicals indiscriminately kill everything, including beneficial insects. Also, killing native ants simply leaves a vacuum, making it easier for invasive ants to move in.
Melissa Gaskill - An independent journalist for 16 years, Melissa Gaskill holds degrees in biology and journalism and writes about travel, nature, outdoor ...
