A big ol' fire ant mound is an eyesore. But looking at one isn't nearly as
painful as stepping in it. Those white blisters are a lasting reminder of just
how nasty these pests can be.
While it would be nice if fire ants could be eradicated, or at least controlled
quickly and easily, that's rarely the case.
Fire ants have had a toehold in the South since they sneaked into Mobile, Ala.,
with a load of ballast in the 1930s. Since then they've spread all across the
Southeast. Some have even managed to jump the desert to southern California.
Cold temperatures and a lack of rainfall appear to be the only things stopping
fire ants from spreading across the whole country.
More than a nuisance, fire ants can be treacherous for livestock and pets. And
if you've got a lot of ground to cover, control can be time-consuming and
costly. But it has improved, and there are new control methods today, says David
Oi, a Gainesville, Florida-based USDA entomologist.
In many cases Oi says fire ant baits are still a good, cost-effective method of
control. Some bait products work in as little as a week. If you're dealing with
a few individual mounds, these baits are the way to go. If the infestation is
larger, broadcast the bait and time the application for when the ants are out
foraging for food.
"Baits don't last a long time so it is best if the ants feed on them within a
day," Oi says. "Apply them when the weather is nice enough for a picnic. Late
spring usually works well when it's warm and the rain brings them out. Plus, if
they've been through winter they're likely hungry."
Wayne Gardner has his own simple test to see if the time is right. This
University of Georgia entomologist uses the "highly complex" potato chip test.
"Place some potato chips out in the area to be treated. If ants come to that
food source, then apply the bait," he says.
Fire ant baits aren't the only controls available. There are promising
biological controls already at work and more on the way. Phorid flies, a
parasite that feeds on the ants, have been distributed by the USDA since 1997.
There are also pathogens Oi is researching that will attack the ants.
"These pathogens are very detrimental to fire ants," he explains. "They cause
the queens to shut down egg production and die. The pathogens are slow, though,
and don't spread like phorid flies."
For Lee Norman, controlling fire ants isn't just something he'd like to do; it's
a have-to situation. This Moultrie, Ga., turfgrass grower has 300 acres of
bermudagrass, centipede and zoysia. Fire ants can hurt his business, so he takes
a serious stand when it comes to control.
"Our customers would raise sand if the sod had fire ants in it," he says, adding
the grass is laid by hand, and fire ants would make that a painful job.
The pest also can make a mess of equipment—especially mowers. "We mow twice a
week in the summer down to a height of 5/8 to 3/4 inch. A fire ant mound would
wreak havoc on the reel mowers we use," says Norman.
Individually treating mounds isn't practical or economical for Norman, so he
uses fipronil (Chipco Choice) to do the job. It's labeled and effective against
fire ants, as well as mole crickets.
Fipronil is granular and has to be watered in or applied before a rain. "It has
residual effects and apparently stays in the upper 2 centimeters of the soil,"
Georgia entomologist Gardner adds. Maximum suppression occurs four to six weeks
following treatment, but control lasts all season long. The chemical cost per
acre runs around $200.
Norman says some years he follows up in late July to early August. In these
cases he may come back with carbaryl (Sevin) to control armyworms. This is also
labeled for fire ant control, so it does double duty.
See next page for more treatment options.
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Fly-by Assassins
Fire ants near you may soon find themselves at the mercy of the South American
phorid fly. These little ant torturers were discovered by USDA entomologist
Sanford Porter.
The phorid fly is the reason fire ants are five to 10 times more abundant here
than they are in South America. These minute insects inject their eggs into fire
ants. There they hatch, and the larvae migrate to the fire ant's head where they
feed.
"In two to three weeks the head pops off, slick as a whistle," says Porter.
"If you have sharp eyes and get close to a fire ant mound—a foot above—you can
see the little flies attacking the ants. They look like little attack
helicopters."
You're probably wondering what else phorid flies eat if they run out of fire
ants. The great news is: apparently nothing. "They are highly specific," says
Porter. "If they can't find fire ants they die."
But that's not too likely. "Phorid flies haven't eradicated fire ants in South
America," says Porter. "They won't eradicate them here either."
Since 1997 Porter and his colleagues have been releasing different strains of
phorid flies around the Southeast. They are now in Florida, Georgia, South
Carolina, Alabama, Mississippi and Tennessee—and still spreading.
So far, four species of phorid flies are working their magic on fire ants, and a
fifth is in quarantine. Porter says by this time next year it should be
released. "Each species is complementary. They attack different sizes of fire
ants."
These flies aren't raised commercially, adds the researcher. So you can't buy
them. But once released they spread on their own and the benefits are forever.
Try the Texas Two-step
While there is no one best approach to fire ant control, Texas A&M's Bart Drees
says he likes a method they call the "Texas two-step" in his area. Here's how it
goes:
STEP 1: BROADCAST A BAIT-TYPE PRODUCT. Start with the old standby, Amdro. "It
will usually accomplish 80 to 90% elimination of fire ant colonies in three to
six weeks," says Drees.
Amdro also gets the nod from University of Georgia entomologist Wayne Gardner.
"It was developed in the late '70s, is safe to use and not that expensive." In
retail stores, it runs $10 to $12 a pound.
If you're in a hurry, Drees recommends Advion or another of the indoxacarb
products. "It will eliminate ants in three to 10 days instead of three to six
weeks." Cost is higher, usually $20 a bag or $80 an acre.
Insect Growth Regulators also work, but slowly. They don't kill ants outright,
but keep them from reproducing. Colonies decline slowly; effects last for
months. Extinguish, or one of the methoprene-type products, is $8 to $10 a
pound, or $8 to $15 an acre.
There are also combination products—like Amdro Plus or Amdro FireStrike. These
combine Amdro and an IGR. "You get a fast response that lasts," says Drees. "It
will get 80 to 90% of the colonies and is applied at a low rate, so it is
economical." Drees says it averages around $10 an acre.
STEP 2: TREAT MOUNDS THE BAIT DIDN'T GET. Treatments can include anything from a
pot of hot water to a liquid or dust, like Sevin, Orthene or a pyrethroid
product containing permethrin, bifenthrin, cypermethrin, lambda-cylahothrin or
other ingredients.