ALABAMA A&M and AUBURN UNIVERSITIES

Scientists Enlist Old Foe To Fight Fire Ants

AUBURN, SEPT. 10---In the 70-year battle against fire ants in the Southeast, scientists have thrown in everything but the kitchen sink. Now it appears an ancient enemy of the ants – a tiny insect known as the phorid fly -- may provide the best control yet.

Native to South America, fire ants have been a bane for Southerners ever since they jumped ship in Mobile Bay and spread throughout the region.

The newcomers easily wrested away woodlands and lawns from native ant species throughout the South. Their large, unsightly mounds now are as common a feature in Dixie as kudzu and cotton bolls.

"Once the ants spread from Mobile Bay there were no natural predators to stop them," says Dr. Kathy Flanders, an entomologist with Alabama Cooperative Extension System. "As a result, they were able to out compete all other native ant species, all of which were handicapped by predators and parasites."

Pesticides are only marginally effective on the ant. Treated areas are rid of the pests only a few months before fire ant queens, known as reproductives, fly in, burrow into the ground and begin establishing mounds again.

What the Southeast needed was a natural enemy of the fire ants – something that could keep fire ant numbers downs.

That’s precisely the idea U.S. Department of Agriculture researcher Sanford Porter had when he traveled to South America several years ago to study the habits of one of the fiercest enemies of the fire ant: the tiny phorid fly.

After closely studying the flies and mastering their reproductive habits, Porter obtained permission to bring some of the flies back to the United States for closer study. Since then, he’s worked with Flanders at Auburn University and with Extension specialists and researchers at other Southeastern universities to determine if the flies are well suited to conditions in the Southeast.

In South America, the tiny insects have earned the nickname "decapitating flies" – and for good reason, Flanders says.

"After a fly lays her eggs on a fire ant, the emerging larva makes its way into the ant’s head," she says. "It then proceeds to eat out the inside of the head. Eventually the head falls off and out emerges a new fly."

As the new generation emerges, the cycle of egg laying and decapitation begins again.

Although phorid flies carefully patrol the ant’s forage trails and tend to attack in groups, only about 1 percent of all fire ants exposed to these predators actually fall victim to this cruel fate. In most cases, the ants are just too terrified of the flies to leave the mound, and the result is less foraging and, therefore, fewer ants.

"In South America, phorid flies and other predators keep fire ant numbers down significantly," Flanders says. "There are only 15 or 20 percent as many mounds and foraging ants as there are here."

"What people have to realize is that we won’t manage to wipe out the ants entirely with these predators," she adds. "If we can get down to 30 percent or even half of the fire ants we have now, that would be progress."

Even while Flanders and other experts are excited about the presence of the phorid flies, they urge caution.

While the flies seem to be doing well in a research area near Notasulga in Southeast Alabama, a similar release of the insects near Talladega in Central Alabama didn’t survive.

"That’s what we really don’t know at this point," says Lawrence "Fudd" Graham, coordinator of Auburn University’s fire ant control project. "We’ve got to determine how far north the flies survive as well as the kind of habitat in which they will be most likely to thrive, whether it’s a woody area or an pastureland setting."

Despite the unusually hot, dry summer, the flies introduced near Notasulga seem to be thriving.

"If they over-winter into next year, we expect them to emerge and spread throughout these woods," Graham says.

They end result may be significantly fewer fire ants throughout the Southeast.

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SOURCE: Dr. Kathy Flanders, Extension entomologist, Alabama Cooperative Extension System, (334) 844-6393.