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No 'Magic Bullet' for Fire Ants, UGA Expert Says

A few phorid flies in Florida will have Georgians cheering them on in their natural work, chopping off fire ants' heads.

But don't get too excited.

"The fact that it's a biological control agent indicates this fly won't totally eliminate fire ants," said Beverly Sparks, a University of Georgia entomologist.

The U.S. Department of Agriculture released some Brazilian phorid flies July 9 to begin field tests near its Gainesville, Fla., lab. But Sparks said biological control agents won't banish fire ants from U.S. soil.

"We tend to think of fire ants in terms of eradication," Sparks said. "Phorid flies and other biological controls will stress colonies. They'll suppress them. But they won't totally get rid of them."

Sparks, a research and extension scientist in the UGA College of Agricultural and Environmental Sciences, focuses her own research on controlling fire ant populations.

"We're developing control programs," she said. "We're studying learning how to best use the control programs we already have. And we're finding more environmentally friendly ways to control fire ants."

The technology to eliminate fire ants hasn't arrived, she said. But for most people, controlling them is another matter.

"We know how to control fire ants and do it economically in urban settings," Sparks said. "We haven't found an affordable way to control them in open rural areas, such as pastures."

With current products, effective fire ant control costs $20 to $25 per acre per year, she said. In home lawns, school yards and recreational fields, that's reasonable.

Sparks' research shows the best fire ant control is a simple two-step process. "Broadcasting a bait twice a year will reduce fire ant populations by 90 percent," she said. "Then supplement the bait by treating problem mounds that survive with a contact pesticide."

But zapping fire ants is an every-year commitment. "If you treat them only one year," she said, "you'll be worse off than if you didn't treat them at all."

Fire ants compete intensely with each other, she explained. Untreated, their population will level off at 20 to 40 mounds per acre.

"If you get rid of them one year and don't treat the next," she said, "they'll be the first things to come back. But they'll become established in higher numbers, because they won't have larger mounds to compete with. Instead of 20 to 40 mounds, you'll have hundreds."

Having to treat fire ants year after year is far too costly to be practical in farm-size areas.

"We can get them out and keep them at levels that are acceptable in urban settings," Sparks said. "But if you have 300-400 acres of pastures, it's no longer cost-effective."

So scientists look for new ways to control them. Another UGA researcher, Ken Ross, is studying fire ant genetics.

Specifically, Ross is trying to find why fire ants go from single-queen to multiple-queen colonies. In the latter, worker ants sometimes destroy egg-laying queens. If he can find the genetic trigger that causes that, he may be able to cause single-queen mounds, in effect, to commit suicide.

The prospect is fascinating, as is the ant-beheading phorid fly. The tiny fly lays its egg inside a fire ant's body. The egg hatches into a larva, which moves into the ant's head and causes it to fall off. The fly completes its development inside the fallen head.

But don't expect the tiny flies to decapitate Georgia fire ants soon.

"I don't anticipate that phorid flies will be released in Georgia for fire ant control until scientists at the Gainesville laboratory have studied them for many years," Sparks said.

Scientists are working on other biological controls, too. For now, though, everything they know about killing fire ants won't get rid of them. "All we can do now is control them," Sparks said.

(Dan Rahn is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)

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