TBO.com - TBO is Tampa Bay Online

War With Fire Ants Comes To A Head

U.S. Department of Agriculture

Loathed for their venomous, painful bite, fire ants have spread across much of the Southeast.

ADVERTISEMENT

By NEIL JOHNSON

The Tampa Tribune

Published: September 18, 2008

Related Links

• How It Works (.pdf)
• Video Of Flies Emerging

South American Phorid Fly

TAMPA - A flea-size fly imported from South America is killing fire ants in a way sure to please anyone ever bitten by the bugs: The ants' heads fall off.

"You almost feel sorry for the ants - then you get stung and get over it," said Sanford Porter, a research entomologist with the U.S. Department of Agriculture studying fire-ant controls.

Scientists have released thousands of tiny parasitic flies across the state since 1997 to battle fire ants throughout the South, where they have infested more than 300 million acres and ravaged gardens and farms. The agriculture department estimates fire ants cause $6 billion of damage annually in urban and rural areas.

The fly is a natural enemy of fire ants in their native South America and one reason fire ants make up perhaps 20 percent of ant colonies there compared with 80 percent in Florida, Porter said.

Working with the University of Florida, scientists with the agriculture department released the first fly species near Gainesville in 1997. Other releases followed in Fort Pierce, Sarasota, Naples and Kendall, near Miami.

The fly populations since have expanded to cover all of Florida except the western Panhandle. They can be found as far north as Savannah, Ga., Porter said.

To the fly, a fire ant is a six-legged nursery, a host to lay an egg in and for the offspring to feed on over a period of five weeks until the head pops off to serve as a cocoon.

But even with 200 eggs per fly and thousands of flies across the state, the flies can't decapitate enough ants to eradicate them.

They also harass the ants, however, hovering over their mounds like dive bombers and keeping them from venturing far for food. That opens up areas for native ants to forage for food.

"Hopefully, this will help tip the balance in favor of native ants," Porter said.

Though the flies are everywhere, they're seldom seen because they're so small.

Introducing one non-native species to combat another carries the risk of making things worse.

That's why scientists studied the flies for years before letting them loose on fire ants. They're confident the flies won't produce unintended consequences, in part because they have evolved to prey only on fire ants.

Part of the testing was to expose the flies to native ants. The flies ignored them.

The flies are released in two ways, usually 1,500 to 8,000 at a time.

•Scientists take a box of flies to a release site, kick over several fire ant mounds and release the flies.

•In a kind of Trojan horse method, scientists capture fire ants and bring them to a lab where the flies inject their eggs, then the infected ants are released back to the mounds.

It's hard to exaggerate the scourge fire ants present.

They disrupt natural ecosystems, eat young birds and amphibians, kill citrus trees and even short out well pumps and other equipment because they're attracted by electric current.

Fire ants came to the United States in the 1930s or earlier and now infest the entire South, although they have reached as far as California.

By introducing more species of the flies, along with other parasites such as a fungus, scientists hope to reduce the fire ant population to levels found in their native South America.

"When you go to South America for research, you really have to look to find fire ants," Porter said.

Reporter Neil Johnson can be reached at (813) 259-7731 or njohnson@tampatrib

.com.

Share this:

Loading Comments...

Email Print

ADVERTISEMENT