Rep. Chip Limehouse of S.C. House District 110 (L) and Clemson Extension Agent Tim Davis (R) watch Red Imported Fire Ants react to phorid flies released at Boon Hall near Charleston on Oct. 7

DATE: 10/24/2005

CONTACT: Tim Davis, (803) 635-4722

F. Brian Smith, (843) 722-5940

WRITER: Tom Lollis, (803) 284-3343, ext. 241

Long-term goal is S.C. fire ant densities more like Argentina’s

CHARLESTON – Tim Davis would like to see a fire ant population in South Carolina that is more like Argentina’s.

“Densities here are five to seven times greater than what they are in South America, where the ants come from,” said Davis, Clemson Extension county agent and specialist for the Areawide Imported Fire Ant Program.

Why? The Red Imported Fire Ants (RIFA) left behind their natural enemies -- diseases, parasites and predators -- when they were accidentally brought to this country in the 1930s. Since then they have spread with impunity until they now occupy 390 million acres in 13 states and Puerto Rico.

As part of a cooperative effort with USDA-ARS and other Southeastern states to reunite the ants and their enemies, Davis began a 10-day release of one of the predators at Boone Hall Plantation on Oct. 7. Pseudacteon tricuspis is a tiny phorid fly which lays eggs in non-native fire ants.

“The eggs become larvae that live inside the ants’ heads, eventually killing them,” said Davis. “The first release of phorids was at Clemson in 1998. We’ve also released tricuspis at Pelzer and in the counties of Fairfield, Richland, Williamsburg, Horry and Charleston.”

A second species, P. curvatus, became available for release in 2003. It has been released in Fairfield and Charleston counties. Curvatus was also released this year near Greeleyville in Williamsburg County.

Two more species are in the pipeline for delivery from the USDA-APHIS rearing laboratory in Gainesville, Fla.

Flies have also been established at McIntire Air National Guard Base and at Fort Jackson near Columbia, as well as near Greeleyville.

“Our plan is to let the flies spread naturally from strategic locations around the state,” said Davis. If everything works perfectly, the flies could blanket the state completely in 10 to 15 years, just like the RIFA.

“It could be faster or slower, depending on the species, failures at release sites, freak weather or other unforeseen events,” said Davis.

He is encouraged by signs that the fly is spreading. Flies have been found seven miles from a release point in Fairfield County in just two years.

Rep. Chip Limehouse of S.C. House District 110 was on hand at Boone Hall to watch the process.

“I’m very impressed,” he said. “If this works, it could be one of the silver bullets we’ve been looking for to deal with the terrible fire ant problem we have in South Carolina.”

Biological controls such as phorid flies and diseases caused by a protozoan called Thelohania solenopsae can significantly reduce RIFA populations once they are strongly established.

Biology alone won’t be enough to control fire ants completely, according to Davis. A combination of fire ant baits and other chemicals, plus biological controls, will be needed to reduce populations to more manageable levels.

Other countries have similar problems with RIFA. The Clemson University fire ant effort has helped educate officials from Austrailia, Taiwan and China. Davis has made a presentation at a symposium in Taiwan and hosted a group from that country at the Sandhill Research and Education Center.

Davis said that fewer RIFA should help South Carolina’s native ants better compete for territory. Sheer numbers are a handicap for now. A strong native ant colony may contain 2,000-3,000 ants. A strong fire ant mount can contain several hundred thousand.

“In South America a heavy infestation is 20-30 mounds per acre. We have places in South Carolina with as many as 600 mounds per acre,” he said.

A 1998 survey indicated that 33,000 South Carolinians sought medical treatment for RIFA stings. Fifteen percent of the population have severe allergic reactions and as much as 2 percent have potentially fatal reactions. Dealing with RIFA costs the average household about $86 a year, or $124.7 million for the entire state.

Lower RIFA populations will also benefit South Carolina wildlife. RIFA affect species such as quail, the loggerhead turtle and the gopher tortoise, an endangered species.

“The ants go after young turtles as they are hatching and even attack adult turtles as they try to lay eggs,” said Davis.

For more information about managing fire ants in South Carolina, a fact sheet is available at: entweb.clemson.edu/cuentres/eiis/newimp/newimp.htm. For more information about the Areawide Imported Fire Ant Suppression Program visit the USDA website at: fireant.ifas.ufl.edu/.

END