Red imported fire ants had no natural enemy in Red River County until this fall when phorid flies were released in the area to help combat the infamous pests.
Texas Cooperative Extension experts said they hope a population of the phorid flies will establish themselves by spring in a pasture near Clarksville, where the flies are likely to flourish and stalk fire ants.
"The flies as a biological control hold promise for suppressing red imported fire ants," said Extension agent Lynn Golden, based in Clarksville. "It doesn't promise to eradicate the ants. It's just another way to help control them."
The phorid flies were released on 24 mounds in late October, said Kim Schofield, an Extension program specialist in Dallas who coordinated the project. She and Golden will return to the mounds in April and October to measure the fly populations.
"We're hoping that the flies establish themselves as they have at other sites in the Dallas area and around the state," Schofield said. "We want to see fire ant numbers fall and native ants reclaim their territory."
The Clarksville project is Extension's latest and northernmost release of phorid flies in a long-running battle against fire ants in the state, said Dr. Bart Drees, a Texas A&M University professor and Extension entomologist.
"In the late 1990s, researchers began to see these as potential biological control agents," said Drees, who is based in College Station. "And since that time the flies have been imported to the United States, mass-produced and released."
Test releases began in 1997 to determine whether the flies would populate designated areas and to make sure they posed no threat to anything other than fire ants, he said.
In 2000, a governmental initiative brought several agencies together to raise and release large quantities of phorid flies in southern states, Drees said. The program involves Extension, the University of Texas at Austin, U.S. Department of Agriculture's Agricultural Research Service, the USDA's Animal and Plant Health Inspection Service and the Florida Department of Agriculture and Consumer Services.
Phorid fly populations have been established in Bastrop, Brazoria, Burleson, Cameron, Denton, Kenedy, Kerr, Lamar, Orange, Polk, Travis, Walker and Wharton counties, he said.
"I would say several dozen release sites have been established across Texas using two fly species, but many attempts failed," Drees said. "Over the coming years, established flies are expected to spread throughout the entire fire ant infested portions of Texas."
But it may take several years before the flies to become abundant enough to provide measurable effectiveness against fire ants, he said.
Red imported fire ants are native to South America and arrived in the U.S. in the 1930s aboard ships in Mobile, Ala., according to the Texas Imported Fire Ant Research and Management Project. They spread to southern states, arriving in Texas in the 1950s.
In Texas, they cost $1.2 billion annually in agricultural losses, ecological damage and pesticide expenses, according to Texas A&M's fire ant economics Web site, http://fireantecon.tamu.edu . Their sting makes them dangerous to humans, livestock, pets and wildlife.
In South America, phorid flies and other predators keep red imported fire ants in check, Schofield said. The female flies attack the ants and lay eggs in their bodies. Larvae eventually hatch and burrow into the ants' heads. There, they grow and release enzymes that cause the heads to fall off. Mature flies eventually emerge from the decapitated heads, and the cycle starts over.
"The flies attack and eventually kill the ants, but their real impact is that they stalk the fire ants when they're foraging," Schofield said. "That reduces foraging activity which, in turn, helps limit food within the fire ant colony."
Though fire ants have earned scorn, Drees cautioned, the war against them shouldn't extend to the nearly 300 ant species that are native to Texas.
Collectively, ants are regarded as beneficial organisms in the environment, he said. They prey on flea larvae, cockroach eggs and other pests. They aerate the soil and reduce compaction.
"Many of our native ant species are much more polite than fire ants," Drees said. "They nest in little out of the way areas. They don't sting. They do the good things without bringing to the table what fire ants do."
For more information on fire ants in Texas, go to http://fireant.tamu.edu.