Fly Release Is Latest Step in Fire Ant Biocontrol Strategy

GAINESVILLE, Fla., July 9--A Brazilian fly that dive-bombs fire ants will be released here today as part of a new, environmentally friendly strategy to use natural enemies to control the ants that now infest millions of acres in the southern United States.

Scientists with the Agricultural Research Service--the U.S. Department of Agriculture’s chief scientific agency--will release several thousand phorid flies and parasitized ants at Gainesville’s Kanapaha Gardens. Florida officials and USDA’s Animal and Plant Health Inspection Service have approved the release. The fly attacks only fire ants and poses no threat to any other insects, wildlife or humans.

Porter spent six months last year in Brazil studying the flies and fire ants in their native country. Known for their burning sting, fire ants are thought to have spread to the United States via contaminated ships from South America early in the 1930s. The ants now infest an estimated 278 million acres in 11 southern states and Puerto Rico. They have flourished in the United States because they have no natural enemies here.

Porter has been studying the parasitic flies under quarantine in Gainesville since 1994. The flies zero in on fire ants and pierce the pest’s outer cuticle, then deposit an egg inside the ant. The egg eventually develops into a larva inside the ant, moves into the ant’s head and causes the ant’s head to fall off. The fly completes its development inside the fallen head.

The fly is one of several biological controls for fire ants now under study at ARS’ Center for Medical, Agricultural and Veterinary Entomology in Gainesville, according to David Williams. He is the lead scientist on the center’s fire ant biological control research. Williams said two other possible biocontrols are:

• Thelohania solenopsae, a microsporidium discovered in Brazil in 1973. This organism infects fire ants with a slow-acting disease that chronically wastes and debilitates individual ants. The colony itself is weakened and eventually destroyed due to a lack of worker ants. In lab studies, Williams found that after 3 months, colonies infected with the microsporidium were smaller than healthy colonies.

• Solenopsis daguerrei, a parasitic ant discovered in Argentina in 1930. This parasitic ant queen uses her mandibles to clamp onto a fire ant queen’s body. “The parasitic ant is able to disguise herself from the fire ants; otherwise she’d be killed,” Williams said. “She may somehow mimic the natural sex attractant of the fire ant colony.” The fire ant queen becomes debilitated and lays fewer eggs, weakening the colony.

Porter and Williams said they’re optimistic that the release of phorid flies and other natural enemies will eventually tip the ecological balance against fire ants in the United States and reduce their high populations here.

Scientific contact: Sanford D. Porter, Imported Fire Ant and Household Insects Research Unit, Agricultural Research Service, USDA, Gainesville, Fla. 14565. Telephone: (352) 374-5914, fax (352) 374-5818 sdp@nervm.nerdc.ufl.edu.