Fly Release Is Latest Step
in Fire Ant Biocontrol Strategy
By Tara Weaver
July 8, 1997
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
Agricultures chief scientific agency--will release several thousand
phorid flies and parasitized ants at Gainesvilles
Kanapaha Gardens. Florida
officials and USDAs 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.
In these field tests, we want to demonstrate that these flies can help reduce
fire ant populations, said Sanford Porter, an ARS
entomologist in Gainesville. The flies are effective in our quarantine
laboratory, but we want to see how well they do in outdoor conditions.
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 pests outer
cuticle, then deposit an egg inside the ant. The egg eventually develops into a
larva inside the ant, moves into the ants head and causes the ants
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 centers 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
queens body. The parasitic ant is able to disguise herself from the
fire ants; otherwise shed 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 theyre 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,
Fire Ant and Household Insects Research Unit, Agricultural Research
Service, USDA, Gainesville, Fla. 14565. Telephone: (352) 374-5914, fax (352)