Red imported fire ants aren't the only fire ants causing havoc across Georgia. Now they've got company.
A new hybrid fire ant, a cross between the red and the black imported fire ant, can now be found across northern Georgia.
Georgia's northern counties were free of fire ants until 1985 when the county Extension agent in Rome, Ga. reported finding fire ants in his county. Researchers first thought these were black imported fire ants that had traveled from northern Mississippi where they thrive.
"We collected a sample of those ants and took them to the (U.S. Department of Agriculture) laboratory in Gainesville, Fla., to be identified," said Wayne Gardner, an entomologist with the University of Georgia College of Agricultural and Environmental Sciences.
They Look Alike
"At first they thought the ants were red imported fire ants," Gardner said. "But after a chemical analysis, they discovered they were actually this new hybrid."
To the untrained eye, the ants look very much alike. They're so similar, in fact, that scientists have to use laboratory techniques to tell them apart.
"The hybrids are almost totally black, so they look more like the black imported fire ants," Gardner said. "But the soil in the area actually dictates the color of the ants. In sandy soils they look lighter, and in clay soils they look darker."
UGA entomologists have compared the hybrid and the red imported fire ant and found they're tolerant to the same temperatures.
"They both survive the same length of time in cold temperatures, and they can both be controlled by the same pesticides," Gardner said.
So why do the black ants seem to survive in the colder areas of the state?
How Are They Different?
"Sharp changes in temperature really tell a tale on fire ants," said Gardner. "The hybrid forms may have adapted some sort of behavior that allows them to survive when the temperature drops. Or they may travel further underground than the red ants. We just don't know yet."
UGA entomologists are continuing to study the ants' differences and similarities. This summer they plan to study the effectiveness of biological control methods on the hybrid fire ant.
"We have released a parasite in south Georgia to fight the red imported fire ants, and we know it works," Gardner said. "Now we plan to release a new parasite against the hybrid and see how effective it is."
Gardner's research coordinator, Stan Diffie, has collected fire ants across the state and had them analyzed.
"Prior to 1980, Interstate 20 was thought to be the northernmost boundary for fire ants in Georgia," Gardner said. "Then fire ants began to appear in areas north of I-20."
All Georgia Counties Infested
UGA entomologists' surveys show that the hybrid fire ant really invaded the state from Alabama. They moved into the northwestern part of Georgia. Now all 159 Georgia counties report fire ant infestations.
"Their invasion certainly helped the fire ant to cover our entire state very rapidly," Gardner said. "We have found that Interstate 85 serves as a kind of imaginary boundary between the hybrid and the red imported fire ant. South of I-85, all the ants are red, and north and west of I-85, all the ants are hybrid ants."
So which one's worse, the hybrids or the reds?
"Both forms are bothersome, but, so far, the black is restricted in its range, and the red is far more aggressive," Gardner said. "But to homeowners, it really doesn't matter. They just want them all dead."
(Sharon Omahen is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)