As if red imported fire ants weren’t enough to cause havoc across Georgia, now these pests have some company, according to Sharon Omahen, news editor, University of Georgia College of Agriculture and Environmental Sciences, Athens, Ga.
A new hybrid fire ant – a cross between the red and the black imported fire ant – can now be found across northern Georgia. These northern counties were free of fire ants until 1985 when a county extension agent in Rome, Ga., reported finding them. 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, entomologist, University of Georgia College of Agricultural & Environmental Sciences. “At first they thought the ants were red imported fire ants, 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, Gardner said. “The hybrids are almost totally black, so they look more like the black imported fire ants,” he explained. “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 survive in the colder areas of the state? “Sharp changes in temperature really tell a tale on fire ants,” Gardner said. “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.”
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.”
And if you ask Gardner which ant is worse – the hybrid or the red – he said: “Both forms are bothersome, but, so far, the black is restricted in its range, and the red is far more aggressive. But to homeowners, it really doesn’t matter. They just want them all dead.”
The author is managing editor of Lawn & Landscape magazine and can be reached at nwisniewski@lawnandlandscape.com.