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.”
