Fire Ants Haven’t Spread Past One Lawrence Block ... Probably 6/21/01

MANHATTAN, Kan. – When the testy little stingers known as red imported fire ants show up in Kansas, the state’s entomologists get a little antsy, too.

The latest invasion in southwest Lawrence has been particularly worrisome. It’s different. And no one can predict what the differences may mean for Lawrence or other areas of urban Kansas.

The fire ants weren’t discovered until late last fall. Children at play reported repeated stings that burned, itched and caused second-day white blisters.

Local pest controllers took care of the colony living in the family’s raised flower bed. But, suspecting the ants were unusual, they took steps that involved a University of Kansas entomology professor ... who called Douglas County’s K-State Research and Extension office ... who notified the Kansas Department of Agriculture (KDA) – the agency with regulatory authority for introduced and quarantined pests.

County Agents Fielding Questions
To Help Residents Identify Fire Ants

LAWRENCE, Kan. – Worried about whether the tiny workers around their home might be the dreaded red imported fire ant, Lawrence residents have been flooding Douglas County’s K-State Research and Extension office with phone calls.

So, horticulture agent Bruce Chladny and ag agent Bill Wood have developed a list of questions that can help homeowners know whether to sigh with relief or investigate further:

Is it big? If so, it isn’t a fire ant.

Is it black? If so, it’s probably a carpenter ant – which is worth watching, but often isn’t a serious problem because carpenter ants chew into wood to build a home. They don’t eat it as termites do.

Is it really, really small? A "yes" answer points to one of several native ant species, because imported red fire ants are a medium size – one-sixteenth to just under one-quarter of an inch long.

Is it red in front and a red-brown to black in back? Homeowners often can’t answer this question too accurately, when describing an insect that’s one-sixteenth of an inch long. But the two-toned color combination is a characteristic that fire ants share with some native species.

Does it have a heart-shaped tail segment, when viewed from above? If so, it’s a native.

Is it aggressive? Native imported red fire ants will boil out of a colony to attack and sting. Other ant species can sting, too, but somehow don’t approach the task so wholeheartedly.

If the answers to these questions still leave room for doubt, the agents suggest that residents collect a half dozen ants, preserve them in a small bottle of rubbing alcohol, and bring them to the Research-Extension office for forwarding to Kansas State University’s diagnostic lab.

On their own, homeowners have no chance of identifying the species other than by its blister-producing sting, its ability to bite and sting repeatedly, and its tendency to attack anything that disturbs the ants’ work or home, said K-State entomologist Leroy Brooks.

"Fire ants have two little nodes in the middle, where most ants have one. But homeowners couldn’t see that, even with a hand lens," he said. "The curvature of their thorax also is different from that found on several of the Kansas ant species they resemble. But even this difference is so subtle that you need several samples and a microscope to make a judgment."

KDA entomologists were on-site immediately and then went back to Lawrence early this spring. They fully expected to find no problem. Scientists with computer models have projected that fire ants’ ability to survive Kansas wintertime temperatures is "highly unlikely."

But the entomologists discovered fire ants had indeed made it through the harshest winter in recent state history. In fact, the pests were well established and in the process of spreading into neighbors’ yards.

During April, the entomologists discovered and destroyed several colonies. Then, after a 2-inch rain, they found about a dozen more.

They now have eliminated 19 colonies, scattered over one-third of the 16-acre subdivision. Plus, they’re frequently baiting the area with small, peanut oil-soaked cardboard tags, to survey for any new or previously undetected colonies.

The size of the infestation suggests fire ants had been in the neighborhood for at least two to three years, said Stephan White, entomologist with KDA’s Plant Protection and Weed Control Program.

"If the ants had gone unnoticed another year, the problem could have been pretty devastating. So far, though, they seem confined to one square block. They haven’t crossed a street," he said.

Lawrence residents have been taking the problem seriously. Horticulturist Bruce Chladny said the county’s Research-Extension office has been flooded with phone calls, as well as bagged and jarred samples to mail to Kansas State University’s Insect Diagnostic Lab.

The imported red fire ant first arrived in the United States in a 1930s shipment from South America to Mobile, Ala. The ship used soil as ballast, and experts believe the ants were in that dirt.

The pest has spread across the South and into parts of Texas, southern Oklahoma and California. "Past efforts to eradicate established fire ant infestations in the South have been disappointing – or perhaps ‘failed’ is a better word," said K-State entomologist Leroy Brooks. "This species has a complex life history that can make completely getting rid of it hard to achieve."

Fortunately, the map tracing fire ants’ national invasion hasn’t changed much since 1988, White said. It now includes California, but neither New Mexico nor Arizona. (Fire ants once tried to move into Arizona, but that infestation got eradicated.) And, the ants’ habitat zone still is at least one-half of a state away from Kansas – suggesting the pests can’t thrive in hot, dry climates or ones that get fairly cold.

But fire ants have made it as far north as isolated sites in Oklahoma City, Tulsa and Stillwater. Evidently, the species can sometimes survive outside its normal habitat if it connects with the protection and warmth available in populated areas, Brooks warned.

White thinks Kansas’ latest invasion survived the winter by nesting under the warm slab foundations typical of homes in the Lawrence neighborhood.

That’s one reason why KDA’s entomologists are being so careful now and why Brooks has prepared factsheets on how to recognize fire ants and take an ant sample.

Another reason is that fire ants don’t necessarily follow the typical colony "rules" that every school child learns about in science class. When fire ants get overcrowded, they can produce winged queens that fly off to mate and start a new colony some distance from the original one. But, a genetic change now also allows fire ants to have multiple queens in the same colony.

"When these polygyne colonies begin to get crowded, one or more of the new queens just move over a ways in the soil and start a new family – a process called budding. Because this all happens underground, you can’t see how far the extended colony goes. So, it’s much harder than a single-queen setup to destroy completely," Brooks said.

"Lawrence’s infestation appears to have spread by the budding process," White said. "That may be why we can’t find any colonies that have crossed the street."

KDA’s entomologists practically lived there for almost a month and still make weekly visits. They think they’ve found and treated all of the "budded" nests, but plan to keep checking until they know the record-setting infestation is history.

Typically, winged fire ant queens aren’t a threat in Kansas because they can’t make it from Tulsa or Stillwater on their own, Brooks said.

Still, fire ants can be transported in soil. Several years ago, an infestation in a Newton, Kan., home landscape traced back to potted plants purchased in Texas. A 1999 infestation in a Pittsburg, Kan., nursery came with plant shipments that contained Texas imported red fire ants. A more recent case in Olathe, Kan., arrived with plants shipped from Florida.

But, someone could spread the pest by moving from the South to Kansas and bringing along a philodendron that had spent the summer on a patio, White said.

"The ants could be carried along with the soil clinging to earth-moving equipment that’s brought into Kansas from an infested area," Brooks said.

Or -- what neither entomologist mentions out loud -- the Lawrence infestation also may have produced mated, winged queens over the past few years -- queens that flew some distance away and established now-undetected new colonies. The stinging ants may have traveled in soil that left the neighborhood with a transferred Lawrence employee or graduated KU student who kept houseplants outdoors last summer.

"The KDA has demonstrated its determination to eradicate serious pest problems such as this while there’s still a chance to do so. Often, once a pest gets firmly established, this is no longer an option," Brooks said. "The KDA can’t do it alone, however. Kansans need to be aware of the risks and stay alert for any signs of unusual insect activity."

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.