Heads to roll as gov’t fights fire ants with decapitating flies

Heads will roll as a U.S. Department of Agriculture plan to control imported fire ants is put into practice this month in Florida. The plan introduces tiny South American phorid flies to the United States to control the pesky ants, whose spread has been unaffected by poisons and other measures. Phorid flies use the decapitated heads of imported fire ants to reproduce. “This is the only way we’re ever going to see a reduction in the number of fire ants in North America,” said one official associated with the plan.From the U.S. Department of Agriculture :UF RESEARCH PROVIDES HEAD START FOR CONTROLLING FIRE ANTS

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SARASOTA, Fla. — Heads will roll as a U.S. Department of Agriculture plan to control imported fire ants is put into practice this month in Florida.

The plan – based on research by Sanford Porter, a University of Florida Institute of Food and Agricultural Sciences adjunct professor employed by the USDA – introduces tiny South American phorid flies to the United States to control the pesky ants, whose spread has been unaffected by poisons and other measures.

Phorid flies use the decapitated heads of imported fire ants to reproduce.

“This is the only way we’re ever going to see a reduction in the number of fire ants in North America,” said Fred Santana, the integrated pest management coordinator for the UF/IFAS Sarasota County Extension Service.

Santana will be the first under the USDA plan to release the flies to Florida. The USDA funds the Florida Department of Agriculture and Consumer Services’ Division of Plant Industry to produce and distribute the flies.

“I had thought maybe you could just release the flies into the environment, but you have to go to great pains to make sure that the flies attack the ants,” Santana said.

After the flies are incubated, Santana will remove selected fire ants from their nests and place them in a flat-bottomed “attack box” that is about 35 inches long and 17 inches wide. Agitating the ants to ensure they don’t adopt defensive postures, he will release 40 to 60 flies into the box. After two hours, Santana will return the newly infected ants to their nests.

Santana said imported fire ants, which accidentally were introduced to Florida from South America 70 years ago and differ from a less-common native species, have a major impact in his area. The ants are capable of multiple stings and inject venom that raises white pustules.

“The ants cost millions in crop, equipment and livestock loss, and millions to control them,” Santana said. “They’re problems in playgrounds, parks, golf courses, pastures, lawns around houses, edges of sidewalks and just about any disturbed area.”

Santana said previous efforts to control the ants have been unsuccessful.

“We’ve been trying to kill these ants for more than 50 years, but their range just keeps expanding,” he said. “There are lots of poisons out there to kill them, but where you broadcast a poison which kills on contact or by ingestion, you also kill many nontarget ants and other beneficial insects.”

Unlike poison, Porter said his research has shown the flies are safe to people, animals and crops.

“It’s possible they might attack ants other than imported fire ants, but after extensive testing we’ve never been able to get them to do it,” said Porter, an entomologist for the USDA’s Agricultural Research Service.

Porter, who has been releasing phorid flies in north Florida for about four years, was the first to describe the fly’s life cycle in 1994.

“The flies hover above the ants, dive in, latch on to the ant’s body and inject their eggs,” he said. “The egg hatches, and a maggot wiggles its way into the ant’s head, where it grows for two to three weeks before secreting a chemical that dissolves the membranes holding the ant’s body together. In a few hours the ant’s head falls off. The maggot eats everything in it, then uses it as a pupae case — kind of like a cocoon.”

The density of imported fire ants in Florida is five to seven times that of its native South America, Porter said. He attributes this to changes in behavior the ants display in the presence of the phorid flies.

“The flies will hover above ants like little squadrons of Apache attack helicopters, dive in and hit ant after ant. Needless to say, the ants don’t like it,” Porter said. “They’ll run and hide if they can, and if they can’t hide they’ll curl into a defensive, upside-down ‘C’ posture.”

The ants have spread to many southern states, and a federal quarantine designed to limit their range regulates the distribution of agricultural products throughout the Southeast and in many parts of Texas. The USDA’s Animal and Plant Health Inspection Service is releasing phorid flies in all of the areas under quarantine.

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