New Fly Species Could Make Memorial Day Picnics More Enjoyable

Ed Hunter (352) 392-1773 x 278

Sanford Porter, (352) 374-5914

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GAINESVILLE, Fla. — Memorial Day wouldn’t quite be the same without picnics, backyard barbecues and, of course, the ever-present imported fire ant, but a tiny new fly may pull up the welcome mat on the uninvited holiday guest.

In addition to a species of phorid fly they have been releasing since 1997, University of Florida and U.S. Department of Agriculture researchers now are releasing a second variety to target smaller fire ants. The objective: to broaden the successful offensive established with the original release, said Sanford Porter, a UF and USDA entomologist.

“We have two kinds of flies, one that attacks little fire ants and one that attacks big fire ants,” said Porter, an assistant professor with UF’s Institute of Food and Agricultural Sciences. “We’re hoping that releasing both species of flies will have a bigger impact on fire ant populations.”

The female phorid fly swoops down on an anthill and injects its eggs into the ants. When an egg hatches, the larval fly moves into the ant’s head, where it grows into an adult fly, causing the ant’s head to fall off in the process.

The fly is a natural parasite of the fire ant in South America but was left behind when the ants were accidentally imported to the United States 60 years ago, Porter said.

“Fire ants are not very common in South America,” Porter said. “But here in the United States they are five times as abundant and we think that’s because they have escaped their natural control agents like these phorid flies.”

Lloyd Morrison, a postdoctoral associate and USDA research entomologist, said the tiny flies will reduce but not eliminate fire ant populations.

“We know phorid flies cause fire ants to decrease their foraging,” Morrison said. “This gives other ant species a competitive advantage, so we hope native ant populations will increase and fire ant populations will decrease.

“But it won’t happen overnight,” he said. “It will take months, and perhaps years, until a new equilibrium of these ant populations is reached.”

Researchers have been releasing the larger phorid fly for four years at several sites in the Southeast. Within five years, Morrison said nearly 80 percent of the area that has imported fire ants also will have populations of phorid flies.

Morrison said the nearly invisible flies pose no threat to humans or animals.

“We’ve done extensive testing of these fly species to see if they attack any other species of ants, other organisms or whether they would be attracted to people or food,” Morrison said. “We have found that they are not attracted to anything other than ants and in fact are very specific to fire ants.”

According to Porter, the tiny phorid flies offer the hope of a natural alternative to commercial pesticides.

“Fire ants are found everywhere in the Southeast,” Porter said. “The problem is that the imported fire ants are running out a lot of our native species, which creates problems for agriculture, people’s health and the environment.

“The only real hope we have of wide-scale, permanent fire ant control are classic biocontrol agents like these flies,” he said.



Posted: May 23, 2001

Category: UF/IFAS

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