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Flies being used to combat invasive red fire ant in Arkansas

Although not a native species, the red fire ant has been able to thrive in the southern United States primarily due to its lack of a natural predator. (Photo: KATV)

University of Arkansas Extension offices in Clark and Hot Spring counties are pitting flies against fire ants in an attempt to mitigate the stinging insect's population in southwest Arkansas.

While experts believe fire ants have existed in Arkansas since the 1950s, the insect is actually native to South America, brought to the United States accidentally on a ship that docked in Mobile, Alabama, in the 1930s.

Although not a native species, the red fire ant has been able to thrive in the southern United States primarily due to its lack of a natural predator.

"Our population densities are five to ten times what South America's are because we don't have any natural predators here," said Amy Simpson, University of Arkansas Extension Clark County.

There is one natural predator of the fire ant - the phorid fly. It's why the fly was introduced to Arkansas's fire ant population roughly a decade ago. Last week, UA Extension offices in Clark and Hot Spring counties began introducing two new species of phorid flies to help wage war against two other types of fire ant at DeGray Lake State Park in Bismarck. They released roughly 700 Pseudacteon obtusus and Pseudacteon cultellatus flies.

The phorid fly acts as a parasite. The female flies attack fire ants and lay their eggs in their thorax - the only way the flies reproduce.

"When it [the egg] goes into the pupa process, it moves into the head capsule and it actually releases an enzyme that dissolves some of the connective tissue which makes the head fall off," said Simpson.

But Simpson said it's not the decapitation of fire ants that's expected to reduce the state's fire ant population, rather it's the fire ants natural fear of the flies that forces them to retreat underground. In turn, the fear of the fly reduces the amount of time fire ants forage for food.

"So they're not bringing as much food back to the colony," said Simpson. "That in turn causes the queen to lay fewer eggs because there's not enough food to support more eggs."

The phorid flies, because they are not native to the U.S., must be cultivated by specially certified entomologists permitted by the federal government. The flies used in Arkansas were grown by the University of Arkansas System Extension Office in Fayetteville. To take care of fire ant colonies in your own yard, UA Extension recommends using fire ant baits that can be purchased at your local hardware or farm supply store.

Although the phorid fly isn't native to Arkansas, Simpson said the flies only target fire ants and don't pose a threat to other naturally occurring insects in the Natural State.

Right now, there are 39 counties in south and central Arkansas that are under red fire ant quarantines. Under the quarantine, certain materials like potted plants, grass sod or baled hay that has come into contact with soil can’t be shipped to non-quarantine areas.

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