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Researchers test biological weapon in war against fire ants

Web posted June 3, 1998

Associated Press

DURANT, Okla. -- The fire ants in a pasture near Durant may find themselves on sudden diets if a microorganism released by scientists works as expected.

U.S. Agriculture Department researchers unleashed the pathogen, T. solenopsae, last week near Durant and Hope, Ark., to test what they believe is a natural new weapon for controlling the invasive insect.

``What happens has been on the queen herself. It's like she's on a crash diet that starts impacting her ability to lay eggs,'' said David Williams, an entomologist with the Agricultural Research Service in Gainesville, Fla. ``Instead of laying 900 eggs a day, pretty soon she's only laying 30 eggs.''

The red imported fire ant infests millions of acres in 11 southern states. It has been spreading since its arrival from South America in the 1930s.

The ants can attack and sting repeatedly, sometimes resulting in death for people with allergies. Their big lumpy hills can wreck lawns and damage farm equipment.

In laboratory studies, Williams found that the populations of fire ant colonies infected with T. solenopsae were significantly reduced after three months.

Scientists first found the pathogen occurring naturally in Brazil fire ant colonies in 1973. Two years ago they discovered it in colonies in Mississippi, Florida and Texas.

The microorganism appears to be specific to fire ants and does not harm plants or native ant species, Williams said.

``We see that this pathogen really works,'' he said.

A sure sign of the disease is when the queen begins to lose weight. She grows weak and lays fewer and fewer eggs, all of which are infected with the pathogen and further weaken the colony.

``The beauty of this thing we have is once you inoculate five or 10 colonies, the disease spreads on its own,'' Williams said.

The disease works slowly with colony elimination taking nine to 18 months.

In the field tests, scientists are trying to infect the colonies by releasing infected immature ants. Williams said it will be eight to 10 weeks before they know if they were successful.

Researchers believe the microorganism will prove much more cost effective than current eradication methods that also can harm native ants. They are working on mass producing the pathogen.

``There are many large areas where baits are too expensive,'' Williams said. ``They also have an environmental impact.''

Scientists also plan to test the pathogen in Alabama, Tennessee, South Carolina, Georgia, North Carolina, Virginia, Mississippi and Louisiana. The study is expected to take one to two years.