Brains are eaten, heads fall off: A new way to kill a pesky pest

If you've got ‘em, you sure don't want 'em. If you don't have 'em, count your blessings, because you're missing a lot of frustration and expense. Unfortunately, given time, you may well have them, too.

Imported fire ants, which came into the United States in 1918 at Mobile, Ala., now infest an estimated 320 million acres in Louisiana, Mississippi, Tennessee, Arkansas, Alabama, California, Florida, Georgia, New Mexico, North Carolina, Oklahoma, South Carolina, Texas, and Puerto Rico, and they continue spreading.

They can be anywhere, as many as 30 million per acre — in pastures, fields, alongside buildings, in hay bales, even inside electrical boxes — and woe betide the person or animal that has the misfortune to stumble into one of the mounds and experience their powerful stings.

The mounds, which can be a foot or more tall, can damage farm equipment and mowers. Billions of dollars are spent yearly to prevent and repair their damage and to cover medical and veterinary costs, according to Robert Vander Meer, who leads the Imported Fire Ant and Household Insects Research Unit at the USDA Agricultural Research Service's Center for Medical, Agricultural, and Veterinary Entomology (CMAVE) at Gainesville, Fla.

Control measures over large areas are often cost-prohibitive and marginally effective. But that may be changing, thanks to efforts by the ARS scientists, who are using phorid flies, tiny insects that attack only fire ants.

According to an article by Sharon Durham in the September issue of the ARS Agricultural Research magazine, there are about 20 phorid species in South America that just love fire ants.

It's a gruesome, horror movie-type scenario: The fly finds a fire ant and lays a single egg inside its body. The immature fly, or maggot, burrows into the ant's head, where it grows without killing its host. Then, just before it reaches maturity, the maggot eats the inside of the fire ant's head, causing it to fall off. The ant's head becomes part of the pupal case from which a little fly emerges to repeat the cycle.

Two phorid species have been established in the United States — a biotype of one attacks the small black and hybrid fire ants now in most of Tennessee and northern Mississippi and Alabama. A second biotype attacks small red fire ants, now established in eight states. An additional decapitating fly is awaiting field release and another is being evaluated in quarantine.

Tiny protozoan parasites that take up residence within the cells of fire ant hosts have potential for controlling the pests. Viral pathogens are also being studied as a possible control by David Oi and Steven Valles in the United States, and Juan Briano in Argentina.

Fire ant biocontrol measures now being employed on more than 100,000 square miles, benefiting more than 20 million people, according to Robert Vander Meer.

“The area-wide fire ant control project is showing the effectiveness of integrated management techniques,” he says, “while improving farm worker safety, reducing mechanical and electrical equipment damage, and lessening pesticide use.”

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