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South fights fire ants with pathogen

Fire ant
Fire ant mounds can contain up to 200,000 ants  
June 1, 1998
Web posted at: 7:21 p.m. EDT (2321 GMT)

By Environmental News Network staff

(ENN) -- Fire ants infected with a microorganism from South America were recently released in Hope, Arkansas, and Durant, Oklahoma, to reduce the numbers of the imported ants that now infest 11 states.

The pathogen T. solenopsae infects ant colonies and chronically weakens them. Workers transmit the pathogen to the queen through food exchange. The disease slowly reduces her weight. She lays fewer and fewer eggs, all infected with the pathogen, further weakening the colony.

Known for their burning sting, fire ants are thought to have spread to the United States aboard ships from South America in the early 1930s. The ants now infest an estimated 278 million acres in 11 Southern states and Puerto Rico. They have flourished in the United States because they have no natural enemies there.

Fire ant mounds in open pastures and gardens can contain up to 200,000 ants feeding on the surrounding vegetation. They also are known to attack humans and pets and to invade homes.

Scientists from the U.S. Department of Agriculture's Agricultural Research Service (ARS) are confident that, over time, T. solenopsae can reduce fire ant numbers.

Colony elimination can take from nine to 18 months. However, in lab studies, ARS entomologist David Williams found that after three months, infected colonies were already significantly smaller than healthy colonies.

T. solenopsae, discovered in Brazil in 1973, is the most common pathogen found in fire ants in South America. In 1996, ARS scientists discovered the pathogen in fire ant colonies in Florida, Mississippi and Texas.

The microorganism doesn't harm plants or native ant species. After years of testing, Williams has found T. solenopsae only in red and black imported fire ants. The researchers are now working on mass-producing the pathogen.

Williams and colleagues have already released the microsporidium, along with the Brazilian phorid fly, another natural enemy of the fire ant, at test sites in Florida. The researchers are hoping the pathogen and fly will act as a one-two punch against the fire ants.

Copyright 1998, Environmental News Network, All Rights Reserved

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