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United States Department of Agriculture

Agricultural Research Service

ARS Releases New Artillery in the Fight Against Fire Ants

By Tara Weaver
May 29, 1998

A microorganism from South America is the latest biological weapon against the red imported fire ant. ARS researchers and state cooperators released fire ants infected with T. solenopsae this week at sites in Hope, Ark., and Durant, Okla.

The scientists are confident that, over time, this promising biocontrol agent can reduce fire ant numbers. The ants now infest millions of acres across 11 southern states.

The pathogen, technically a microsporidium, 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.

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

Other states slated for possible limited releases of T. solenopsae include Alabama, Tennessee, South Carolina, Georgia, North Carolina, Virginia and Louisiana.

Scientific contact: David F. Williams, Imported Fire Ant and Household Insects Research Unit, Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Fla., (352) 374-5982, fax 374-5984,

Last Modified: 5/15/2017
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