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Entomologist Jian Chen checks the repellency of specific compounds using a new bioassay he developed based on digging behavior of fire ants. Click the image for more information about it.

Ganging up to Stop Fire Ants

By Alfredo Flores
December 10, 2004

Fire ants and the U.S. South have been synonymous since the ants' arrival in Alabama in 1918 aboard merchant ships from South America. The pests found their way onto land and have been multiplying and migrating ever since.

Researchers at the Agricultural Research Service, the chief scientific research agency of the U.S. Department of Agriculture, are working diligently to curb the spread of these troublesome pests, which have stung countless humans and damaged electrical and farm equipment. They even attack and kill young cattle and other livestock, as well as vulnerable wildlife.

To combat this ongoing problem, scientists in the ARS Biological Control of Pests Research Unit at Stoneville, Miss., and the Biological Control and Mass Rearing Research Unit at Starkville, Miss., are conducting regional integrated management programs in Mississippi, Alabama and Tennessee. The programs are designed to implement and test biological control agents against red and black imported fire ants (Solenopsis invicta and S. richteri, respectively) and their hybrid. Two specific areas are the focus of the programs: the Natchez Trace Parkway, maintained by the National Park Service, and south-central Tennessee's nursery crops production region.

Establishment of biological control agents in central Tennessee may slow the spread of the ants into nursery areas. Currently, a pathogen and several species of parasitoid flies--including the decapitating phorid fly from the genus Pseudacteon--are the most effective known biological control agents.

The Stoneville unit has reared thousands of phorid flies for research and field releases. One tiny species, P. curvatus, has been successfully established on black and hybrid fire ants in a multistate release program that began in 2002. Flies released in two pastures in Clay County, Miss., now occupy approximately 560,000 acres up to a distance of more than 28 miles from the release sites.

Also being implemented is an Integrated Pest Management approach that combines tactics such as distribution of insecticidal baits with natural organisms. Chemical bait treatments alone are not sustainable, because fire ants will reinfest previously treated areas. However, baits can be very effective, consistently killing more than 90 percent of colonies in an area when applied correctly.

Read more about this multifaceted fire ant research in the December issue of ARS' Agricultural Research magazine.