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LIVINGSTON, Texas — The U.S. Department of Agriculture's Animal and Plant Health Inspection Service, in conjunction with Texas Cooperative Extension, released phorid flies in Polk County in late October to combat the red imported fire ant. Extension Agricultural Agent Mark Currie selected the release site on the property of Marty Lowe. Currie, with the help of Master Gardener volunteers Maurice and Nancy Petersen of Livingston, released the flies. Training and supervision for this effort were provided by Dr. Bastiaan M. Drees, professor and Extension entomologist, and Alexandro Calixto, Extension assistant. The phorid flies were screened for host-specificity to the red imported fire ant and mass-reared, Drees said. The red imported fire ant, accidentally introduced into the southern United States, spread into East Texas starting in the 1950s. Because its enemies were not imported from South America at the time, the ant has had the advantage over native ant species of having few predators, parasites or diseases that help keep the population in check in its native habitats. Since 1997, researchers with the USDA, University of Texas, in cooperation with the Texas Imported Fire Ant Research and Management Project lead by the Texas Agricultural Experiment Station at Texas A&M University, have been studying several groups of organisms that show promise for spreading naturally and sustaining themselves in the environment, Drees said. "If successful, these efforts could lead to sustained suppression of imported fire ant populations through classical biological control," he said. The parasites released are from a group of flies called Phoridae. The phorid fly species being released, Pseudacteon tricuspis, was imported from South America and mass-produced by the Florida Department of Food and Agriculture with funding from the USDA. "These very tiny flies bombard worker fire ants and inject eggs in the thorax of the ants," he said. When successful, eggs hatch into larvae that migrate into the ant's head capsule to complete development over a month or two. When the flies emerge, they seek new host ants. They are host-specific and do not affect any other ants or animals, he said. However, when the ants detect the presence of the flies, they stop foraging and hide. This behavioral shift is believed to help native ant species, enabling them to find food, build nests and better compete with the exotic imported fire ants. This species of phorid fly has been released at more than 20 locations in Texas, Drees said. At about six of those locations, the flies have survived and have begun to spread. In Florida, an early release has spread to more than 500 square miles, he said. "Several years may be required for the fly populations to build up enough to have a suppressive effect on the fire ant," he noted. Several other organisms, including a disease of fire ants called Thelohania, and several other species of phorid flies are currently being investigated. A number of organisms will need to be released and established to duplicate the situation in South America, where the fire ant is not considered to be a major pest, Drees said. |
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