Areawide Suppression of Fire Ant Populations in Pastures: Project Update 1,2

The red imported fire ant, Solenopsis invicta (Hymenoptera: Formicidae), is an invasive species that creates serious medical and agricul- tural problems, damaging many crops and cattle production. Its annual eco- nomic impact to the US economy is approximately $6 billion. The integration of chemical bait insecticides and biological control agents is used in an area- wide management program for fire ants coordinated by USDA-ARS Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, Florida. Control sites, where no biological control agents were released, and biocontrol treatment sites, where both decapitating flies and the microsporidium Thelo- hania solenopsae were released, have been established in five states (Florida, Texas, Mississippi, Oklahoma, and South Carolina). All sites received chemi- cal bait applications of a 1:1 mixture of hydramethylnon and methoprene baits applied at a rate of 1.7 kg per ha. To evaluate the effect of the treatments on the arthropod biodiversity, pitfall traps were used twice a year. Decreases in fire ant populations have been observed at the different demonstration sites. The decapitating fly Pseudacteon tricuspis (Diptera: Phoridae) has been estab- lished at demonstration sites in three states (Florida, Texas, and South Caro- lina); P. curvatus was established in Mississippi, Florida, and South Carolina. The disease T. solenopsae has been established in four states (Florida, South Carolina, Texas, and Oklahoma), and continues to spread. This new approach to fire ant control may have a significant impact on the future management of fire ant populations.