Area Wide Suppression of Invasive Fire Ant Solenopsis spp Populations


1USDA/ARS, Center for Medical, Agricultural, and Veterinary Entomology, Fire Ant Unit, 1600 SW 23rd Drive, Gainesville, Florida

32608, USA

2Current address: Entomology and Nematology Department, University of Florida, PO Box 110620, Bldg. 970 Natural Area Drive, Gainesville, FL 32611-0620, USA

ABSTRACT The fire ants Solenopsis invicta Buren and Solenopsis richteri Forel were inadvertently introduced into the USA early in the 1900s and currently inhabit over 150 million hectares in Puerto Rico and twelve southern states from Texas to Virginia. Imported fire ants have also become established in isolated sites in Arizona, California, Maryland, and New Mexico. The large numbers and potent sting of fire ants have resulted in significant medical, agricultural, and environmental impacts. The population densities in the USA are five to ten times higher than in South America, most likely due to their escape from natural enemies. Recently, biological control agents have become available in the USA, e.g. Pseudacteon spp. decapitating fly parasitoids and a microsporidian pathogen Thelohania solenopsae Knell, Allen & Hazard, setting the stage for integrated fire ant management. An area-wide fire ant management project proposal was funded by United States Department of Agriculture-Agricultural Research Services headquarters to demonstrate control of fire ant populations over large areas using commercially available insecticide baits and self-sustaining biological control agents. Untreated, bait control and integrated pest management (IPM) demonstration sites (120 hectares and periphery) were set up in each of five states (Florida, Mississippi, Oklahoma, South Carolina and Texas). The control and IPM sites both had bait (hydramethyl-non and methoprene) applications, but only the IPM site had biological control agents released around the periphery. After 3.5 years, decapitating fly parasites have been established at the demonstration sites. The microsporidian pathogen is established in all sites except Mississippi. Fire ant populations have been reduced by 85-99% in the IPM demonstration sites as compared to untreated areas of the same sites. Environmental assessment has demonstrated that bait toxicants do affect non-target ant species but do not affect the arthropod species richness. Educational outreach activities resulted in informative brochures, the establishment of a programme web site, videos, and general information on fire ants. The research component has responded with additional biological control organisms and better pathogen detection methods.

KEY WORDS fire ants, Solenopsis invicta, Solenopsis richteri, baits, Pseudacteon spp., Thelohania solenopsae, area-wide, integrated pest management

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