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Title: New survey for the fire ant microsporidia Vairimorpha invictae and Thelohania solenopsae in southern South America, with observations on their field persistence and prevalence of dual infections.

Author
item BRIANO, JUAN
item CALCATERRA, LUIS
item Valles, Steven
item LIVORE, JUAN

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2006
Publication Date: 10/20/2006
Citation: Environmental Entomology, Vol. 35, No. 5, October 2006 pp.1358-1365

Interpretive Summary: The classical biological control approach of the red and black imported fire ants with diseases has been considered since the 1970´s. Two infections mentioned in this work are intracellular microorganisms specific to fire ants that were originally discovered infecting the red imported fire ant in Mato Grosso, Brazil, and later found in other species of South American fire ants. Since 1988, surveys for these two pathogens have been conducted intensively in Argentina because there is a continued need to expand explorations to find high prevalence of infections. A new exploration was conducted in Argentina, Paraguay, Chile, Bolivia, and Brazil and three sites with high prevalence of pathogens were monitored periodically for the persistence of the infections. Information reported in this manuscript confirms that these diseases are promising classical biological control agents of the imported fire ants in the United States.

Technical Abstract: The exploration for the fire ant diseases Vairimorpha invictae Jouvenaz and Ellis (Microsporidia: Burenellidae) and Thelohania solenopsae Knell, Allen, and Hazard (Microsporidia: Thelohaniidae) was conducted from 2001 to 2005 in Argentina, Paraguay, Chile, Bolivia, and Brazil. A total of 2,064 colonies were sampled from 262 sites. Three sites with high prevalence of pathogens were monitored periodically for the persistence of the infections. Vairimorpha invictae occurred at 12% of the sites and in 10% of the colonies. Except for one infected colony in Bolivia, its distribution was restricted to the eastern part of the region surveyed. The highest occurrence was in Santa Fe Province. Thelohania solenopsae presented a much wider distribution. It occurred at 25% of the sites and in 13% of the colonies. The highest occurrence was in Buenos Aires Province. This is the first report of T. solenopsae in the northwest, in the west, in central Argentina, and in Bolivia, and infecting S. interrupta (Santschi). Simultaneous infections were found at 4% of the sites and in 2.2% of the colonies. The periodical examination revealed high infection levels in most occasions. The prevalence of T. solenopsae ranged from 10 to 90% of the colonies, V. invictae from 0 to 60%, and dual infections from 0 to 50%. Each microsporidium exhibited a characteristic enzootic/epizootic wave. Successive epizootic levels observed in both infections provide a more constant pressure against fire ant populations. These diseases are promising classical biological control agents of the imported fire ants in the United States.