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Title: Distribution, abundance and persistence of Orasema spp. (Hym:Eucharitidae) parasitic on fire ants in South America

Author
item VARONE, LAURA - South American Biological Control Lab(SABCL)
item HERATY, JOHN - University Of California
item CALCATERRA, LUIS - South American Biological Control Lab(SABCL)

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2010
Publication Date: 7/16/2010
Citation: Varone, L., Heraty, J.M., Calcaterra, L.A. 2010. Distribution, abundance and persistence of Orasema spp. (Hym:Eucharitidae) parasitic on fire ants in South America. Biological Control.55:72-78

Interpretive Summary: Fire Ants were introduced into the United States and became important economic and urban pests. Since 1970, several surveys have been conducted in South America to find natural enemies. Many organisms were found, and among parasitoids, the wasps from the genus Orasema were studied as candidates for biological control. Surveys along Argentina, Paraguay, Uruguay and Bolivia were conducted to determine the occurrence of the parasitoid attacking fire ant colonies. Once a site with Orasema was found, it was revisited later to assess the persistence of the parasitoid in the field. In total, five different species of Orasema were found in South America and also five fire ant species (Solenopsis) were found parasitized among the surveys. The higher persistence of the parasitoid occurred in rural habitats, in contrast with more anthropic ones, which are likely to interrupt the life cycle of Orasema.

Technical Abstract: Parasitoid wasps of the genus Orasema Cameron have been considered as potential candidates for biological control of imported fire ants in the United States. Surveys were conducted for their occurrence in fire ant colonies across southern South America. In Argentina, 443 ant colonies were excavated at 57 sites and 11 positive sites were revisited to monitor the field persistence. In Paraguay, Bolivia and Uruguay, 288 colonies were examined in the field in 16 sites. Orasema simplex Heraty was the most abundant species, and found in 68% of the total parasitized colonies (n = 72). Orasema xanthopus (Cameron) and Orasema salebrosa Heraty were found at three sites in Argentina. In Bolivia, Orasema pireta Heraty was found at one site and parasitizing an unidentified Solenopsis species. Two new host species for Orasema were discovered, Solenopsis quinquecuspis Forel and Solenopsis macdonaghi Santschi. In addition, Orasema aenea Gahan was found parasitizing fire ants for the first time. The parasitoids persisted at 36.4% of the positive sites, most of them in rural habitats.