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United States Department of Agriculture

Agricultural Research Service

Title: Impact of Microsporidian Pathogen, Thelohania Solenopsae, on Red Imported Fire Ants

Authors
item Williams, David
item Oi, David

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: April 6, 1998
Publication Date: N/A

Interpretive Summary: Imported fire ants are a significant pest of the southern United States, where its ability to sting, damage crops, and reduce biodiversity make it a concern in urban, agricultural, and wildlife areas. Thelohania solenopsae is a pathogen of imported fire ants that can infect the ovaries of fire ant queens. This pathogen slowly debilitates a queen so that her reproductive capacity diminishes and she eventually dies. Previously, this pathogen wa known only from South America. In 1996, T. solenopsae was discovered in several locations in Florida, and limited surveys throughout the southern U.S. revealed that infections were present in Texas and Mississippi. In this study we provide the first documentation of artificially initiated transmission of T. solenopsae among fire ant colonies by providing colonies with infected immature ants. The laboratory inoculations resulted in significant reductions in immature ants and adults. Lower egg laying rates, queen weights, and queen survivorship was also documented from infected colonies. Artificial inoculations resulting in infections of red imported fire ant colonies under field conditions was also demonstrated for the first time. The ability to artificially infect S. invicta colonies with T. solenopsae should facilitate the assessment and development of this pathogen as a biological control agent of imported fire ants.

Technical Abstract: Thelohania solenopsae, an entomopathogenic microsporidium from South America, was discovered in the United States by Williams et al. (1998) in red imported fire ants, Solenopsis invicta, collected in several locations in Florida. Limited surveys throughout the southern U.S. revealed that infections also were present in Texas and Mississippi. Studies conducted on the impact of this pathogen on laboratory colonies of red imported fire ants indicated that inoculated colonies had significantly lower brood volume, worker populations, and queen weights than control colonies. Reductions in brood and workers were evident at 10 and 12 weeks after inoculation, respectively. At the end of the study (week 23), there was an average of 6 ml brood per colony from inoculated colonies in contrast with 50 ml in the controls. In field studies, T. solenopsae infections were detected in four of the five inoculated colonies 18 weeks after infected brood was introduced. After 11 months, there was a 30% reduction in the average population index for the inoculated colonies in contrast to a 4% increase in the controls. This is the first documentation of artificially initiated horizontal transmission of T. solenopsae infections among fire ant colonies.

Last Modified: 10/21/2014
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