The red imported fire ant (Solenopsis invicta) in the West Indies: distribution of natural enemies and a possible test bed for release of self-sustaining biocontrol agents

Authors: Valles, Steven; WETTERER, JAMES - Florida Atlantic University; Porter, Sanford

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/17/2015
Publication Date: 12/1/2015
Citation: Valles, S.M., Wetterer, J.K., Porter, S.D. 2015. The red imported fire ant (Solenopsis invicta) in the West Indies: distribution of natural enemies and a possible test bed for release of self-sustaining biocontrol agents. Florida Entomologist. 98(4):1101-1105.

Interpretive Summary: The red imported fire ant was introduced into the United States in the 1930s and currently infests about 300 million acres. It causes approximately $6 billion in damage annually and can pose a serious threat to human health from allergic reactions. Biological control agents are thought to provide the most sustainable, cost-effective and wide-reaching control of this ant in the USA. Indeed, the major biological control agents against the fire ant in the USA currently were discovered and/or released by scientists in ARS. Studies were conducted by scientists in the Imported Fire Ant and Household Insects Research Unit (ARS), Gainesville, Florida, and Florida Atlantic University to test their hypothesis that biological control agents were largely absent on these islands. Indeed, the fire ant populations on these islands appear to be largely devoid of natural enemies. The isolated habitat offers the ability to quantify the impact of intentionally released natural enemies alone, or in combination, on S. invicta populations in a relatively short time frame.

Technical Abstract: Sample collections of Solenopsis invicta (Hymenoptera: Formicidae) were taken from 20 islands of the West Indies and evaluated for the presence of key pathogens and parasites of this invasive pest ant. We hypothesized that bottleneck events during the introduction of this ant species in the West Indies would have resulted in populations devoid, or nearly so, of natural enemies. Monogyne and polygyne social forms were found throughout the islands examined with monogyny being more prevalent (65%) compared with polygyny (35%). Among 254 samples, only 25 (~ 10%) tested positive for the presence of pathogens or parasites. The microsporidian Kneallhazia solenopsae was the most prevalent pathogen detected; it was found in 20 colonies. A second microsporidian species, Vairimorpha invictae, was shown to be present in a polygyne sample collected from St. Croix—the first detection of this pathogen outside South America. Similarly, Solenopsis invicta densovirus (SiDNV) was detected in one polygyne sample from Anguilla. SiDNV is not found in S. invicta US populations so this detection also represents the first geographic discovery outside of South America. Two species of Pseudacteon decapitating flies were found to have dispersed into the Bahamas. Utilization of the islands of the West Indies for release, establishment, and impact assessment of S. invicta natural enemies is discussed.