Host Specificity of the Microsporidian Pathogen Vairimorpha invictae at Five Field Sites with Infected Solenopsis invicta Fire Ant Colonies in Northern Argentina

Sanford D. Porter, Steven M. Valles, Timonthy S. Davis, Juan A Briano, Luis A. Calcaterra, David H. Oi, R. Austin Jenkins


The microsporidian pathogen Vairimorpha invictae is being evaluated for release in the United States as a potential self-sustaining biological control agent for imported fire ants. We examined the host range of this pathogen at 5 sites in northern Argentina where Solenopsis invicta Buren fire ant colonies had high levels of infection (28-83%). At 3 sites near the city of Corrientes, we examined 509 non-Solenopsis ants from 61 collections, 12 genera, and 19 species with a polymerase chain reaction-based screening procedure. No V. invictae infections were detected in any of the samples. At 2 sites near San Javier in Santa Fe Province, 350 km to the south, we screened another 438 non-Solenopsis ants from 44 baits, 4 genera, and 4 species, again with no infections. At the Corrientes sites, we also examined 235 non-ant arthropods from 10 orders, 43 families, and more than 80 species. None were infected with V. invictae. The results of this study indicate that, in its native South American range, V. invictae is specific to Solenopsis fire ants.

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