Parasites successfully infect, destroy fire ant mounds

Two protozoan parasites are showing promise in the fight against imported fire ants.

On the heels of the successful release of phorid flies to control fire ants, USDA’s Agricultural Research Service is testing Thelohania solenopsae and Vairimorpha invictae. The parasites live in their host’s cells and infect the mound.

Worker ants transfer T. solenopsae spores to the queen, possibly through food. Infection reduces the queen’s egg laying, so colonies die out.

“Though we found that natural field infections of T. solenopsae were more prevalent in fire ant colonies with several queens, we also confirmed that single-queen colonies were susceptible to infection,” said ARS entomologist David Oi.

V. invictae successfully destroyed fire ant mounds, and researchers proved the parasite doesn’t infect non-fire ants or other arthropods.

“This is important because it shows that this pathogen may also be suitable for release in the United States with little or no risk,” Oi said.

ARS researchers also discovered the first virus known to infect red imported fire ants -- Solenopsis invicta virus-1. It’s been associated with the deaths of immature ants. Infected ants don’t usually show symptoms unless they encounter certain stressors. Then, viral replication increases within them, and their brood later dies.

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For more: David Oi, ARS, (352) 374-5987; david.oi@ars.usda.gov.