Parasitoids and pathogens used against imported fire ants in the southern United States

Authors: Oi, David; PORTER, SANFORD - Retired ARS Employee

Submitted to: Contributions of Classical Biocontrol to the U.S. Food Security, Forestry, and Biodiversity, 1985-2022
Publication Type: Book / Chapter
Publication Acceptance Date: 5/12/2022
Publication Date: 6/1/2022
Citation: Oi, D.H., Porter, S.D. 2022. Parasitoids and pathogens used against imported fire ants in the southern United States. In: Van Driesche, R.G., Winston, R.L., Perring, T.M., and Lopez, V.M. (eds.) Contributions of Classical Biocontrol to the U.S. Food Security, Forestry, and Biodiversity. Morgantown, WV:USDA-Forest Service. p. 252-265.

Interpretive Summary:

Technical Abstract: The red imported fire ant (Solenopsis invicta), black imported fire ant (Solenopsis richteri), and their hybrid, collectively called imported fire ants, or fire ants, are invasive ants that have become ubiquitous throughout the southern United States. They are aggressive ants that inflict painful stings, which in some cases, cause anaphylaxis. Their large, dominant populations can result in damage to crops, livestock, wildlife, and infrastructure (e.g., electrical equipment) with total estimated costs of over $8 billion annually for damage and control. Both the red and black species were well established and spreading in the United States by the late 1930s. An imported fire ant quarantine (>365 million acres) is established in the US to slow transport of materials with fire ants into uninfested areas. Fire ant stings are a major problem for people, livestock, and pets with control measures often requiring recurring insecticide treatments. Fire ants can thrive in a wide array of habitats, including unmanaged and/or inaccessible landscapes which serve as reservoirs for infestation of inhabited areas. Biological control is arguably the only viable regional strategy to suppress established populations of invasive ants. Six species of parasitoid flies and two pathogens (a microsporidium and a virus) have been released (1997 – 2014) and established for the biological control of fire ants in the USA. The flies attack worker ants and inhibit their foraging, while the pathogens cause the debilitation of queens and workers. Dramatic declines in fire ant populations have not occurred, but there is evidence for gradual long-term declines. Also, biocontrol agents appear to slow the reinfestation of areas temporarily cleared of fire ants via insecticide treatments. These agents represent the first concerted efforts to utilize classical and augmentative biological control for the long-term suppression of invasive fire ants. Knowledge gained from these efforts will facilitate projects to improve the biological control of fire ants and other invasive ants.