Introduction of fire ant biological control agents into the Coachella Valley of California

Authors: Oi, David; Valles, Steven; Porter, Sanford; CAVANAUGH, CHRISTOPHER - Coachella Valley Mosquito And Vector Control District; WHITE, GREGORY - Salt Lake City Mosquito Abatement District; HENKE, JENNIFER - Coachella Valley Mosquito And Vector Control District

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2018
Publication Date: 3/20/2019
Citation: Oi, D.H., Valles, S.M., Porter, S.D., Cavanaugh, C., White, G., Henke, J. 2019. Introduction of fire ant biological control agents into the Coachella Valley of California. Florida Entomologist. 100(1):284-286. https://doi.org/10.1653/024.102.0156.
DOI: https://doi.org/10.1653/024.102.0156

Interpretive Summary: The red imported fire ant is a stinging, invasive ant from South America that has plagued the southern U.S. since the 1930s. It is now established in parts of California, including the Coachella Valley, which has a hot, dry, desert climate. Under these conditions, fire ants generally inhabit the irrigated, urban landscapes. In an effort to help suppress fire ant populations, we successfully introduced natural enemies of the fire ant into the Valley. These enemies consisted of two tiny flies that are fire ant parasites, a virus, and a microsporidian pathogen. These biological control agents, originally from South America, but are now established in the southern U.S., were transported from Florida and released into fire ant colonies in the vicinity of Palm Desert, California. This is the first establishment of fire ant parasitic flies, which decapitate fire ants, in California. In addition, we demonstrated successful inoculations of the pathogens into fire ants in a desert climate. While we discovered the pathogens were naturally present in the Valley, both pathogens have increased in prevalence and spread at the inoculation sites. It is still too early to determine the impact of the biological control agents on the fire ant populations this unique urban desert habitat.

Technical Abstract: The red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), is a stinging, invasive ant from South America that has plagued the southern USA since the 1930s. It is currently established in parts of California, including the Coachella Valley. We introduced and established the fire ant decapitating phorid flies, Pseudacteon curvatus Borgmeier and Pseudacteon obtusus Borgmeier (Diptera: Phoridae); Solenopsis invicta virus 3 (Picornavirales: Solinviviridae) (SINV-3); and the microsporidian fire ant pathogen Kneallhazia solenopsae Knell, Allan, & Hazard (Microsporida: Thelohaniidae) for the biological control of fire ants in California. All of the introduced biocontrol agents were collected for 2–3 years after their release. This is the first establishment of fire ant decapitating phorid flies in California. In addition, we demonstrated human mediated establishment of SINV-3 and K. solenopsae in hot, dry, but irrigated, urban desert habitat.