Importation biological control of invasive fire ants with parasitoid phorid flies—progress and prospects

Abstract

Twenty-two known species of Pseudacteon flies (Diptera: Phoridae) are parasitoids of South American fire ants in the Solenopsis saevissima (Smith) complex. Phorid flies of different sizes and with differing activity patterns have been released in the United States to control two imported fire ant species—Solenopsis richteri and Solenopsis invicta—and their hybrid. Six highly host-specific Pseudacteon species have been successfully established at dozens of release sites and most are now widely distributed across areas infested by imported fire ants. This complex of released fly species is expected to weaken the competitive vigor of fire ant colonies through both direct and indirect effects, and eventually reduce the abundance of imported fire ants. To date, however, few studies have attempted to document the effect of these parasitoids on host ants in the field, and future research should focus on the overall magnitude of reduction in host ant populations. Knowledge gained from the successful importation and establishment of South American phorid flies in the US can provide guidance for utilization of these parasitoid flies for biological control of S. invicta in other introduced ranges, and aid the search for additional importation biological control agents of pest ants in general.