Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/1998
Publication Date: N/A
Citation: Interpretive Summary: Researchers at the Center for Medical, Agricultural and Veterinary Entomology of the USDA's Agricultural Research Service have been studying phorid flies in the genus Pseudacteon as possible classical biological control agents for imported fire ants. In order to evaluate their safety for field release in the United States, they tested the host specificities of three species of these flies in quarantine facilities in Gainesville, Florida. Female flies from Brazil were placed into test trays containing either red imported fire ants, tropical fire ants, or native ants from six other genera. The three species of flies tested were all at least 15 times more likely to attack imported fire ants than they were to attack native fire ants. More than 200 larvae resulted from numerous attacks on imported fire ants, but none from the few possible attacks on native fire ants or the other species of ants tested. These results indicate that release of these flies in the United States poses little or no threat to native ants.
Technical Abstract: Host specificities of three species of Pseudacteon decapitating flies (P. litoralis Borgmeier, P. tricuspis Borgmeier, P. wasmanni Schmitz) were tested in quarantine facilities in Gainesville, Florida, USA. Female flies from Brazil were placed into test trays containing either red imported fire ants (Solenopsis invicta Buren), tropical fire ants (Solenopsis geminata Forel), or native ants from six other genera (Crematogaster, Pheidole, Aphaenogaster, Neivamyrmex, Forelius, Camponotus). Tests lasted 60-90 min. The three species of flies tested were all at least 15 times more likely to attack their natural host, S. invicta, than they were to attack the native fire ant, S. geminata. More than 200 larvae resulted from numerous attacks on S. invicta workers. No larvae resulted from the few possible attacks on S. geminata or the other species of ants that were tested. We induced several P. tricuspis to attack a few S. geminata workers by mixing these workers in with freeze-killed S. invicta workers. One adult fly emerged from these attacks, demonstrating that P. tricuspis can develop in S. geminata workers. This indicates that field release of P. tricuspis poses some risk to native fire ants; however, the extremely low rates of attack on S. geminata in the lab and in the field indicate that this risk would be minimal. The argument is made that this small risk is acceptable because, among other things, native fire ants are under much more risk from expanding populations of imported fire ants than they would be from imported Pseudacteon flies.