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United States Department of Agriculture

Agricultural Research Service

Title: Introducing Phorid fly parasitoids of red imported fire ant workers from South America to Texas: Outcomes vary by region and by Pseudacteon species released

Authors
item Gilbert, Lawrence - UNIVERSITY OF TEXAS
item Barr, Charles - TEXAS A&M UNIVERS.
item Calixto, Alejandro - TEXAS A&M UNIVERS.
item Cook, Jerry - SAM HOUSTON ST. UNIVERS
item Drees, Bastian - TEXAS A&M UNIVERS
item Lebrun, Edward - UNIVERSITY OF TEXAS
item Patrock, Richard - UNIVERSITY OF TEXAS
item Plowes, Robert - UNIVERSITY OF TEXAS
item Porter, Sanford
item Puckett, Robert - TEXAS A&M UNIVERS.

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 14, 2007
Publication Date: March 1, 2008
Citation: Gilbert, L.E., Barr, C.L., Calixto, A.A., Cook, J.L., Drees, B.M., Lebrun, E.G., Patrock, R.J., Plowes, R.M., Porter, S.D., Puckett, R.T. 2008. Introducing Phorid fly parasitoids of red imported fire ant workers from South America to Texas: Outcomes vary by region and by Pseudacteon species released. Southwestern Entomologist.33(1):15-29.

Interpretive Summary: Since the first status report on Pseudacteon decapitating fly introductions to Texas, there have been significant developments in release activities across a range of release sites by a variety of participants in Texas and the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL. Systematic and widespread monitoring of population expansion of Pseudacteon flies has been ongoing. Prior to 2002, establishment success by the widely released initial species, P. tricuspis, was poor. Severe drought (1996-2001) and the small size of workers in colonies with multiple queens are likely reasons for the poor success. In recent years, favorable weather, irrigation of release sites, and the use of a smaller Pseudacteon species (P. curvatus) have improved the success of field releases. Beginning in 2002, the USDA-APHIS collaboration with USDA-ARS, and Texas Cooperative Extension programs, began to supplement release sites in Texas beyond those initiated by the UT Austin phorid fly project. In 2005, private citizens began to participate in the spread of Pseudacteon to new sites. As of fall 2006, P. tricuspis, expanding from releases conducted between 1999 and 2001, can be found in over more than 7 million acres of Central and Coastal Texas, while P. curvatus, with its later start, is only now beginning an expansion phase in some sites. South Texas continues to present problems for Pseudacteon populations that have established more easily in mesic and moderate climates. However, recently two prior “failed” sites were revealed to be false negatives after the record rains of summer 2007. Starting in late 2006, the first releases of P. obtusus in North America have resulted in establishment, and releases of 3-5 additional species are underway. Results of this paper are important because they document successful field releases of fire ant decapitating flies in Texas, thus allowing cooperating scientists to determine where additional releases are needed, which species are successful where, and what release techniques are most effective.

Technical Abstract: Since the first status report on Pseudacteon decapitating fly introductions to Texas there have been significant developments in release activities across a range of release sites by a variety of participants. Systematic and widespread monitoring of population expansion by established Pseudacteon populations has been ongoing. Prior to 2002, establishment success by the widely released initial species, P. tricuspis, was poor. Two factors, severe drought in 1996-2001, and host-size dependent sex ratio were proposed constraints on establishing this species. In recent years however, these limitations have been lifted in some areas by periods of favorable weather, irrigation of release sites, and/or by use of a smaller Pseudacteon species, P. curvatus, not reliant on larger fire ant workers to produce females. Beginning in 2002, the USDA-APHIS collaboration with USDA-ARS and Texas Cooperative Extension programs, began to supplement release sites in Texas beyond those initiated by the UT Austin phorid fly project. In 2005, private citizens began to participate in the spread of Pseudacteon to new sites. As of fall 2006, P. tricuspis, expanding from releases conducted between 1999 and 2001, can be found in over more than 7 million acres of Central and Coastal Texas, while P. curvatus, with its later start, is only now beginning an expansion phase in some sites. South Texas continues to present problems for Pseudacteon populations that have established more easily in mesic and moderate climates. However, recently two prior “failed” sites were revealed to be false negatives after the record rains of summer 2007. Starting in late 2006, the first releases of P. obtusus in North America have resulted in establishment, and releases of 3-5 additional species are underway.

Last Modified: 10/1/2014
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