86(3)September 2003FIELD RELEASES OF THE DECAPITATING FLY PSEUDACTEON - PDF document

86(3)September 2003FIELD RELEASES OF THE DECAPITATING FLY PSEUDACTEON CURVATUS(DIPTERA: PHORIDAE) FOR CONTROL OF IMPORTED FIRE ANTS (HYMENOPTERA: FORMICIDAE) IN ALABAMA, FLORIDA, AND TENNESSEEThe little decapitating ßy, Borgmeier, was released at 11 sites in Ala-bama, Florida, and Tennessee as a potential self-sustaining biocontrol agent of imported Þreants. We used a biotype from Buenos Aires Province, Argentina that parasitizes black ÞreSolenopsis richteri Forel). Generally, several thousand ßies were released as larvae inparasitized ant workers over a 1-2 week period. Solenopsis richteri) at a site near Tal-ladega, Alabama where they have persisted more than two years and expanded out 5-20 kmfrom the original release site. Flies failed to establish in Florida and Tennessee although afew 1st-generation Þeld-reared ßies were recovered at four sites in Florida. This ßy is onlyother pest ant species. Possible reasons for failures at the other sites include insufÞcient veg-etation cover, competition with another species in Florida, severe winter kill ofants at a site in Tennessee, and the possibility that the biotype of released wasnot a viable parasitoid of red imported Þre ants.ey Words: Solenopsis richterihybrid Þre ants, classical biocontrol, par-asitoid, southeastern United Statesen Alabama, Florida y Tennessee como un agente auto-sostenible de control biol—gico de lahormigas de fuego importadas. Usamos un biotipo de la Provincia de Buenos Aires, Argen-Solenopsis richteriorel). Generalmente,un periodo de 1-2 semanas. Las moscas Solenopsis richterisitio cerca de Talladega, Alabama en donde persistieron por m‡s de dos a–os y se expandie-r—n 12 km del sitio original donde fueron liberadas. Aunque hormigas de la primera genera-ci—n criadas en el campo fueron colectadas en cuatro sitios en Florida, las moscas nopudieron establecerse en Florida y Tennessee. Esta mosca es solamente el segundo parasi-toide de uso en control biol—gico que h‡ sido exitosamente liberado para el control de las hor-migas importadas de fuego o cualquier otra especie de hormiga. Posibles razones por el falloen otros sitios incluye insuÞciente cubrimiento de vegetaci—n, competici—n con otras especiesen Florida, una muerte severa invernal de las hormigas en un sitio en Ten-nessee, y la posibilidad de que el biotipo de viable de las hormigas rojas de fuego importadas. Translation provided by Demian Kondo.When the black imported Þre ant, richteriorel, and the red imported Þre ant, Buren, were accidentally intro-years ago, almost all of their natural enemieswere left behind in South America (Jouvenaz1990). The absence of natural enemies is a likelySouth America (Porter et al. 1992; Porter et al.1997). Importation of some of the natural enemiesleft behind in South America (Williams et al. Graham et al.: Fire Ant Decapitating Fly335favor of our native ants (Porter 1998b). If thathappens, imported Þre ant populations in theUnited States may decrease to levels similar tothose in South America where Þre ants are notgroup of natural enemies that have shown somepromise in the battle against Þre ants (Porter1998b; Folgarait & Gilbert 1999). One species,Borgmeier, is already per-around Gainesville, FL (Porter et al. 2003), Þvesites in Alabama (Graham et al. 2001), plus addi-tional sites in at least six other states. lar interest. It has been reared in large enoughnumbers for inoculative releases (Vogt et al. 2003)and it attacks only small Þre ants (Morrison et al.1997). Consequently, it has the potential of greatlywhichonly attacks medium and medium-large Þre ants(Morrison et al. 1999).richteriThe objective of this study was to determine ifin the United States. We were particularly inter-ested in determining whether this ßy could be es-tablished on populations of red imported Þre ants,black imported Þre ants and/or their hybrid. Thisinformation was especially important for Ala-bama and Tennessee. About half of Alabama isoccupied by black and hybrid Þre ants and Ten-hybrid or black imported Þre ants.ville, FL on red imported Þre ants. They were col-lected from El Toro Ranch east of Las Flores,Buenos Aires Province, Argentina in March of1997 (Porter 2000). Approximately 1000 parasit-Solenopsis richteriported into the Center for Medical, Agriculturaland Veterinary Entomology (CMAVE) quarantinefacilities in Gainesville, FL.all of 1999 after S.D. Porter obtained permissionfrom the State of Florida and a Finding Of No Sig-niÞcant Impact (FONSI) was issued by the USDA-environment. The FONSI was issued after a selectrelease. Subsequently, the USF&WS, Region 4as consulted about the release. State permitswere also obtained for Þeld releases in Alabama(K. Flanders) and Tennessee (R. M. Pereira).The release site in Alabama was between At-lanta, GA and Birmingham, AL, approximately 3km east of Talladega, AL (Table 1). Ants at thisrichteridrocarbon pattern (Vander Meer et al. 1985). Therelease site was a 3.6 ha triangular cattle pasturepine forest, a county road, and a small stream.drained corner to swampy area near the stream.marked with numbered ßags. Because cattle tendto pull up ßags, a circle was painted on the groundsurrounding the mound and a number waspainted near the mound. Approximately Þvegrams of workers were collected from each moundand placed into tightly sealed, vented, plastic con-numbers. The containers with workers insidewere placed into cloth containment bags inside astyrofoam cooler with an ice pack and shippedovernight to the ARS lab in Gainesville, FL on thesame day that the ants were collected. Workerswere collected from 13 mounds on 8 May 2000, 6mounds on 10 May, 6 mounds on 17 May, and 13mounds on 23 May, for a total of 38 mounds overa 15-day period.Upon receipt in Gainesville, the workers wereremoved from the containers and allowed to crawllarge to be parasitized. One or more groups of 1.0g of workers were weighed from each colony andeach was added to about 1.0 g of brood. Brood was 86(3)September 2003earlier just south of Chattanooga TN. The pres-ence of sufÞcient brood is critical, because with-out it, the workers ÔfreezeÕ during ßy attacks,numbers of workers.into large automatic attack boxes similar to theimproved version described by Vogt et al. (2003)where they were exposed to attacks by ßies for 2-3 days. The newly parasitized workerswere collected and most of the brood was removedwith sorting sheets (Banks et al. 1981) before theworkers were repackaged and shipped overnightto Talladega County, AL for release. Within 24hours of receipt, these workers were released intothe same mound from which they were originallyremoved. This was done by placing the openedcause workers to emerge. Generally, the parasit-ized workers were recruited back into the moundin 10-20 min. When conditions were hot andsunny, ants were shaded until the ants rejoinedtheir nestmates inside the mound. On one occa-sion, we were unable to locate a nest for release ofthe parasitized workers. Release was attemptedmound had relocated, but the workers were ob-served to Þght, indicating that it was not the orig-inal colony. Most of the workers released into thismound were assumed to have perished.throughout the summer were hot and dry. Thesummer of 2000 was the second summer of a two-year drought in the area. From May until August,mean daily maximum air temperatures averagedperatures averaged 26.7¡C. Total rainfall duringthese months was only 153 mm compared to 436mm under normal weather conditions.turbing 5-8 mounds in the release area. Severalcrushed in the disturbed area of the mound in or-der to attract the ßies more quickly. Mounds werephorid ßies.200038 HIFA (mono)Pasture with tall grass, well drained to wetCMAVE (17-31 Jan 2000)500014 RIFHogtown Cr. (2-14 Feb 2000)600018 RIFA (mono)Power line right of waySanders Farm (16-28 Feb 2000)700017 RIFMorrill Farm (1-13 Mar 2000)700017 RIFA (mono)UF Gardens (5-23 May 2001)1100~25 RIFA Natural Area (~10-24 Aug 2001)�6000~35 RIFA (poly)UF Beef Res. Unit (7-14 Sept 2001)180025 RIFA (poly)Ball Farm, Cleveland (15-29 Apr 2000)450035 HIFA (mono)Hilly cattle pasture, well drained, rockyAmes Plantation (31 May-20 Jun 2000)~400027 BIFA (mono)~400023 HIFA (mono) Graham et al.: Fire Ant Decapitating Fly337(Porter et al. 2003) because we were able toout unduly disturbing the mounds and thus, elim-each day. More importantly, several trials withadult ßies, including the release at the UF Gardensite, were not particularly successful. Most of theßies tended to drift away from disturbed moundsThe search for Þeld-reared ßas initiated on June 9, 2000, about 30 days afterthe Þrst ßies were parasitized in the lab. Subse-quent visits were made to the site on June 13, 15,20 and 27 and July 5, 10, 11, 14, and 18, but noßies were observed on any of these trips. All visits1300 and 1500 hours, except for June 9 when thesite was visited at 1000 hours. Observations wereconducted for up to one hour. The site was not vis-ited again until August 14 when the Þrst Þeld-reared ßies were observed and collected (5 total, 3collected). These ßies were positively identiÞed ason August 28 and September 14 and 27. Fliesthe September observations.In 2001, ßies were Þrst observed on May 4, ap-leased (5 ßies over 2 mounds). Flies were sightedagain on May 7. Sites were visited on May 10 and24, but ßies were not found again until July 5 (3On August 16, phorid ßies were located at 8 of12 mounds sampled at the release site. Flies wereFlies were not found at sites 0.2, 0.8 and 1.6 km tothe south of the release site.In July, 2002, ßies were numerous at the re-lease site. On July 15, ßies were located 3.4 kmnorth of the release site. Sites 3.6 and 4.0 kmnorth of the release were searched, and no ßieswere found. However, ßies were found at thesetwo sites on July 17, but not at sites 6.3 and 7.2km north of the release. By July 25, the ßies werefound 11.2 miles north at the Talladega Super-speedway. Flies were located 4.8 km south of therelease on July 16, but were not found 5.6 or 7.9km south of the release. Sites 7.9 and 8.0 kmsouth of the release were devoid of ßies on August5 and September 4. On July 17, ßies were foundalladega National Forest and may have spreadfurther in this direction. Gates across the forestroads were locked and we were not able to gainaccess to search further. One site 7.4 km west-southwest of the release did not have any ßiespresent on this date. Flies were located 19.3 kmnortheast of the on July 18, but were not seen21.2 or 21.7 km northeast of the release. Temper-to 36.6¡C and activity was observed from 800hours until 1600 hours.Florida and Tennessee SitesÞeld-reared ßies at 4 of 7 Florida sites. However,tial releases. In Tennessee, no ßies were recov-ered from the Þeld at all. Almost all of the hybridtures in November and December of 2000. Thisrecord cold may also have been responsible for thefailures at the other two sites.ßies in Ala-bama, where the lent species, was successful. The ßies wereDecember on record in Alabama. Despite theseharsh environmental conditions, ß 86(3)September 2003and 9.0 km southeast of the release site. This iscies against Þre ants (Porter et al. 2002).in Florida and Tennes-see were not successful. The reasons for these fail-ures are not certain, but the success rate (1/11)as much lower than that experienced for in Florida (Porter et al. 2003) and otherstates (Graham et al. 2001). A likely possibilitythat the ßy biotype released was not viable on redthis biotype was adapted to black Þre ants in theBuenos Aires region of Argentina where theywere originally collected. Laboratory testsshowed this ßy biotype had a strong preferencefor black and hybrid Þre ants even though theyants as blacks and hybrids (Porter & Briano2000). Perhaps in the Þeld, this biotype was un-well as it did hybrids in Alabama. In other words,this biotype may have been functionally too hostants even though it is much less speciÞc with species in the laboratory (Porter 2000)(Gilbert & Morrison 1997; Porter& Alonso 1999). Nevertheless, recapture of sev-the Florida sites (Porter et al. 2003) could alsohave been a factor. However, in Tennessee with hybrid and black Þre ants alsofailed. Heavy winter kill of almost all of the hy-the Madisonville, TN site. Although no ßies hadbeen recovered prior to November 2000, therecord cold temperatures may have contributed tofailures at the other two sites.It is also possible that the release techniquesneed improvement. Perhapsbetter than releasing parasitized workers, evenßies do not stay over disturbedßies do. Curiously,successful Talladega site than were released atmost of the unsuccessful sites. The successful re-lease site near Talladega, AL had areas of verydense waist-high grass and areas of damp soil.The other release sites may have been too hot and species.Apparently, Florida (Porter et al. 2003). However, impacts of successful release site near Talladega, Alabama.sissippi in spring of 2002 and by spring 2003, ßies(Vogt & Street 2003; pers. comm.). as also released at four sites in Ala-bama and two sites in Tennessee late summer of2002 and spring 2003. Flies have been recoveredfrom one site in Alabama and one site in Tennes-see (pers. comm.).attacking in northern Argentina (nearville, FL. Hopefully, this new biotype of ants in Florida than the Buenos Aires biotype.H. D., and A. K. were funded by grants from theAlabama Department of Agriculture and Industries.uan Briano (USDA-ARS, SABCL) and David Williams(USDA-ARS, CMAVE) located the site near Las Flores,lected. Juan Briano and Lloyd Morrison (Univ. Texas,Austin) assisted S. D. Porter in collecting ßies at this siteand Juan Briano shipped them back to the U.S. R. K.ander Meer (USDA-ARS, CMAVE) identiÞed hybridÞre ants from Alabama using gas chromatography. VickyBertagnolli, Nicole Hanna, and Catherine Stanton (Au-burn University, AL) assisted with various aspects ofthis study in Alabama. Mike Duke and Greg Myrick pro-vided farm land in Talladega County. Lloyd Davis andLloyd Morrison (USDA-ARS, CMAVE) conducted mostof the Þeld releases of ßies in Florida. K. M. Vail, D.Bailey, and S. S. James (Univ. of Tenn., Knoxville) as-sites. M. Shiers (Univ. of Tenn.) collected ants and did re-leases at Ames Plantation. K. Flanders (Auburn Univ.) isAlabama. Demian Kondo (Auburn University, AL)1981. Techniques for1999. Phorid para-Isolenopsis richteriunder different availability of food in Argentina.Ecol. Entomol. 24: 163-173.2002. Developmental rates and Graham et al.: Fire Ant Decapitating Fly339, D. P. 1990. Approaches to biological controlof Þre ants in the United States, pp. 620-27. R. K.ander Meer, K. Jaffe and A. Cedeno (eds.), AppliedMyrmecology: World Perspective () Westview Press,Boulder, CO., S. D. 1998a. Host-specific attraction of , S. D. 1998b. Biology and behavior of , S. D. 2000. Host specificity and risk assess-Solenopsis richteri1985. Biochemical evidence for hybridization inÞre ants. Florida Entomol. 68: 501-506.Pseudacteon cur-