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Home , Black imported fire ant, Caenocholax, Fire ant, Lipotrophidae, Orasema, Pseudacteon

ENTO-008 03/14

Potential Biological Control Agents for the Red Imported

Bastiaan M. Drees and establishing native natural enemies into Extension Entomologist Emeritus areas, or mass-rearing and releasing new exotic A&M AgriLife Extension Service natural enemies. This last approach is known as Robert Puckett importation biological control. Associate Research Scientist Texas A&M AgriLife Research The first step is to search for promising natural enemies in the ant’s native home, considering for importation and release in the The red imported ,Solenopsis invicta only natural enemies that specifically attack the Buren (: Formicidae), arrived in . Native ant compete the United States from with with imported fire for food and can reduce few parasites or pathogens that regulate the imported fire ant populations through competi- ant’s populations (Wojcik 1998), (see Natural tion for resources. Some native ants also attack Enemies of Fire Ants). This lack of natural ene- and kill young fire ant queens as they begin to mies is one factor that has allowed the ant to establish colonies in new territories. spread and dominate resources in its non-native The importation of exotic natural enemies must range (Porter 1998). Fire ant densities are many be approved by the United States Department of times greater in the United States than in South Agriculture– and Plant Health Inspec- America where a variety of natural enemies tion Service (USDA–APHIS). Once approved for attack this pest. Attempts are currently under- importation and release in the United States, the way in the United States to augment natural exotic natural enemy is reared in large numbers and enemies in order to reduce its impact. released at multiple locations over several years. The goal of importation biological control is to establish How Is Biological Control permanent and effective populations of the exotic natural enemy to eliminate the need for further ccomplished A ? mass-rearing and release, which is expensive. Biological control of pest organisms relies on Some imported natural enemies may be effective keeping native natural enemies, introducing but fail to establish permanent populations. Other native natural enemies may already be present Natural Enemies of the in the United States but occur in numbers too ed mported ire nt small to provide effective control. In these cases, R I F A it may be possible to mass-rear the native natu- The following is a list of parasites, pathogens, ral enemy and periodically release it to increase and predators under study for potential use as the level of biological control. This activity is biological control agents. Most are in the early augmentation biological control. stages of research. A few species have been This approach requires rearing procedures that released in limited numbers under controlled maintain the genetic characteristics necessary conditions and some have established and for the natural enemy to be effective when spread. released in the field. Some natural enemies, Microsporidia especially pathogens, may be formulated and applied much like an insecticide and are some- Kneallhazia solenopsae (Formerly Thelohania times called . solenopsae). K. solenopsae is a microscopic pro- tozoan that infects immature and adult fire ants. Infected ants, including queens, have shorter How Does Biological Control life spans, and, over a period of several months Work? to a year, the colony declines in size and vigor. Presumably, diseased ants moving between Parasites, pathogens, and predators can impact multiple-queen colonies transmit the pathogen. fire ant populations directly by killing ants or K. solenopsae attacks only the exotic red and indirectly by making them less competitive with the although there is an native ants for available resources. Native ants unconfirmed report of a similar strain detected compete with red imported fire ants for food. in Solenopsis geminata, the tropical fire ant. Also, some native ants feed on fire ant queens and can eliminate colonies before they are established In Argentina, about 20 percent of the red or while they are still small. Most of our native ant imported fire ant colonies are infected. Sur- species cannot compete effectively with fire ants. veys in the Unites States did not detect this If imported natural enemies reduce the fire ant’s disease organism until 1996, when it was dis- ability to compete for food, disperse, or reproduce, covered in . Since then, K. solenopsae then native ant species may gain a competitive has also been found and/or released in most fire edge and begin to suppress fire ant densities. ant infested southeastern states (Milks et al. 2008). Research is underway to discover ways to It takes a combination of several natural ene- increase the impact of this pathogen and culture to shift the competitive and ecological mies it in the laboratory and the field (Williams et al. balance in favor of the native ants. Establishing 1999). There is also evidence that in areas where new exotic enemies and developing methods for insecticides were used to clear fire ants, infected augmenting native natural enemies of the red fire ant populations will not re-infest areas as imported fire ant require long-term commit- quickly as uninfected populations will (Vander ments to research and development. Even then, Meer et al. 2007, Oi et al. 2008). natural enemies alone will not control fire ants. Rather, biological control will be one part of Fungi an program that integrated pest management Beauveria. , a common includes selective insecticides, cultural practices, fungus, attacks many species. A strain of and other control methods (see What is IPM? Beauveria that attacks the imported fire ant was and USDA Agricultural Research Areawide Fire reported from Brazil in 1987. This fungus pro- Ant Suppression).

2 duces microscopic spores that attach to the ant’s stage of attack, the maggot consumes all of the body, germinate, and grow inside the ant, feed- head’s contents. Pupariation, the onset to the ing on its internal organs. When the ant dies, larval-pupal transition, occurs in the severed its body becomes filled with fungal growth. The head capsule and the adult emerges from the fungus sometimes grows outside the dead ant, ant’s head about 3 weeks later. covering it with a white, fuzzy growth. Studies Typically, rates in infested colonies have shown that when B. bassiana is applied only reach 1 to 3 percent of workers, and this to the , it is much less effective than if the alone has little impact on fire ant numbers. The spores are applied directly to the ants. The appli- ’ effect on ant behavior is more important. cation of B. bassiana to fire ant baits has been Fire ant workers quickly recognize when phorid investigated, but a commercially formulated flies are present and either attempt to escape product has yet to be introduced to the market underground or assume a defensive posture. (Bextine & Thorvilson 2002). The presence of only 3 to 4 flies is sufficient to Metarhizuim anisopliae Aspergillis spp. (see disrupt ant activity. Fungi as Biocontrol Agents) As a result, ants attacked by phorid flies spend Virus (see Viruses as Biocontrol Agents) less time searching for food. Native ant spe- Parasitiods cies, which are not attacked by the phorid flies, benefit by the greater food resources available Phorid flies. Phorid flies ( spp.) are to them. Thus, the reduction in food collection small flies that parasitize ants, including fire and increased competition from native ants has ants. The adult flies are about 1/16 inch long a much greater negative impact on a fire ant and fly rapidly. They hover above disturbed fire colony than does the death of a small percentage ant mounds or along foraging trails, waiting for of worker ants from parasitism. Red imported an opportunity to swoop down and parasitize fire ants respond similarly to introduced phorid workers by depositing an egg into them. Once in flies, whether in the United States or their native the ant, the egg quickly hatches into a tiny mag- South America. got. The maggot feeds inside the ant for about 3 weeks before the parasitized ant dies. The ant’s About 20 species of Pseudacteon in Brazil and head falls from its body as produced by Argentina attack the red imported fire ant and the parasite dissolve the connective tissue that several of these species have been evaluated, attaches the head to the body. During the final mass-reared, and released in the United States (Callcott et al. 2011). It is expected that those phorid species that attack ants foraging for food will be more effective than those fly species that attack ants only at disturbed mounds. Six Sole- nopsis-attacking phorid fly species have been released and established in the United States: , P. curvatus, P. obtusus, P. litoralis, P. nocens, and P. cultellatus (Gilbert et al. 2008, Plowes et al. 2011, Porter et al. 2011). Parasitic ant. Solenopsis daguerri is an unusual ant species that takes control of the fire by parasitizing the fire ant queen or queens (see Parasitic Ants as Biocontrol Agents). The parasitic ant enters the fire ant colony and

3 is not killed because it produces the same pher- about 1 to 2 percent of the fire ants in a colony omone (chemical signals) that fire ants use to are parasitized by C. fenyesi. recognize their fellow nest mates. The parasitic Orasema. Species of Orasema (Eucharididae) ant seeks out a fire ant queen, crawls on top of are tiny that parasitize immature ants, her, and grasps her tightly with its legs and jaws, including fire ants (seeDistribution, abundance thereby “yoking” the imported fire ant queen. and persistence of species of Orasema (Hymenop- A fire ant queen can become “yoked” by two or tera: ) parasitic on fire ants in South three parasitic queen ants. Each parasite pro- America). Female Orasema wasps lay large num- duces queen that allow it to mas- bers of eggs on plant leaves and buds. The eggs querade as a fire ant queen. Thus deceived, the hatch into tiny flattened larvae called planidia. worker fire ants proceed to feed the parasite and They lie in wait and attach to passing ants. Once tend the eggs it produces. The fire ant queen, left in the ant colony, the planidia leave the worker untended by the workers, gradually stops laying ant, attach to ant larvae, and consume their eggs and starves to death. Fire ant workers rear hosts after pupation begins. Typically, Orasema the parasitic ant eggs and soon the fire ant col- kills a small percent of fire ants. Several species ony becomes a colony of parasitic ants. Emerging of Orasema parasitize the imported fire ant in parasitic ants, which are all queens (no worker South America, and several other species of ants are needed) leave the colony in search of Orasema occur in the United States. Research is new fire ant colonies to parasitize. In South underway to learn more about these ant para- America, the parasitic ant is present in about 1 to sites and to develop mass-rearing techniques. 4 percent of fire ant colonies. The parasitic ant is not currently in quarantine in the United States Nematodes and . Certain nematodes and researchers are developing methods to rear ( carpocapsae and Heterorhabditis sufficient numbers of the parasite for eventual species) attack and parasitize red imported fire release across the North American fire ant range. ants and other (see Natural, Organic, and Alternative Methods for Imported Fire Ant . Strepsiptera are minute insects Management). Ants in treated colonies often that parasitize other insects. One species, leave the nesting site or mound and move to a Caenocholax fenyesi, attacks the red imported new location (Drees et al. 1992). However, field fire ant in the United States (Cook et al. 1997, evaluations of commercially available species/ 1998). Like other Strepsiptera, C. fenyesi has a strains of these parasites currently being mar- complex and unusual life cycle. The female para- keted for fire ant control have not yet been con- sitizes a species of bush , Hapithus agita- ducted to demonstrate their effectiveness. tor. Once the immature parasite has consumed the cricket, she develops into the adult stage. Pymotes sp. The straw itch , Pymotes tritici, However, the adult female never leaves the dead is a native external mite parasite of insects and cricket. Rather, she produces thousands of eggs does not normally attack fire ants. However, that hatch into larvae called triungulins. The when applied in large numbers to fire ant col- tiny, flattened triungulins leave the female and onies under laboratory conditions, straw itch search for new hosts. While female triungulins mites will feed on immature ants. Published must find another bush cricket, male triungulins field research evaluating commercially available develop in fire ant adults. Once a male triun- straw itch mites applied as directed to fire ant gulin attaches to a passing fire ant, it burrows colonies have reported insignificant levels of into the ant to feed and develop. Parasitized control (Thorvilson et al. 1987). Moreover, the fire ants typically climb to a high perch where straw itch mite is widely regarded as a pest and, they soon die. The adult male Strepsiptera then as its name implies, can cause skin irritation in emerges from the dead fire ant. In Texas, only humans.

4 ThePymotes mite and parasitic nematodes have been available for sale as individual mound Parasitic fly. Pseudacteon spp. (Diptera: Phori- treatments. Their high cost may prohibit large- dae). Larvae are internal parasitoids, but few scale use. Also, their effects, if any, are gener- (1 to 3 percent) of the ants are parasitized. ally limited to the treated ant colonies and are Egg-laying attempts by adult flies prevent not expected to persist in the environment or daytime ant foraging behavior, providing spread from colony to colony. However, addi- time for native ants to forage. tional research may improve nematode and mite strains and delivery methods to make them Parasitic ant. Solenopsis daguerri. (Hymenop- effective biological control agents. tera: Formicidae). Workerless, obligate para- sitic ant (cannot complete its life cycle with- out a suitable host). Some Potential and Natural Enemies of Red Imported Fire Ants Strepsiptera. Tiny insect parasitoids of fire ants. Parasitic . Orasema spp. (Hymenoptera. Pathogens Eucharitidae). Females lay eggs on plant Microsporidia tissue. After the eggs hatch, the planidia (first Kneallhazia (Thelohania solenopsae) (Protozoa: stage larvae) are phoretic on worker ants Microspora: Thelohaniidae). Produces large (they use fire ants as a mode of transport). cysts in adult ants; found in adult and imma- In the nest, planidia feed externally on ant ture ants. pupae and kill the ant in the pupal stage. Vairimorpha invictae (Protozoa: Microspora: Nematodes. Tetradonema solenopsis (Nem- Burenellidae). Does not produce cysts; found atoda: Mermithoidea: ). in adult and immature ants. Commercially available species include Stein- ernema caropcapsae and Heterorhabditis Protozoa heliothidis. geminata (Protozoa: Neogregarinida: Mites. ventricosus (Acarina: Pyemoti- Lipotrophidae). Spores found in immature dae). Common in the United States. These fire ants and infected individuals die in the mites are not normally found attacking fire pupal stage. ants but will feed on fire ants if applied in Fungi large numbers. Beauveria bassiana (Fungi: Deutero-mycotina). Predators (also see Predators) A strain of this common fungus grows inter- Several different kinds of insects live in fire ant nally in adult fire ants and kills them. colonies and feed on immature ants. These (Fungi: Deutero-my- include species of (, cotina). A strain of this common fungus and Chrysomelidae), true bugs grows internally in adult fire ants and kills (: Lygaeidae) and silverfish (Thysa- them. nura). None of these are being considered at this time as biological control agents. Aspergillis spp. (Fungi: Deutero-mycotina). A strain of this common fungus grows inter- nally in adult fire ants and kills them. Literature Cited

Virus (picorna-like virus) Solenopsis invicta virus Bextine, B. R. and H. G. Thorvilson. 2002. (SINV-1), (see Viruses as Biocontrol Agents). “Monitoring Solenopsis invicta (Hymenoptera:

5 Formicidae) Foraging with Peanut Oil-Baited, Oi, D. H., D. F. Williams, R. M. Pereira, P. M. UV-Reflective Beauveria Alginate Pellets.” Horton, T. S. Davis, A. H. Hyder, H. T. Bolton, Southwestern Entomologist 27(1): 31–36. B. C. Zeichner, S. D. Porter, A. L. Hoch, M. L. Boswell, and G. Williams. 2008. “Combining Callcott, Anne-Marie, Sanford D. Porter, Ron D. Biological and Chemical Controls for the Man- Weeks, L. C. “Fudd” Graham, Seth J. Johnson, agement of Red Imported Fire Ants (Hymenop- L. E. Gilbert. 2011. “Fire Ant Decapitating Fly tera: Formicidae).” Amer. Entomol. 54:46–55. Cooperative Release Program (1994–2008): Two Pseudacteon Species (P. tricuspis, P. curvatus) Plowes, R. M., P. J. Folgarait and L. E. Gilbert. Rapidly Expand Across Imported Fire Ant Popu- 2011. “The Introduction of the Fire Ant Para- lations in the Southeastern United States.” sitoid Pseudacteon nocens in North America: J. Insect Sci. 2011. 11.19. Challenges When Establishing Small Popula- tions.” BioControl DOI 10.1007/s10526-011- Cook, J. L., J. S. Johnston, S. B. Vinson, and R. E. 9428-9. Gold. 1997. “Distribution of Caenocholax fenyesi (Strepsiptera: ) and the Habi- Porter, S. D. 1998. “Biology and Behaviour of tats Most Likely to Contain its Stylopized Host, Pseudacteon Decapitating Flies (Diptera: Phori- Solenopsis invicta (Hymenoptera: Formicidae).” dae) that Parasitize Solenopsis Fire Ants (Hyme- Environmental Entomology, 26(6): 1258–1262. noptera: Formicidae).” Florida Entomol. 81(3): 292–308. Cook, J. L., S. B. Vinson, and R. E. Gold. 1998. “Developmental Stages of Caenocholax fenyesi Porter, S. D., L. C. Graham, S. J. Johnson, L. G. Pierce (Strepsiptera: Myrmecolacidae): Descrip- Thead, and J. A. Briano. 2011. “The Large Decap- tions and Significance to the Higher itating Fly Pseudacteon litoralis (Diptera: Phori- of Strepsiptera.” International Journal of Insect dae): Successfully Established on Fire Ant Popula- Morphology and Embryology, 27(1): 21–26. tions in .” Florida Entomol 94:208–213. Drees, B. M., R. W. Miller, S. B. Vinson and R. Porter, S. D. and L. E. Alonso. 1999. “Host Spec- Georgis. 1992. “Susceptibility and Behavioral ificity of Fire Ant Decapitating Flies (Diptera: Response of Red Imported Fire Ant (Hymenop- ) in Laboratory Oviposition Trials.” tera: Formicidae) to Selected Entomogenous J. Econ. Entomol. 92(1): 110–114. Nematodes (Rhabditida: Steinernematidae & Het- Thorvilson, H. G., S. A. Philips, Jr., A. A. Soren- erorhabditidae).” J. Econ. Entomol. 85(2): 365–370. son and M. R. Trostle. 1987. “The Straw Itch Gilbert, L. A., C. L. Barr, A. A. Calixtro, J. L. Mite, (: ), as a Cook, B. M. Drees, E. G. LeBrun, R. J. Patrock, Biological Control Agent of Red Imported Fire R. M. Plowes, S. D. Porter, R. T. Puckett. 2008. Ants, Solenopsis invicta (Hymenoptera: Formici- “Introducing Phorid Fly Parasitoids of Red dae).” The Florida Entomol. 70 (1): 440–444. Imported Fire Ant Workers from South Amer- Vander Meer, R. K., Pereira, R. M., Porter, S. ica to Texas: Outcomes Vary by Region and by D., Valles, S. M. and Oi, D. H. 2007. “Areawide Pseudacteon Species Released.” Southwestern Suppression of Invasive Fire Ant Populations.” Entomologist 33(1): 15–30. Proceedings of the International Conference on Milks, M. L., J. R. Fuxa and A. R. Richter. 2008. Area-Wide Control of Insect Pests, IAEA 2005. “Prevalence and Impact of the Microsporidium Williams, D. F., D. H. Oi, and G. J. Knue. 1999. Thelohania solenopsae (Microsporidia) on Wild “Infection of Red Imported Fire Ant (Hymenop- Populations of Red Imported Fire Ants, Solenop- tera: Formicidae) Colonies with the Entomo- sis invicta, in .” Journal of Invertebrate pathogen Thelohania solenopsae (Microsporidia: Pathology 97:91–102. Thelohaniidae).” J. Econ. Entomol. 92: 830–836.

6 Wojcik, D. P. 1998. “Survey of Biological Control Viruses as Biocontrol Agents Agents in Brazil—A Final Report, with Com- www.ars.usda.gov/Research/docs.htm?docid= ments on Preliminary Research in Argentina.” 9050 in Proceedings of the 1998 Imported Fire Ant Parasitic Ants as Biocontrol Agents Conference, Athens, GA, pp. 50–61. http://www. www.ars.usda.gov/Research/docs.htm?docid= extension.org/sites/default/files/w/3/38/1998_ 8981 IFA_Conference_Proceedings.pdf Distribution, abundance and persistence of species of Orasema (Hymenoptera: Eucharitidae) Acknowledgments parasitic on fire ants in South America Originally written by Bastiaan M. Drees and naldc.nal.usda.gov/catalog/46163 A. Knutson, this fact sheet was released in Natural, Organic, and Alternative Methods for May 1998 and revised in 2002. Sanford Porter, Imported Fire Ant Management Harlan Thorvilson, and S. Bradleigh Vinson u.tamu.edu/ento-009 reviewed earlier drafts of this fact sheet. The Viruses as Biocontrol Agents current revision was reviewed by “Fudd” Gra- www.ars.usda.gov/Research/docs.htm?docid= ham and Wizzie Brown. 9050&page=2

References Predators uts.cc.utexas.edu/~gilbert/research/fireants/ Natural Enemies of Fire Ants faenviron/predators.html www.extension.org/pages/30546/natural- Managing Red Imported Fire Ants in Urban enemies-of-fire-ants Areas What is IPM? www.extension.org/pages/11004/managing- landscapeipm.tamu.edu/what-is-ipm/ imported-fire-ants-in-urban-areas-printable- version Areawide Fire Ant Suppression www.ars.usda.gov/sites/fireants/ Broadcast Baits for Fire Ant Control www.agrilifebookstore.org/product-p/e-628 Fungi as Biocontrol Agents www.ars.usda.gov/Research/docs.htm?docid= Fire Ant Control: The Two-Step Method and 9007 Other Approaches www.agrilifebookstore.org/product-p/ento-034

For more information regarding fire ant management, see Extension publications Managing Red Imported Fire Ants in Urban Areas, Broadcast Baits for Fire Ant Control, or Fire Ant Control: The Two-Step Method and Other Approaches posted on http://AgriLifeBookstore.org.

The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Texas A&M AgriLife Extension Service is implied.

Texas A&M AgriLife Extension Service AgriLifeExtension.tamu.edu More Extension publications can be found at AgriLifeBookstore.org Educational programs of the Texas A&M AgriLife Extension Service are open to all people without regard to race, color, sex, religion, national origin, age, disability, genetic information, or veteran status. The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Courts of Texas Cooperating.

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