Guadalupe Rojas, Juan. A. Morales-Ramos, Jian Chen, Michael Grodowitz, and Margaret Allen discuss the hurdles of Biological Control to control the Red Imported Fire Ant.
The red imported fire ant, Solenopsis invicta, is one of the most successful invasive ants and it is regarded as one of the world’s worst invasive alien species (Lowe et al., 2000). Native to South America, S. invicta has been introduced into many countries and regions, including the United States, Australia,
China, the Philippines, Thailand, Taiwan, Hong Kong, Macau, among others (Ascunce et al., 2011). Their spread has been greatly facilitated by the increase of global commerce and the consequent breakdown of biogeographic barriers. Fire ant invasion often causes damage to the environment, human economy and health. For example, over 40 million people in the USA are at risk of being stung by imported fire ants (Drees,1998). In addition to local dermal reactions, fire ant stings are a major cause of serious anaphylactic reactions (Xu et al., 2012). Fire ants attack pets, livestock, and wildlife (Vinson, 2013) and reduce biodiversity, particularly other arthropods (Cook, 2003). Annual economic costs associated with imported fire ants alone reached 6.5 billion dollars in the USA. Management of pest ants has continued to depend heavily on synthetic insecticides despite efforts toward developing alternative control technologies. The red imported fire ant is the number one pest for which homeowners in Texas buy and apply pesticides (Russell, 1999). A solution for alleviating the heavy dependence on synthetic insecticide is to implement
Integrated Pest Management (IPM) strategies that combine different control practices to overcome the shortcomings of individual practices. Biopesticides, pest control agents based on pathogenic micro organisms or toxic natural products, have become a critical component of IPM in recent years (Chandler et al., 2011).
Biological control of fire ants
A tremendous effort has been made over the past few decades to mitigate fire ant problems using biological control agents. These agents include parasitoids, such as phorid flies (Callcott et al., 2011), fungi (Bextine and Thorvilson, 2002), bacteria (Bouwma et al., 2006), microsporidia (Oi et al., 2005), viruses (Valles and Hashimoto, 2009), and nematodes (Brinkman and Gardner, 2000).
Fire ants construct elaborated underground nests which can extend to 2-3m in depth. The underground habitat harbours a multitude of infectious microorganisms which can cause high disease incidence leading to extreme mortality in ant populations. To counter this, fire ants have evolved a number of strategies to combat pathogens (Cremer et al., 2007); among those are grooming and necrophoric (removal of dead bodies from the nest) behaviours, and chemical defences. Active inclusion of antimicrobial plant resins into nest materials affording protection from microbes has also been reported (Schluns et al. 2009). The most studied antimicrobial strategy is the secretion of antimicrobial compounds through various glands most importantly from Dufour glands and its venom. As early as 1958, Blum et al. (1958) documented antimicrobial properties of fire ant venom. Since then hundreds of manuscripts have been published on fire ant venom chemistry detailing various components, biosynthesis, antimicrobial properties, behaviours associated with venom dispersal, incorporation in nest materials, among others (Vander Meer 2012).
Lastly, internal defence through immune system response is the least studied antimicrobial strategy. Mackintosh et al. (1998) isolated and characterised two antibacterial peptides in Myrmecia gulosa that are synthesised in response to bacterial challenge. Orivel et al. (2001) identified 15 novel peptides from the venom of ant species Pachycondyla goeldii. These peptides, named ponericins, exhibited a defensive/inhibitory role against microbial pathogens arising from prey introduction and/or ingestion.
Ascunce, M.S., Yang, C.C., Oakey, J., Calcaterra, L., Wu, W.J., Shih, C.J., Goudet, J., Ross, K.G., and Shoemaker, D. 2011. Global invasion history of the fire ant Solenopsis invicta. Science 331:1066-106.
Bextine, B.R., and Thorvilson, H.G. 2002. Field applications of bait-formulated Beauveria bassiana alginate pellets for biological control of the red imported fire ant (Hymenoptera: Formicidae). Environ. Entomol. 31:746-752.
Blum, M. S., Walker, J. R., Callahan, P. S., and Novak, A. F. 1958. Chemical, insecticidal, and antibiotic properties of fire ant venom. Science 128:306–307.
Bouwma, A.M., Ahrens, M.E., DeHeer, C.J., and Shoemaker, D. 2006. Distribution and prevalence of Wolbachia in introduced populations of the fire ant Solenopsis invicta. Insect Mol. Biol. 15:89-93.
Brinkman, M.A., and Gardner, W.A. 2000. Possible antagonistic activity of two entomopathogens infecting workers of the red imported fire ant (Hymenoptera: Formicidae). J. Entomol. Sci. 35:205-207.
Callcott, A.M.A, Porter, S.D. Weeks, R.D. Jr., Graham, L.C. Johnson, S. J., and Gilbert, L.E. 2011. Fire ant decapitating fly cooperative release programs (1994-2008): Two Pseudacteon species, P. tricuspis and P. curvatus, rapidly expand across imported fire ant populations in the southeastern United States. J. Insect Sci. 11:19 (available online: insectscience.org/11.19).
Chandler, D., Bailey, A.S., Tatchell, G.M., Davidson, G., Greaves, J, Grant, W.P. 2011. The development, regulation and use of biopesticides for integrated pest management. Phil. Trans. R. Soc. B 366:1987-1998.
Cook, J.L. 2003. Conservation of biodiversity in an area impacted by the red imported fire ant, Solenopsis invicta (Hymenoptera: Formicidae). Bio. Conserv. 12:187-195.
Cremer, S., Armitage, S.A.O., Schmid-Hempel, P. 2007 Social immunity. Curr. Biol. 17, R693-R702. (doi:10.1016/j.cub.2007.06.008). Drees, B.M. 1998. Medical problems and treatment considerations for the red imported fire ant. Texas Agricultural Extension Service, Fire Ant Plan Fact Sheet #023, 8 p.
Lowe, S., Browne, M., Boudjelas, S., and De Poorter, M. 2000. 100 of the World’s Worst Invasive Alien Species: A selection from the Global Invasive Species Database. The Invasive Species Specialist Group (ISSG) a specialist group of the Species Survival Commission (SSC) of the World Conservation Union (IUCN) p.1–12.
Mackintosh, J. A., Veal, D.A., Beattie, A.J., and Gooley, A.A. 1998. Isolation from an ant Myrmecia gulosa of two inducible O-glycosylated proline-rich antibacterial peptides. J. Biol. Chem. 273: 6139-6143.
Oi, D.H., Briano, J.A., Valles, S.M., and Williams, D.F. 2005. Transmission of Vairimorpha invictae (Microsporidia: Burenellidae) infections between red imported fire ant (Hymenoptera: Formicidae) colonies. J. Invertebr. Pathol. 88: 108-115.
Orivel, J., Redeker, V., Le Caer, J.P., Krier, F., Revol-Junelles, A.M., Longeon, A., Chaffotte, A., Dejean, A. and Rossier, J., 2001.
Ponericins, new antibacterial and insecticidal peptides from the venom of the ant Pachycondyla goeldii. J. Biol. Chem. 276: 17823- 17829.
Russell, M.S. 1999. Red imported fire ant control around bodies of water; Texas Agricultural Extension Service, Fire Ant Plan Fact Sheet #021, 2 p.
Schluns, H. and Crozier, R.H., 2009. Molecular and chemical immune defenses in ants (Hymenoptera: Formicidae). Myrmecological News. 12: 237-249.
Vander Meer, R.. 2012. Ant interactions with soil organisms and associated semiochemicals. J. Chem. Ecol. 38: 728-745.
Valles, S.M., and Hashimoto, Y. 2009. Isolation and characterisation of Solenopsis invicta virus 3, a new positive-strand RNA virus infecting the red imported fire ant, Solenopsis invicta. Virology 388: 354-361.
Vinson, S.B. 2013. Impact of the invasion of the imported fire ant. Insect Sci. 20: 439-455.
Xu, Y., Huang, J., Zhou, A., and Zeng, L. 2012. Prevalence of Solenopsis invicta (Hymenoptera: Formicidae) venom allergic reactions in mainland China. Fla. Entomol. 95: 961-965.
Dr. M. Guadalupe Rojas
USDA ARS SEA BCPRU
Stoneville, MS 38776
Tel: 662 686 3070