Attempts to control red imported fire ants in the USA and Australia

摘要

ATTEMPTS TO CONTROL RED IMPORTED FIRE ANTS IN THE USA AND AUSTRALIA The red imported fire ant (Solenopsis invicta) lives up to its name ndash;lsquo;invictarsquo; means lsquo;not having been overcomelsquo; in Latin. Researchers around the world are battling to control this damaging pest. Appearance in 2001 Fire ants (Solenopsis invicta) were first discovered in Brisbane in February 2001. They came to the attention of authorities after two reports arrived on the same day from separate parts of Brisbane. One was from Fisherman Islands the site of container facilities at the mouth of the Brisbane River. A workman had been bitten by ants and a sample was sent to the Commonwealth Scientific and Industrial Organisation (CSIRO). The other incident involved a keen gardener at suburban Richlands in south-west Brisbane who was having problems with ants and gave a sample to local DPI officers.Keith McCubbin director of the Queensland Fire Ant Control Centre believes the pest broke through quarantine into Queensland on two separate Pesticide Outlook ndash; June 2002 105 This journal is copy; The Royal Society of Chemistry 2002 Skin pustules caused by fire ants. Photo Department of Primary Industries Queensland Australia. systems in equipment as varied as computers swimming pool pumps cars and washing machines. They can cause short circuits and fires. Fire ants also have a significant environmental impact. They are aggressive and kill frogs lizards and small mammals. Then there is the impact on agriculture; they damage seeds and crops mounds interfere with equipment they deter hand labour and they damage irrigation equipment.Australia Know your enemy Red Imported Fire Ants Solenopsis invicta are stinging insects that belong to the same order as bees and wasps. They originate in South America and now infest more than 320 million acres in the southern United States and the Brisbane area of Queensland Australia where it has become a coniderable agricultural pest and a significant health hazard. The most significant problem associated with fire ants is their stinging behaviour. The ants are very aggressive and will readily attack anything that disturbs their mound. After firmly grasping the skin with its jaws the fire ant arches its body as it inserts its rear-end stinger into the flesh injecting venom from the poison sac.It often pivots at the head and inflicts an average of seven to eight stings in a circular pattern. Fire ant venom is unique because of the high concentration of proteins and alkaloids which are responsible for the burning pain characteristic of fire ant stings. To look at fire ants are innocuous but appearances are deceptive. They breed and spread rapidly. They have a painful sting that results in a pustule and intense itching which can persist for more than a week. Some people are allergic to the sting and in rare cases can die. They are also a threat to infrastructure. Fire ants are attracted to electrical Fire ants. Photo Scott Bauer. Courtesy of USDA-ARS. DOI 10.1039/b205183b FIRE ANTS FIRE ANTS occasions but admits that fire ants could have been in Australia for 3ndash;5 years ahead of their discovery.Six months after the red imported fire ant was discovered in Brisbane a AU$123 million five year effort has commenced to wipe the species out from Australia. Uncontrolled the ant could spread up to 600,000 square kilometres over the next 30 years. The Australian Bureau of Agriculture Resources Economics has estimated the projected cost to the rural economy of unchecked spread of fire ants could be more than $8.9 billion over the next 30 years inflicting damage to livestock and crops if it is left unchecked. Eradication campaign Fire ants have now been discovered in 730 sites in Brisbane. The sites are largely confined to two areas ndash; Brisbanersquo;s south-west suburbs and Fisherman Islands (the site of container facilities) at the mouth of the Brisbane River.The confinement of outbreaks gives authorities hope the pest outbreak can be eradicated. All governments ndash; federal state and territory ndash; have contributed funds to the AU$123 million fire ant eradication campaign. Around 35,000 hectares in Brisbane will be treated with baits containing S-methoprene or pyriproxyfen ndash; insect growth regulators which work by preventing ant larvae from developing into adults whether there is a visible fire ant nest or not. More than 500 people are working on the national fire ant eradication campaign. Over 400 officers are designated field workers applying the bait. Each property in the treatment zone will be treated 4 times each year for 3 years.There are 3 methods of application ndash; on foot vehiclebased for the more rural residential and industrial blocks with a machine-driven spreader and aerial for large open spaces. Fire ants should be easy to eradicate since they respond well to baits and the baits are effective. Because of genuine concerns in relation to chemical sensitivities a small proportion of homeowners are denying treatment of their property. These properties are being inspected in lieu of treatment. However if ants are found these properties also need to be treated preferably using non chemical means. Failing that the owners are relocated and treatment undertaken. Some wildlife may have to be sacrificed as part of the campaign but once the fire ants are gone and baiting has finished the authorities believe the natural balance will be restored.Mr McCubbin says the campaign team has begun cataloguing rare and endangered species and is looking at breeding programs so that when baiting is finished they can be put back into the environment. Baiting is only a part of the eradication campaign. Surveillance buffer zones have been identified 5 10 and 15 kilometres from the infested areas. For the next 3 years ground surveillance will be carried out in the entire 5- kilometre buffer zone. Targeted inspections will take place in the other zones. The campaign has constant monitoring and surveillance to check that the baits are eradicating fire ants. The fire ant treatment phase should be completed by June 2004.Then itrsquo;s monitoring and validation work until June 2006 ndash; then it will be known if the ldquo;invinciblesrdquo; are as tough as feared. 106 Pesticide Outlook ndash; June 2002 For more information on red ants in Australia see http://www.dpi.qld.gov.au/fireants/ http://www.agric.wa.gov.au/ento/fire_ants.htm http://www.uq.edu.au/entomology/fireant.html USA The fire ant has swept onto the American landscape with an ever-increasing impact. It now infests more than 318 million acres in 12 southeastern states and Puerto Rico. Recently populations have also become established in California and New Mexico. One of the principal laboratories involved in the fight against fire ants is the USDA-ARS Centre for Medical and Veterinary Entomology (CMAVE) based at Gainesville in Florida.There scientists are researching various methods of biological control in addition to the use of chemicals (often in IPM programmes) and semiochemicals. Microsporidia The microsporidium Thelohania solenopsae is a pathogen that causes the slow demise of a fire ant colony. It is one of the most common pathogens of fire ants in Brazil and Argentina. In 1996 during a survey for pathogens in imported fire ant colonies in the U.S. this microsporidium was found in worker ants of the red imported fire ant in Florida Mississippi and Texas. In the first field study initiated in Florida in 1997 T. solenopsae had spread extensively and resulted in 62 maximum reduction in fire ant populations.Field inoculations of T. solenopsae were initiated in 1998 and 1999 in small plots in 10 southern states and infections have been detected in 7 of the 10 states. In addition they have seen limited spread after 1 to 11/2 years. Also T. solenopsae infections were found in 80 of the winged Thelohania solenopsae a microsporidium used against fire ants. Photo David Williams. Courtesy of USDA-ARS. reproductives collected from mating flights. In 1998 the first monogyne colonies were inoculated in a field site in Florida and infections were detected and the disease had spread to other colonies at the site in 1999. This was the first evidence of spread of T. solenopsae in a monogyne population of fire ants. The impact of this pathogen on imported fire ant populations in the U.S.is being studied and results should be available in 2ndash;3 years. In addition both laboratory and field studies are underway with another microsporidian Vairimorpha invictae. When this pathogen is added to a colony infected with T. solenopsae the result is a quicker demise of fire ant colonies. Research with both pathogens is continuing in the U.S. and in Argentina at the USDA-ARS South American Biological Control Laboratory in Hurlingham Argentina by Juan A. Briano. Parasitic ants Solenopsis daguerrei is a parasitic ant of imported fire ants. This parasite produces no worker caste and is totally reliant on its host colony for its care. Having no worker caste only reproductive males and females represent this species.S. daguerrei will attach themselves to queens of the black and red imported fire ants Solenopsis richteri and S. invicta respectively and divert resources from the host queen(s). In addition the host colony also feeds and maintains the brood of S. daguerrei. Thus S. daguerrei is a potential stress factor of fire ant colonies. Field studies and observations of the impact of S. daguerrei on the fire ant S. richteri are being conducted in sites located in Argentina by Juan A. Briano amp; Luis A. Calcaterra at the USDA-ARS South American Biological Control Laboratory in Hurlingham Argentina. Average percent parasitism from pastures located at 21 sites was 5.1. Mound densities were 33 less in sites with S. daguerrei and the number of fire ant queens was 47 less in parasitized colonies.Phorid flies Research is focusing on the use of phorid decapitating flies in the genus Pseudacteon as biocontrol agents for imported fire ants. One species (Pseudacteon tricuspis) has been released in Florida and several other states. This fly is South American phorid fly Pseudacteon. Photo Sanford Porter. Courtesy of USDA-ARS. FIRE ANTS permanently established at 8ndash;10 sites and populations are beginning to expand rapidly out of several release sites. To determine the impacts of these flies on fire ant populations Dr. Sanford Porter and Dr. Lloyd Morrison are establishing an extensive field monitoring program that is funded by a USDA-NRI research grant. They expect results from this research program in the next 2ndash;3 years.Chemical control In addition to research on biological controls CMAVE scientists are developing integrated pest management (IPM) strategies for imported fire ant control. This entails research to determine the most effective way to utilize commercially available fire ant baits assessing the efficacy of new products and integrating biological and chemical controls. Control strategies are also being developed for fire ants in sensitive areas such as recreational areas and fish farms. Semiochemicals Semiochemicals play a central role in the functioning of social insect colonies affecting many important processes including defense nestmate recognition recruitment alarm mating flight activities development and reproduction of colony members.These compounds and the physiological processes underlying their biosynthesis and mode of action hold great promise for use as effective biologically-based regulators to control populations of imported fire ants and other social insect pests. New areawide pest management project One of the most recent ARS-funded areawide projects which began in May 2001 is part of a long-fought campaign to control the red imported fire ant Solenopsis invicta. The Areawide Suppression of Fire Ant Populations in Pastures is a partnership among ARS the USDArsquo;s Animal and Plant Health Inspection Service the University of Florida and Texas Aamp;M Oklahoma State and Clemson Universities. The goal of the project is to demonstrate how to reduce fire ant populations to very low levels by combining strategic pesticide applications with two self-sustaining biocontrol agents from South America the fire ant-decapitating fly Pseudacteon tricuspis and the pathogen Thelohania solenopsae. As scientists introduce these agents fewer subsequent bait toxicant treatments should be needed to maintain fire ant control. Diverse demonstration sites as large as 640 acres in the three states were chosen to represent the range of the fire antrsquo;s infestation. ARS will direct the major activities of the four land-grant universities and other organizations associated with the project for 5 years. ARS will also add a site in Mississippi in 2002. For more information on fire ants in the U.S. see http://cmave.usda.ufl.edu/~ifahi/index.html http://cmave.usda.ufl.edu/~formis/ http://fireant.tamu.edu/index.html http://www.ento.okstate.edu/fireants/fireants.html http://www.ceris.purdue.edu/napis/pests/ifa/ http://ipmworld.umn.edu/chapters/lockley.htm Pesticide Outlook ndash; June 2002 107