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Introductory words

	Reasons for controlling fire ants

The imported fire ant is undoubtedly a serious pest in both urban and rural areas causing billions of dollars of economic damage to the U.S. annually. It is estimated that fire ants directly affect the lives of about 40 million people. They often occupy the areas where we work, live and play where they create unsightly mounds and interfere with commerce and industry. They are also known to nest in, and subsequently to damage, electrical boxes such as air conditioning and traffic signals. In addition, the fear of being stung can deter us from carrying out the activities we wish to pursue.

Stings

Fire ants sting together in concerted attacks. They pass complex communication signals between them to achieve an unnerving level of synchronisation.

The affects of the stings can be serious. Some people experience only a local reaction and temporary discomfort but, in most, a swollen red area will occur followed by a sterile pustule within a day or two. Although the venom is antibiotic, secondary infections due to scratching may occur. Reaction to fire ant stings is similar to reaction to the stings of bees, wasps and hornets. The majority of fire ant stings are medically uncomplicated but a small percentage of people stung, perhaps less than .5 percent, experience an extreme anaphylactic reaction. These reactions occur within minutes of a sting and vary in severity. Some individuals may need to go to hospital since the reaction may be life threatening.

The chances of being stung increase in times of drought as the fire ants move into places controlled by or frequented by people in search of water. During a drought, fire ants may be more likely to damage gardens, houses, and golf courses but the threat to agriculture is even more serious.

Effects on farming

The large mounds of the Imported Fire Ants in particular create problems in planting and harvesting crops. The mounds cause damage to combine harvesters and other machinery, hindering mowing operations, and reducing land values in infested areas.

Red Imported Ants will feed on wheat, corn and other seeds including cotton and soybeans reducing yields. The ants may also cause damage to very young plants, ripe fruits and berries. They occasionally attack young, unprotected farm animals such as newborn calves, pigs, newly hatched fowl and young rabbits.

Effects on the ecosystem

Little scientific research into the extent of the impact on wildlife numbers has been carried out but it is strongly suspected that the Imported Fire Ant species have had a negative effect on biodiversity in the southern US. There is much anecdotal evidence of young wildlife being attacked by fire ants; it appears that ants are attracted to moisture in the eyes, nose and mouth of young mammals and in the hatching eggs of ground nesting birds and reptiles. However, competition for seeds and insects may be even more damaging than direct attacks by ants on individual animals. High Imported Fire Ant populations affect loggerhead shrikes, bobwhite quail, horned lizards and many other species in this way.

	The case for the defence

Can anything good be said about such pests? Fire ants are successful predators and can be used by farmers as a biological control for insects, ticks and other small invertebrates that might be harmful to crops. The Red Imported Fire Ant is reported to be a predator of the sugarcane borer, the rice stink bug, the striped earwig, aphids, the boll weevil, the soybean looper, the cotton leafworm, the hornfly , and many other pests. Fire ants are tick predators; normally gardens and farmyards with fire ants do not have ticks and, since ticks carry diseases, this lessens the risks to people and animals. Lone star tick.

	How to kill Imported Fire Ants

Given the damage this aggressive and adaptable insect causes it is not surprising that many feel it is justified to remove species of fire ant from areas to which they are not native. Imported Fire Ant populations in local areas can be greatly reduced by pesticides but these products rarely eliminate all the ants and areas are very rapidly reinfested. Is S. Invicta really invincible?

There are several reasons why the Imported Fire Ant is so good at reinvading the territory from which it has just been cleared.

The imported fire ant has a very high reproductive potential due to the extended mating season and the ability to form multi-queen colonies.

The new queens spread by flying and thus can "drop into" any area allowing a more rapid reinfestation than would be the case with crawling insects.

Fire ants are very competitive and quickly eliminate most other competing ants and other invertebrate predators, which will probably also have been weakened by the pesticides.

It is clear that an alternative to the broadly aimed pesticide must be found and, since 1958, over seven thousand compounds have been evaluated the USDA Agricultural Research Service.

A microbiological approach is unlikely to be successful since fire ants have a filtering system that admits only liquids into their digestive systems and removes bacteria. Some pest controllers therefore advocate a chemical approach and recommend feeding the ants sugar water combined with boric acid or disodium octoborate tetrahydrate for several weeks . An alternative method is the use of insect growth regulators hidden in bait. Neither method has proved effective.

Flooding the mounds is an option but should be carried out only at certain times of the day. During foraging periods, only a small percentage of ants may be inside the mound; the rest are out gathering food. It is best to flood the nests during the day when the observed activity has dropped to a minimum. Flooding is not a sensible option for high-density infestations.

Hope may come in the shape of a fly. In their native South America, parasitic flies affect the Imported Fire Ant. These tiny flies use the ants' as hosts for egg laying and in the process irritate the ants, reducing their ability to forage efficiently. The Texas Fire Ant is also known to be parasitised by two species of phorid flies but unfortunately, these North American flies are not parasites of the Imported Fire Ant. Scientists are working to introduce Pseudacteon flies from Brazil and Argentina that are specific to the Imported Fire Ant species. These small flies are currently the best prospect for biological control of the Imported Fire Ant.