The tiny aliens were first spotted in February 2001 in the Port of Brisbane, but it’s suspected they may have been hiding out for years after making the long journey from their native South America, likely hitching a ride aboard shipping containers.
In the two decades since, south-east Queensland has waged war with the highly invasive species of fire ants, initiating a national eradication program that has so far cost the country $690 million, with a Senate inquiry calling in April this year for better cooperation and transparency to ensure its success.
Fire ants, or Solenopsis invicta, are notorious for their painful and burning stings. Two to six millimetres long with copper brown bodies and a darker abdomen, large amounts of their venom could kill humans, pets, livestock, and wipe out native species of animals, according to Professor Nigel Andrew, an entomologist with Southern Cross University.
Andrew expects that if and when they arrive in Victoria, detection of the invasive species is likely to come when sting victims start turning up in hospitals.
According to the National Allergy Centre of Excellence’s narrative review and submission to the fire ant senate inquiry, most victims experience pustules measuring 1-2 mm each forming at the sting site.
Small pustules form on a victim’s arm after fire ant stings. Photo: Invasive Species Council/Murray S. Blum, The University of Georgia via Forestry Images[/caption]
In less common cases, 20 per cent of victims experience a large local reaction where a red, itchy and raised welt appears on the sting site. Though even rarer, up to two per cent of victims allergic to the sting experience life-threatening anaphylactic shocks, requiring medical treatment.
Fire ants have copper brown bodies, ranging from two to six millimetres. Photo: National Fire Ants Eradication Program[/caption]
“Fire ants are on another level,” says Andrew. “If one of them stings you, the whole nest – hundreds and thousands of them – come out. They give off chemicals or pheromones that bring out these masses,” he says.
“They’re very aggressive. Because even though as an individual they’re quite small, as a group, they work as a superorganism.”
Fire ants disrupt the environmental landscape, Andrew says. They compete with rare and endangered native ant populations and feed on seedlings which affect the type of plant species that grow in an area, upsetting the flow of existing ecosystems.
The pests’ incursions have so far mostly been contained to south-east Queensland and northern NSW, thanks to the Queensland government’s Fire Ant Suppression Taskforce (FAST) and enforcement of two main biosecurity zones to restrict “human-assisted movement” of fire ants in carrier materials such as soil, hay, mulch, manure and potted plants.
One biosecurity zone covers the regional areas surrounding outer Brisbane, including the Lockyer Valley, that have undergone or are undergoing eradication treatment. The second zone covers Greater Brisbane, which has yet to receive treatment.
The eradication program administers two treatment methods. The first method is a granular treatment which encourages foraging ants to bring soybean oil-soaked corn grit pieces infused with either an insect growth regulator or a fast-acting insecticide back to their nests. As the active ingredient spreads through the colony, it kills the queen, worker ants and larvae.
In more urgent incursions where there is a risk to public safety and health, a direct nest injection method using insecticide fipronil is added to water that floods tunnels and nests.
“As fire ants are cleared from areas, treatment will progressively move inwards until all areas are free of fire ants,” a National Fire Ant Eradication program spokesperson says.
“Our program oversees efforts to eradicate fire ants from Australia.”
Read more about how fire ants build rafts
But fire ant outbreaks outside these containment zones are increasing despite suppression efforts. Experts are concerned the pest may march both further north and south.
Fully formed fire ant nests are likely to appear dome-shaped, while immature nests could appear as flat, disturbed patches of grass. Photo: National Fire Ants Eradication Program[/caption]
In April, nests were found at the Oakey army base in Queensland in the Condamine-Balonne river system, a major catchment feeding into the Murray-Darling Basin, stirring fears they could be carried on flood waters south to Victoria and South Australia. In late May, fire ants reached Nirimba on Queensland’s Sunshine Coast.
Victorian entomologist Gordon Ley is concerned they could reach the Darling River through the tributaries of the Northern Basin..
“They are threats to most things and animals in Australia,” says Ley, president of the Entomological Society of Victoria.
“They could have more impacts than other invasive species like rabbits and deer, and … cause great potential disasters.”
Andrew agrees and says while the ants could easily arrive in Victoria at any time through the movement of carrier materials across interstate borders, the Murray-Darling river complex offers another transportation mode, making the scale of their expansion “a lot harder to control”.
Experts say there is still hope the pests can be contained if new fire ant colonies are identified quickly, so they can be eradicated.
An analysis conducted by the Australia Institute estimates that fire ants will cost the country more than $22 billion by the 2040s, and that money spent fighting them brings a public benefit of between $3 and $9 for every dollar spent across a 20-year timeframe.
It argues the fire ant eradication plan is underfunded due to methodological flaws in Biosecurity Queensland’s cost-benefit analysis commissioned in 2021, which the Australia Institute says “downplays the economic case for urgent action”.
The current fire ant response plan uses a horseshoe strategy that wraps around known ant-infested areas. Photo: National Fire Ant Eradication Program[/caption]
Last year, the fire ant eradication program devised a new strategy, involving a ten-kilometre wide containment area in South East Queensland which would be blanketed with eradication treatments three times a year.
But this amounted to a reduction of the scale of the eradication effort, according to Invasive Species Council advocacy manager Jack Gough.
Increases in the fire ants’ density, population and the possibilities of human-assisted transport over the next few years are likely to lead to breaches of containment zones, which “completely undermines the strategy”, Gough argues.
“Australia has not seen what a serious fire ant infestation looks like yet. It’s been this sort of west to east strategy, where we go and get rid of those fire ants wherever we can. It’s kept the numbers suppressed,” he says.
“Now, they’re moving to the horseshoe, [but] they haven’t funded the suppression inside that level.”
Gough and Andrew say prioritising suppression means the will and funding for the ants’ elimination is missing.
“It’d be great if the suppression zone was changed into an eradication zone, but then that would mean that the funding would have to be doubled,” Andrew says.
The management of fire ants should be removed from the Department of Agriculture to Treasury, he argues, “because this is a financially massive issue”.
Fire ants merge their bodies together to form a raft to float in water bodies. Photo: Invasive Species Council[/caption]
In Victoria, Agriculture Victoria inspects shipments of host materials from Queensland and enforces trade and market access conditions.
Last December, the Allan government contributed $69.7 million to the cost-shared national program, in addition to its $47.9 million contribution since 2017.
