Mark Newton was at Archerfield Wetlands in Brisbane’s south-west when curiosity got the better of him and he placed his hand beside a red imported fire ant (RIFA) nest. “I wanted to poke the bear,” the retired ecologist says, explaining the stunt he wouldn’t encourage others to try. “I only got about half a dozen ants on me, but that was enough … It was like little sharp pinpoints of pain,” he says. “They just came spilling out of the nest. I could flick those few off but, bloody hell, there were hundreds of them and they were very angry. If they ran all over me, that would be a horrible experience. If [they swarmed] pets or small children, it would be horrible.”
This was Mark’s first – and hopefully last – encounter with the invasive ant species he’d been hearing about since moving to Brisbane in 2022. RIFA first slipped through Australia’s borders sometime before 2001, when infestations were discovered at Brisbane’s port and the south-western Brisbane suburb of Richlands. The Port of Brisbane incursion has been eradicated, along with several other separate infestations in Queensland, New South Wales and Western Australia. Unfortunately, Greater Brisbane’s main RIFA population has proved far more challenging to exterminate and has spread from the south-western suburbs to north of Brisbane, with outbreaks detected across the NSW border in Murwillumbah and Wardell.
Red imported fire ants (Solenopsis invicta) now cover an area spanning 800,000ha, despite $690 million invested in the National Fire Ant Eradication Program (NFAEP), which has been in operation since the pest was first detected. They are contained, but not yet eradicated.
The International Union for Conservation of Nature’s Invasive Species Specialist Group lists RIFA among the world’s worst invasive species. These South American natives have spread to more than 20 countries, moving around the world in shipping containers. They’ve hitchhiked their way in equipment, soil and nursery products across large parts of Mexico, eastern China and the southern United States. These ‘super pests’ are not welcome in Australia.
Huge threat
The threats RIFA pose to Australia are far-reaching and severe. First there are the risks to human health. Mark’s reaction to the few stings he received was mild and short-lived, but many RIFA victims don’t get away so lightly. Pus-filled blisters are common, and the National Allergy Centre of Excellence estimates that one in five sting victims suffer large, extremely itchy welts. As many as two per cent of people stung may develop a life-threatening allergic reaction.
Fire ants thrive in open areas around human settlement and are more active on hot summer days, just when many of us gravitate outdoors. They’re adaptable enough to live across most of Australia. If left to spread, our entire population would be at risk of RIFA stings, resulting in substantial health impacts and healthcare costs. With RIFA at the beach, at the park and in your backyard, the great outdoors wouldn’t be so great any more.
As if risks to our health and backyard barbecues aren’t bad enough, RIFA pose a serious threat to many sectors of Australia’s economy. A 2016 review entitled Red Imported Fire Ant in Australia: What if we lose the war?, in the journal Ecological Management & Restoration, highlighted how much is at stake. If not eradicated, the authors advise, RIFA are likely to impact the agriculture, building and construction, tourism, electrical and communications industries. The 2024 Senate inquiry into RIFA, which was tasked with reviewing control efforts, concluded that a nationwide outbreak could cost Australia up to $2 billion annually.
Agricultural industry leaders are certainly concerned. These digging, chewing, stinging ants munch and tunnel their way through plants, prey on pollinators, injure livestock and impede animals’ access to food and water, AgForce Queensland and Queensland Farmers’ Federation told the inquiry.
Fire ants are already making business difficult for nurseries and garden centres within Brisbane’s fire ant biosecurity zones, where movement restrictions apply for materials that can carry fire ants. “A lot of garden centres are caught up in it,” explains Reece Pianta, advocacy manager of the Invasive Species Council. “Even when they’re not the source of infestations, they’re dragged into the fire ant biosecurity zone with all the regulatory and cost burdens that go with that. We’re talking tens of thousands of dollars-worth of staff time, preventative treatments on the stock they’re selling and the auditing and inspections they’ve got to go through.”
If domestic quarantine arrangements are burdensome, the risks fire ants pose to international trade are even greater. As Reece notes, Australia has a reputation for being a very bio-secure country. “If there’s a risk of someone [getting] fire ants off us in a shipment, then they don’t want the product,” Reece says. “There’s an international reputation at stake here.”
Perhaps most devastating of all is the impact fire ants could have on Australian flora and fauna. RIFA eat just about anything and, as Mark witnessed, they swarm, spilling out of their nest to aggressively defend their colony. This means ground-dwelling and ground-nesting fauna and slow-moving animals are particularly at risk. “They will attack ground-nesting birds and eggs where they can,” Reece says. “They’ll attack stationary animals and fight other insects.” Many ground-nesting birds, including the ground parrot, little tern, plains-wanderer and bush stone-curlew, are already threatened species. It’s likely that fire ants would add another challenge to their dwindling populations.
Based on the experience of countries such as the USA and China, where RIFA have spread extensively, fire ants could wreak all sorts of havoc in Australia, from out-competing native ant communities to eating frogs and attacking hatchling lizards and snakes. Young left unprotected in dens, as baby platypuses are, may also be vulnerable to fire ant attack. As well as injuring and killing individual animals, fire ants can transform entire ecosystems by chomping their way through native plants, disrupting pollination and seed dispersal, and competing for native species’ plant and invertebrate foods.
Because RIFA have so far been controlled in Australia, our ecosystems have not felt the full brunt of their arrival. But, if not eradicated, the Invasive Species Council warns, the damage wrought by RIFA in Australia could surpass that caused by feral cats, wild dogs, foxes, camels, rabbits and cane toads combined.
Is eradication still possible? “Yes,” says Ashley Bacon, executive program director of the NFAEP. But fire ants are a formidable foe. RIFA bear the scientific name Solenopsis invicta. The Latin word ‘invicta’ means ‘unconquered’ or ‘invincible’ – and for good reason. “It’s an invasive species almost perfectly adapted to survive in the Australian environment,” Reece says. “When it floods, fire ants can form huge rafts by locking their legs together. They put the queen and the eggs in the middle and then the raft will slowly rotate so the ants on the bottom are getting a chance to breathe. The whole colony floats on the water and sets up in a new dry location.” And when there’s low rainfall, RIFA go underground, where they can survive in a subsistence state. “They can survive that way for years,” Reece says. “Fire ants are amazing. I don’t want them in this country but as a creature in their natural environment they are just amazing.”
Eradication
No other country has successfully eradicated a RIFA incursion as big as south-east Queensland’s, but NFAEP is giving it a red-hot go. The program is delivered by Biosecurity Queensland and funded by all states, territories and the Commonwealth Government in a cost-sharing arrangement that will take responsibility for a nationwide eradication effort. The Queensland Government’s Fire Ant Suppression Taskforce focuses on helping landowners manage fire ants while awaiting eradication treatment.
Eradication will be achieved by means of NFAEP’s Fire Ant Response Plan 2023–27, dubbed the ‘horseshoe plan’. “First we need to contain the ant,” Ashley Bacon says. “To do that, we’ve created a continuous surveillance area around the infestation in the south-east corner of Queensland and within that a 10km-wide eradication treatment area. In that area, we need to treat 100 per cent of target properties multiple times over several years. Once we’ve completed treatment in one band, we’ll incrementally move the eradication area inward. We respond to detections outside the containment boundary as quickly as possible – we need to get on top of them to ensure we stop the spread.”
Inside the eradication treatment band, in what’s called the suppression area, not everyone is happy with the new approach. Some communities have seen a reduction in fire ant control and feel neglected. “The change in strategy has meant that in some previously treated areas some residents may feel we’ve taken a step back,” Ashley says. “We can’t treat 800,000ha all at once in a synchronised way; we’ve got to delimit the infestation area and then move our way back in.”
This doesn’t mean communities plagued by fire ants can’t control them in the meantime. Local councils, industry and residents can all play a part in knocking down fire ants by treating properties they own or manage. “Local, state and federal government agencies are already on board,” Ashley says. In some local government areas, free fire ant treatment kits are available to residents.
There are three main weapons in the ant-busting arsenal. The first line of treatment for high-risk situations, such as where public safety is at risk, is a liquid contact insecticide injected directly into RIFA nests by a licensed pest manager. “It’s quite slow-acting at the dilution we work with,” says Dr Erin Wallace, a scientist with the NFAEP. “That allows the ants to wander through their nest and come into contact with the insecticide. Their behaviour doesn’t change for a couple of days, so they’re not aware that there’s something toxic in their environment. If we have anything that smells too strongly or acts too quickly there’s a risk of the nest splitting, and the queen not getting the dose that’s needed.” In lower-risk situations, a fast-acting insecticide that acts mostly on foraging worker ants is used.
“We use this if we’re looking for a quick knockdown in an area that’s not high risk because the results can vary depending on the time of year, the temperature, and whether the ants feel like foraging that day. It may not necessarily get through to the queen in the quantities necessary to kill her, because it may take out the workers too quickly.”
The weapon of choice in the eradication treatment area is a granular bait containing an insect growth regulator, the same active ingredients used in pet flea collars. This prevents the fire ant queen from producing healthy reproductive workers. “It’s like the contraceptive pill for ants,” Erin says. “To get rid of a fire ant colony, we need to get the queen.” Depending on the size of the property, handheld spreaders, ‘side-by-side’ vehicles and even small aircraft are used to spread the bait.
Targeting ant biology
While fire ant eradication is feasible with the current tools, Erin hopes that new technologies will simplify and speed up the process. Gene silencing, which prevents the expression of specific genes, is one possibility. “Adult fire ants can’t digest proteins,” Erin says. “If they find a chunky piece of food that’s high in complex proteins, they have to take that to the colony. They give it to a fourth instar [stage] ant larva, placing it on a specialised food basket organ. That larva then digests it into a liquid and the workers consume the liquid,” she explains. “If we can block gut function in the life history stage that digests proteins, that’s going to have a big effect.”
Colony recognition cues are another target for gene silencing. “When ants meet each other, they’ll touch each other with their antenna,” Erin says. “They’re saying, ‘I’m of the same colony, I’m not a danger’.” If pheromones for colony recognition could be turned off, it could cause colony collapse. “It could force workers to turn on their own queen if they don’t recognise her,” Erin says. “We’re targeting very specific parts of the fire ants’ biology with that technology, which would make it very species specific. If we can get that up, that would be a huge win.”
Fire ant eradication is still technically feasible, but it will take a whole-community approach, with locals, industry and all levels of government playing a role for it to be successful, the NFAEP told the Senate inquiry into RIFA. It has been, and continues to be, a massive investment. “But stack that up against the cost of failure,” Reece says. “We need to deal with this, once and for all.”
