The venomous fire ants Cyclone Alfred is sending our way
By Mike Foley
Venomous fire ants swept up in floodwaters from Cyclone Alfred are forming teeming rafts and travelling downstream, sparking fears that the invasive pest will infest new areas such as NSW and further afield.
A video shot this week shows thousands of fire ants clinging together and floating in streams in Queensland’s Scenic Rim region, near the Gold Coast.
“Disturbingly, new footage shows this rafting behaviour happening right now in flood-affected areas with high fire-ant density,” the Invasive Species Council’s Reece Pianta said.
Fire ants have infested greater Brisbane, where an eradication effort is under way. While all the rivers in the region flow eastwards to sea, not into NSW, there are concerns that flooding will drive interstate spread of the invasive pest.
High density infestations have sprung up at many locations, such as outer Brisbane and the Gold Coast, increasing the likelihood of the ants being accidentally transported across state borders in “carrier materials” – such as landscape supplies.
“I have seen more videos of fire ants rafting in Ipswich, Gold Coast and Logan areas, showing this is an increasing phenomenon that reflects the increasing density of the fire-ant population,” Pianta said.
“A property owner may think they are fire ant free, but they could well have an infestation after these floods, and ants are into their turf, mulch, soil or hay that are inadvertently moved over the border into NSW.”
Fire ants are a growing problem in the Brisbane electorate of Logan, represented by Treasurer Jim Chalmers, as well as Opposition Leader Peter Dutton’s electorate of Dickson.
Fire ants mound in a horse paddock in Waterford, south of Brisbane, in October 2024.Credit: Dan Peled
Last year, more than 100 nests of fire ants were discovered on an army base west of Toowoomba.
A jointly funded eradication program in Queensland will cost $592 million over the four years to 2027. Former inspector-general of biosecurity Helen Scott-Orr told a Senate inquiry last year that double that amount, up to $300 million a year, was needed until 2032 to achieve eradication.
Fire ants first arrived in Australia at Brisbane in 2001 via international shipping. The outbreak from that incursion is ongoing, with a National Fire Ant Eradication Program treating 8000 square kilometres around Brisbane and the Gold Coast to remove the pest.
Fire ants have been detected in Melbourne and Hobart in the past year, and twice in NSW.
They entered the US from South America in the 1930s. Eradication efforts failed and fire ants have colonised about 20 per cent of the US.
In most cases, fire ant bites cause a burning sensation that lasts about an hour and can create blisters and pustules.
The National Allergy Centre of Excellence, Australia’s peak allergy research body, estimates fire ants sting a third of people who live in areas where they have established colonies each year.
It said if a nationwide infestation were to occur, up to 650,000 people would seek medical attention for bites every year, including up to 175,000 people for allergic reactions such as hives, welts and swelling that in severe cases could be fatal.
The Australasian Society of Clinical Immunology and Allergy has said fire ants were three times more likely than bees to cause anaphylaxis – a life-threatening allergic reaction. In 2021, there were 927 hospital visits due to bee stings and 12 deaths from anaphylaxis from bee and wasp stings.