Two of the worst ant pests on the planet are invading Australia. Red imported fire ants have been detected for the first time on the western side of the Great Dividing Range in Toowoomba, Queensland. Yellow crazy ants recently reached the Whitsundays.
The yellow crazy ant (Anoplolepis gracilipes) ranks among the world's 100 worst animal pests because of its impacts on agriculture and biodiversity. The red imported fire ant (Solenopsis invicta) poses similar threats, and is also one of the world's most dangerous ants. Its intensely painful stings, which give the ant its name, can kill people.
The red imported fire ant is one of the world's most dangerous ants. Dept of Primary Industries/AAP
The prospects of total eradication of these ants in Australia are poor. Both species are highly adaptable and colonies need to be detected and eradicated early to contain them. Eradication efforts face other several challenges, including:
- inadequate biosecurity resources for checking incoming cargo
- the need for the public to maintain constant vigilance
- spread from built-up urban areas into bushland that's much harder to monitor
- other pressing issues, such as the housing crisis, demand attention and resources, crowding out threats from insects.
Where did the crazy ants come from?
The origin of yellow crazy ants is disputed but is likely in South-East Asia or Africa. Workers are yellowish orange, medium-sized (around 4-5mm) and have long legs and antennae. They run rapidly in a seemingly random fashion, hence their name.
Workers and queens have a small funnel on their gasters (the bulbous end of their bodies) from which they can spray formic acid. It can burn human skin and is lethal for other ants and many native arthropods. Small animals such as lizards and bird chicks are at risk of being blinded or eaten.
These ants have spread to much of South-East Asia, parts of central America and the United States. They can be found indoors in the United Kingdom and a handful of European nations.
Since reaching the Australian territory of Christmas Island, yellow crazy ants have devastated the native wildlife. They killed up to 20 million of the famous red land crabs, causing major changes in the rainforest.
On the mainland, this species has reached the Northern Territory and Queensland, where it is most entrenched, having been discovered in Cairns in 2001. As well as spreading to Hervey Bay, Townsville and other coastal sites, the ant is now in Brisbane.
Brisbane City launched an eradication plan in 2022. Control measures include baiting using a fishmeal-based ant attractant combined with an insecticide. However, recently reported infestations in the Whitsundays and elsewhere suggest eradication will be difficult.
Northern Territory authorities have had more success. Some 26 locations covering nearly 300 hectares of Indigenous land have been freed of the pest.
The prospects of total eradication of yellow crazy ants in Australia are not promising. Like other serious ant pests, this species can form "super-colonies" with multiple queens, eats a wide variety of foods and readily colonises both exotic and native environments.
Such species are often only eradicated if their presence is detected before they become established. For eradication programs to succeed, local councils need landholders' full support, plus adequate federal and state funding. Late last year the federal government provided another A$24.8 million, so there is some hope.
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Gabrielle Stacey
Landcare Australia
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