Tropical fire ants (Solenopsis geminata) are an unwelcome guest in many areas of the Northern Territory. They arrived in Darwin about 80 years ago and settled in happily, also hitching a ride to other major settlements in the north.
Closely related to red fire ants, which are a significant problem in Queensland, tropical fire ants (also known as ginger ants) have a vicious sting, which produces the burning sensation that gives them their name, and can result in red itchy lumps lasting several days. It can also cause anaphylactic shock in people allergic to wasps, ants or bees.
That, however, is only one reason they’re unwelcome. Like everything else, they have to eat. And while they’ll eat just about anything, they have a particular fondness for sap and honeydew, and have a mutually beneficial relationship with some sap-sucking insects. They protect the sap-producing insects from parasites and predators, and also eliminate diseased or unhealthy individuals, allowing the insects to grow and flourish. This can aggravate the problem caused by the insects in the first place, and reduce plant productivity. It can also lead to outbreaks of disease and further attack from pests.
Tropical fire ants also readily sting people tending or harvesting crops.
Getting rid of them is difficult, but it can be done. Some of the world’s largest pest ant eradications have occurred on the Tiwi Islands, north of Darwin.
On Melville Island, two of the areas where tropical fire ant infestations have been wiped out are the second and fourth largest ant eradications in the world - 252 and 59 hectares respectively.
This is such a remarkable achievement that Tiwi Tropical Fire Ant Project won the Biodiversity category of the 2015 United Nations Association of Australia World Environment Day Awards, were in Melbourne on June 5.
Since 2003, CSIRO has been working with the Tiwi Land Rangers and the Tiwi Plantations Corporation to eradicate tropical fire ants from Melville Island, the second largest island in Australia.
Tiwi Land Ranger supervisor and mentor, Willie Rioli said the ants probably got to the Tiwi Islands in barge cargo from Darwin.
“We now have introduced biosecurity protocols and monitoring that will help prevent pest ants arriving on the Tiwis in the future”, he said.
“But we need to make sure the ants don’t leave Darwin in the first place - that’s why quarantine is so important.”
CSIRO’s Dr Ben Hoffmann said it took a few years to get the protocols right but, once that happened, eradication took less than two years in the places the work focused on.
“However, the work is very labour intensive. Each individual nest must be located and treated”, he said. “It’s much like looking for needles in a haystack, but on a very large scale.”
Mr Rioli said the control of Tropical fire ants could not have been achieved without the strong support of the Tiwi people.
“The work involved fifty three inspections over ten years of every household at Pirlangimpi on Melville Island”, he said. “The residents of Pirlangimpi have been fantastic – we couldn’t have done it without them.”
The eradication efforts on Melville Island haven’t stopped yet. Two infestations are still in progress: one at Yapilika, the other at Milikapiti.
Dr Hoffmann said winning the UNAA award was great recognition for all of the hard work that has gone into the project but that ongoing funding was crucial to the success of future eradications.
“We’ve already demonstrated how we can successfully eradicate highly invasive ant species on the Tiwi Islands. We just need extra support to finish the job off,” he said.