The green tree ant is known for its colourful body and sharp bite, but Queensland fruit growers are also using it as a creative method of organic pest control.
Far North Queensland durian grower Andrew Kang has actively used green ants for five years to get rid of sap-sucking and fruit-spotting bugs, and even larger animals like sulphur-crested cockatoos.
"If there are enough [ants] on the fruit it will actually deter the cockatoos from the fruit itself," he said.
"It's probably more suitable for a natural sort of farming like permaculture.
"Some trees have super strong colonies [of ants], and every fruit will be protected, whereas I would notice there'd be weaker colonies and maybe they protect 60-70 per cent of the fruit on that tree.
Mr Kang does not spray his orchard but said he would sometimes use a drone to help move the birds.
To create a pest-management system he moves groups of green ants from an existing colony to new trees and gives them food to get started.
"As you can imagine green tree ants aren't very friendly, so it involved a lot of running across the paddock from tree to tree," he said.
"It wouldn't be a 100 per cent success rate but possibly 70 per cent of them would stay."
Innisfail farm manager Gavin Eilers said he had also noticed green ants warding off pests from his tropical fruits like rambutans and mangosteens.
"Green ants play a vital role in our orchards," he said, "just keeping some of the pests and diseases at bay naturally, rather than spraying with herbicides and pesticides.
"Most definitely, where there's green ants the fruit's a hell of a lot cleaner [of bugs]."
How it works
Charles Darwin University professor Alan Andersen is known as Australia's Ant Man.
The terrestrial invertebrates expert said green ants could protect crops because they were extremely hostile to other creatures.
"It's not just eating them, but it's scaring them off because they're so aggressive," Dr Anderson said.
"Any creature that comes and annoys the ants, it will sort of elicit this aggressive formic acid squirting and biting behaviour, and so they'll just leave.
"They can defend the plant against insects that would otherwise harm the plant, but of course a lot of insects are beneficial to plants and particularly pollinators.
"There have been quite a few studies on this … the positive impact of warding off the enemies outweighs the negative impact on reducing pollinators."
The ants also weave a silk web around fruit on trees – trapping scale bugs.
However, Mr Kang said this left dark residue on the fruit and leaves.
"As far as the quality of the taste, I have not noticed any difference whatsoever," he said.
"I just tell [customers] that that's my little trademark."
Charles Darwin University's Keith Christian also said despite black marks on the fruit, there was no rotting or significant damage, only slightly higher sugar content.
Research shows farm success
Dr Christian and colleague Renkang Peng researched agricultural applications for green ants for several years across northern Australia and south-east Asian countries like Thailand.
Dr Christian said everywhere they researched they found that green ants were very effective at keeping pests away from tree crops, and were more economically efficient and more effective than chemical sprays.
"Really any tree crop, there is potential for them," he said.
"One of the big advantages is that they're always on the job.
"Whereas when farmers usually detect a pest on their crop, it's usually too late … the pests have done some damage.
"I would recommend it for any farmer in the north, or any horticultural crop like mangoes, cashews, tropical citrus."
He said despite his and Dr Peng's research, 10 years on there had been very little uptake by Australian farmers.
"There is a non-standard farming practice, I guess, involved," he said.
"I think if there were more extension officers … out there assisting the farmer with that from government agencies, then to overcome those hurdles then I think it would become more common.
"There are lots of advantages, very few disadvantages and so I would strongly recommend it."
