After 15 years, an invasive weed dubbed a “thorny horror” has been eradicated from Queensland.
Biosecurity officials have declared the eradication of karroo thorn after the trees were detected and destroyed at properties on the Darling Downs in the state’s south.
The African native weed was first detected in Australia in Perth in 1967 and was subsequently planted as an ornamental in zoos and gardens across most states, according to the Department of Agriculture and Fisheries (DAF).
Karroo thorn plants have been found and destroyed on the Darling Downs in Queensland. (Supplied: Biosecurity Queensland)
The tree, which has 10 centimetre long spikes and can overrun landscapes, was first detected in Queensland in 2008 on properties near Millmerran, west of Brisbane.
However, it was only recently declared eradicated from Queensland after officials felt confident no seeds had survived.
Keen-eyed farmer alerts authorities
Johannes Roellgen is one of the landholders who found the weed on his farm and alerted authorities.
He said he was not sure how the plant got to his property, but was happy to see it gone.
Johannes Roellgen has worked with authorities to eradicate karroo thorn on his farm. (ABC Rural: Brandon Lon)
“They came out multiple times to keep on checking and poisoning any new shoots and new plants, and we’re very pleased to know that it now has been eradicated,” Mr Roellgen said.
“It really all comes down to good communication and collaboration between landowners and the department to try and get on top of those nasty pests.”
Biosecurity officer Ted Vinson said the eradication was a significant achievement.
“It’s a never-ending fight, but it is nice to get on top of something,” Mr Vinson said.
He said the plant was “very invasive”, taking over grasslands and making them unproductive for livestock and dangerous for bushwalkers.
“They really can mark the landscape quite dramatically,” he said.
The DAF said the weed could have become a bigger problem than prickly acacia, which is one of Queensland’s worst weeds, costing up to $30 million in lost grazing production and controls each year.
‘We should be grateful’
Dr Carol Booth is a senior policy analyst at not-for-profit biosecurity organisation Invasive Species Council.
She said Queenslanders should be grateful that future generations had been saved from this “thorny horror”.
“It mightn’t seem such a big deal to eradicate a plant — after all, plants can’t run away and hide,” Dr Booth said.
“It typically needs many years, often decades, of persistence to exhaust the seedbank in the soil and to find every plant.”
Victoria eradicated the weeds from known sites in 2018, and according to the West Australian government, there is no known plants in the state.
One plant, found near Bega, New South Wales, is being closely managed, the government says.
The battle continues
Weeds cost agricultural producers $4.3 billion nationally and $549 million in Queensland every year, according to a 2023 research report by the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES).
Mr Vinson said of particular concern were cactus species that were “starting to get away”, so councils and the state government were taking steps to control them and speak to landholders.
Andreas Glanznig says there’s need for a national plan to develop weed biocontrol agents. (Supplied: CISS)
Andreas Glanznig, chief executive at government-funded biosecurity agency Centre for Invasive Species Solutions, said there was a pressing need for governments, industry and research agencies to work together.
“A collaborative approach is really going to enable us to put in place a national plan to look at how we develop that next set of weed biocontrol agents,” Mr Glanznig said.
