Mesquite in retreat at Mary K

Mesquite control a rare success story in NW weed eradication

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One of Southern Gulf NRM's photo monitoring points showing the extent of the mesquite killed around the Mary Kathleen mine site. Pictures supplied.

One of Southern Gulf NRM's photo monitoring points showing the extent of the mesquite killed around the Mary Kathleen mine site. Pictures supplied.

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While weed control in semi-arid and tropical parts of Queensland has generally been a story of chasing an uncaged beast, Southern Gulf NRM and the state's Department of Agriculture have each been able to report success with capturing a number of species before they fully escaped.

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While weed control in semi-arid and tropical parts of Queensland has generally been a story of chasing an uncaged beast, Southern Gulf NRM and the state's Department of Agriculture have each been able to report success with capturing a number of species before they fully escaped.

In the first instance, the joint federal-state Disaster Recovery Funding Arrangements Weeds and Pest Management Program has been credited with the eradication of more than 95 per cent of mesquite weed species located along watercourses at the Mary Kathleen uranium mine site.

In the second, the Queensland Weedspotters' Network, co-funded by Biosecurity Queensland, the Queensland Herbarium and local governments, have been able to cut six high-risk invasive plant species - grey willow, white willow, yellow fever tree, grey-haired acacia, thorn tree Acacia nigrescens and cactus Opuntia santarita - off at the pass.

Mesquite was planted over the top of tailings dam rehabilitation work following the closure of the Mary Kathleen uranium mine in 1984, presumably for soil stabilisation purposes.

Mesquite was originally planted to stabilise the Mary Kathleen uranium mine tailings dam rehabilitation work.

Mesquite was originally planted to stabilise the Mary Kathleen uranium mine tailings dam rehabilitation work.

According to Southern Gulf NRM project officer Charles Curry, the extreme climate conditions of prolonged drought and then 2019's major flooding event created ideal conditions for it to flourish.

"During the 2019 monsoon floods, every creek and river in the vicinity of the Mary Kathleen tailings dam flooded," he said. "The dense stands of mesquite on the tailings dam and scattered around and downstream were expected to unleash a mass of regrowth down the Cameron River."

To treat the impending disaster, Southern Gulf NRM engaged a local contractor with a team of 10 to basal bark spray mature and regrowth mesquite down creeks from the Mary Kathleen plant.

"This rather arduous project was conducted professionally and a kill rate well in excess of 95 per cent has been achieved with no damage to native vegetation or to the multitudes of small fish observed in the waterholes of Cameron River," Mr Curry said.

"Follow-up activities by the Mount Isa Landcare Group some months later treated surviving mature mesquite and all regrowth mesquite on part of the tailings dam and along the creeks flowing into Cameron River as well as several kilometres down Cameron River; a highly successful operation."

Mr Curry said while that had been a success story, they would have to contend with regrowth for a number of years yet.

He added that a core infestation in the McKinlay region had been successfully treated but a number of others around Hughenden, Burketown, Kynuna and Cloncurry were the subject of ongoing work and funding applications.

"Mesquite is just one weed species targeted in the program to assist producers with weed and pest management on their properties," he said.

Early detection key to nipping six species in the bud

Meanwhile, Biosecurity Queensland's general manager for invasive plants and animals, Dr John Robertson said the six plant species nipped in the bud were major pests overseas and had been targeted for early detection and removal in Queensland since the mid-1990s.

"It's is a great outcome that helps protect millions of hectares of grazing land from potentially invasive plants," he said.

All six high-risk weed species were detected in, or near gardens, before they had a chance to spread.

A Biosecurity Queensland officer removing the cactus Opuntia from a suburban garden. Picture - Biosecurity Queensland.

A Biosecurity Queensland officer removing the cactus Opuntia from a suburban garden. Picture - Biosecurity Queensland.

"Most of Queensland's worst weeds, including prickly pear cactus and lantana, are escaped garden plants," Mr Robertson said. "Early detection and eradication of high-risk weed species is vital."

Weedspotters now has an 1800-strong army of trained volunteers searching for potentially invasive plants, using a mix of traditional and innovative surveillance techniques to help detect weeds much earlier than previously.

According to Mr Robertson, 27 plant species have been eradicated from Queensland altogether, thanks to partnerships with local governments and other agencies.

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