UQ researchers drill down on mimosa bush

Brandon Long
By Brandon Long
Updated December 2 2021 - 5:38am, first published December 1 2021 - 10:00pm
DRILLING WEEDS: UQ School of Agriculture and Food Sciences PhD candidate Amelia Limbongan has been tackling the mimosa bush with a drill and herbicide-filled capsules. Photo: UQ.

Queensland researchers say they have found a novel way to kill a little-known weed that is safer, cleaner, easier and as effective as herbicide sprays.

A team from the University of Queensland have been drilling capsules of various dry herbicides into the stems of mimosa bush (vachellia farnesiana), an invasive woody weed which can be a big nuisance during mustering and can also hinder stock access to water.

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The capsule is then sealed into the stem with a wooden plug, the herbicide is dissolved by plant sap and the weed dies from the inside.

Conventionally, foliar, basal bark and cut stump applications using a limited range of herbicides are recommended for control of mimosa bush.

UQ School of Agriculture and Food Sciences PhD candidate Amelia Limbongan said the capsule method used 30 per cent less herbicide to kill weeds and was just as effective as more labour-intensive approaches.

"[This] will save valuable time and money for farmers and foresters ... while also protecting workers by practically eliminating their exposure to harmful herbicides," Ms Limbongan said.

UQ Professor Victor Galea said the system also protected non-target plants, often damaged through traditional spraying.

Mimosa bush can hamper mustering and prevent stock from accessing water. Photo: DAF

Mimosa bush is not a prohibited or restricted invasive plant in Queensland, but it can spread readily and grow quickly.

Despite the impacts of mimosa bush in the Australian context, there is limited published information on control options for the problematic weed, according to the researchers.

In Australia, only clopyralid is currently registered under a minor use permit for foliar applications. A major benefit is the speed of application, but the researchers say it has potential for spray drift and off-target damage.

The cut stump treatment is also an effective option for many woody weeds including mimosa bush and uses similar herbicides to those for basal bark applications. It has the advantage of being effective all year round but is time consuming and laborious.

Basal bark spraying has proven effective for many woody weeds in Australia.

The UQ team conducted the trials near Moree in NSW using a number of different herbicides.

They found injecting aminopyralid and metsulfuron-methyl was consistently most effective on cut stump and intact plants, while clopyralid provided highest mortality when applied to cut stumps and single-stemmed intact plants.

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Ms Limbongan said they had already seen several professional operators and councils adopting the approach and there was a great market for the technology globally.

One of the products tested in the research paper, a glyphosate capsule, is already being sold in Australia along with the applicator equipment.

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Researchers are continuing to trial the capsule method on several different weed species and have a number of similar products in line for distribution.

Three more products are being prepared for registration, with the range set to expand over time.

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Brandon Long

Brandon Long

Queensland Country Life journalist

Brandon Long is a Queensland Country Life journalist based in Toowoomba.

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