Farmers in New South Wales have raised concerns as a severely invasive weed show signs of resistance towards a key herbicide, in a nationwide first.

Key points:

  • The country’s first instance of herbicide resistance in African lovegrass has been detected
  • Only two chemicals are currently used to prevent the weed’s spread in Australia
  • Landholders are encouraged to monitor their paddocks and participate in the expanding survey of the weeds

South East Local Land Services investigated 12 populations of African lovegrass from the New South Wales Snowy Monaro region, with results showing five samples tested had become resistant to the herbicide Flupropanate.

Andrew Rolf owns land in central Monaro and said it was scary to see the first signs of herbicide resistance.

“It means that one of our tools, which was very useful in controlling African lovegrass, may now be off the table.”

A woman stands in a field of brown weeds.

Jo Powells from the South East Local Land Services surveying the spread of African Lovegrass in the Monaro region.(

Supplied: South East Local Land Services

)

A ‘prolific’ weed

The lovegrass was first accidentally introduced into Australia from South Africa before the 1900s and has drastically spread in recent years.

Only two chemicals are currently approved for use against the weed, including glyphosate and flupropanate, which these latest survey results show is now failing.

Another invasive perennial weed causing concern in New South Wales is the serrated tussock, which also showed signs of resistance to flupropanate during surveys in 2017.

For Mr Rolf, both weeds can wreak havoc on their land.

“Serrated tussock is definitely up there, but lovegrass has just been such a prolific weed,” Mr Rolf said.

grassy weeds in a field

Serrated tussock, another troubling perrenial grass weed, has also shown signs of herbicide resistance.(

Supplied: South East Local Land Services

)

Landholders advised to monitor paddocks

While the populations in the Monaro region are the first to show signs of resistance, there are concerns that it could happen in other populations susceptible to a significant use of the herbicide.

Senior Agricultural Advisor with South East Local Land Services, Jo Powells, said while the findings are disappointing, they were not surprising.

“It is concerning that we have identified five populations at this point which are showing resistance to flupropanate,” Ms Powells said.

“It’s not overly surprising given the long-term usage of this herbicide.”

Potted weeds in green potts against a wall.

South East Local Land Services collected seed samples from the Monaro and sent them across to Adelaide to Plant Science Consulting for testing.(

Supplied: South East Local Land Services

)

Warning against reliance on one control technique

Landholders who struggled with the spread of the lovegrass have been urged to monitor their paddocks closely and diversify their control methods.

Ms Powells said one of the major problems landholders faced in mitigating the spread was their limited options.

“There’s not a huge range of options and we have only two key chemical options for control,” Ms Powells said.

“But grazing management, soil fertility management and pasture improvements are all other options to consider.”

The Local Land Services says a limited number of fully subsidised herbicide resistance tests will be available for land managers to participate in the expanded survey.

Blow for farmers as ‘prolific’ weed develops resistance to herbicide in Australian first
Source:
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