Soldier thistle (Picnomon acarna)

Soldier thistle is a prickly, upright plant usually growing to 50-75 cm tall. It is a weed in cropping and grazing land and it can injure people and animals.

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How does this weed affect you?

Soldier thistle competes with cereal crops and interferes with harvesting by clogging machinery. Its sharp spines can injure sheep, dogs and humans and decrease suitable grazing areas for stock.

Soldier thistle is a weed of roadsides, waste areas, channel banks, crops and pastures in temperate and occasionally also semi-arid environments.

It can be controlled by hand grubbing, cultivating, mowing, slashing or treating with herbicides before the flowering head develops.

What does it look like?

Soldier thistle is a prickly, upright, annual thistle usually growing to 50-75 cm tall but occasionally reaching 100 cm.  It forms a basal rosette (cluster) of leaves during the early stages of growth. The rosette leaves are slightly lobed, with distinct short yellow spines, and grow to 30 cm long. The stems and leaves are densely covered in white hairs that give them a cobwebby or woolly appearance. The flower heads are cylindrical with pink or purple florets and spiny bracts. The seeds are attached to a pappus made up of many feathery, silver-white bristles up to 2 cm long. 

Where is it found?

Soldier thistle is not present in NSW.

There are infestations in Victoria and South Australia. It is native to southern Europe and south-western Asia

What type of Environment does it grow in?

Soldier thistle grows in semi-arid and temperate regions with 300 - 600 mm rain/year. It tolerates sandy and stony soils. In other states it has formed dense infestations on heavy red-brown soils.

How does it spread?

Seeds are mainly spread by the wind. They may also be spread by water, in animal fur or wool, and in mud stuck to vehicles or machinery.

References

Parsons, W.T., & Cuthbertson, E. G. (2001). Noxious weeds of Australia. CSIRO publishing.

More information

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Control

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.


Glyphosate 360 g/L (Various products)
Rate: 10 mL per 1 L water
Comments: Spot spray. For general weed control in domestic areas (home gardens), commercial, industrial and public service areas, agricultural buildings and other farm situations.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


MCPA 340 g/L + Dicamba 80 g/L (Kamba® M)
Rate: 350 mL per 100L of water
Comments: For thistle seedlings. A repeat spray may be necessary.
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


MCPA 340 g/L + Dicamba 80 g/L (Kamba® M)
Rate: 80 mL per 15 L of water
Comments: For thistle seedlings. Spot spray from a knapsack. A repeat application may be necessary.
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.

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For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW DPI Biosecurity Helpline on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2021