Fine-bristled burr grass (Cenchrus brownii)

Fine-bristled burr grass is a serious grass weed of Australia’s tropical coasts and northern islands.

Profile

How does this weed affect you?

Fine-bristled burr grass has the potential to invade native rangelands and become a troublesome weed of pastures, crops, beaches and coastal areas. The spiny burrs are easily dispersed by stock and native animals. It is closely related to buffel grass, Cenchrus ciliaris, a northern Australia pasture species.

Where is it found?

Native to the Americas, from the USA through to Peru. Distributed throughout Africa, tropical Asia, North America, South America, Australasia and the Pacific.

It is not known how fine-bristled burr grass entered Australia. Currently located in the northern areas of Western Australia, Northern Territory and Queensland. It is also located on many islands off Australia’s north coast.

Currently not known to exist in New South Wales.

How does it spread?

Plants reproduce only by seed. The burrs easily attach to clothing or animals, spreading to new locations. Most dispersal is through human movement of contaminated soil and hay. It is thought that it was introduced into the Torres Strait by contaminated vehicles and earth-moving machinery.

Lifecycle

An annual grass, with a flowering spike (seed head) emerging between April and June.

What does it look like?

Similar in appearance to, and easily confused with, Mossman River grass (Cenchrus echinatus).

Stem

• initially grow horizontal, then upright growing 25–110 cm tall
• sometimes takes root at the nodes

Leaf

• 8–40 cm long and 4–13 mm wide
• hairless
• a fringe of hairs, 0.6–1.3 mm long, occurs at the leaf base

Seed head

• cylindrical, 3–12 cm long and 1.5 cm wide
• green
• contains many burrs crowded together

Burr

• 3.5–4 mm wide
• has an outer ring of barbed spines, up to 7 mm long
• inner area consists of inter-crossing spines of similar length

Seed

• encased and shed within the burr
• egg-shaped
• 1.9–2.6 mm long

What type of environment does it grow in?

Prefers humid tropical and sub-tropical climates. It can grow in a variety of soils and in disturbed areas. It is often found growing close to the ocean and on limestone soils. 

Acknowledgements

Written by Rachele Osmond.

Reviewed by Rod Ensbey.

References

Department of the Environment (2011) Weeds in Australia: Cenchrus brownii, Australian Government. Available atwww.environment.gov.au.Accessed August 2014.

Hosking JR, Sainty GR, Jacobs SWL & Dellow JJ (in prep) The Australian WeedBOOK.

Mullen, CL, Dellow, JJ & McCaffery, AC (2012), Spiny burrgrass PRIMEFACT. Available at http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0006/265056/Spiny-burrgrass-Primefact-web.pdf.   Accessed September 2014

Pacific Island Ecosystems at Risk (PIER) (2008). Cenchrus brownii, Institue of Pacific Islands Forestry, US Forest Servce. Available at http://www.hear.org/pier/species/cenchrus_brownii.htm. Accessed September 2014.

Simon, BK and Alfonso, Y (2011) Grasses of Australia: Cenchrus brownii, AusGrass2. Available at: http://ausgrass2.myspecies.info/content/fact-sheets. Accessed September 2014.

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Control

There are no specific control measures documented for fine-bristled burr grass. Control and management practices used for Mossman River grass, may be used for the control of other noxious Cenchrus species.

Being an annual, the key to control and management is to prevent seeding and reduce the seed bank. Use a combination of control methods and always conduct monitoring and follow-up treatments. Use property hygiene practices to reduce the risk of seed spread. This will give the best chances of success.

Pasture management

Maintain a vigorously growing perennial pasture with little to no bare space. This will provide strong competition against the invasion of fine-bristled burr grass. Avoid heavy grazing on pastures with only small infestations as bare patches of ground provide the opportunity for it to quickly grow and set seed.

Physical control

For individual plants and small infestations, manually remove plants by hand or hoe. Remove as much of the root system as possible. Treat at the seedling stage of growth and before the seed head emerges. Repeat treatments will be required as new seedlings emerge.

Herbicide control

Herbicides registered for use on Cenchrus species should be applied when plants are actively growing and before the seed head emerges. This is usually in summer, but under optimum growing conditions can be year round. Use a foliar spray application.

Herbicide options

See Using herbicides for more information.

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Glyphosate 360 g/L (Various products)
Rate: 2 to 3 L per ha
Comments: Boom spray
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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Glyphosate 360 g/L (Various products)
Rate: 500 to 700 mL per 100 L of water
Comments: Spot spray
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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Glyphosate 360 g/L (Various products)
Rate: 75 to 100 mL per 15 L of water
Comments: Knapsack spray
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
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 pest 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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Reviewed 2018