Mexican feather grass (Nassella tenuissima)

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How does this weed affect you?

Mexican feather grass, is a potentially serious weed of pastures, native grasslands and woodlands. It is a highly adaptable grass that has the potential to infest up to 65% of New South Wales (NSW), causing major economic and environmental damage.

Mexican feather grass is unpalatable to stock, difficult to control and capable of growing in a variety of climates and soil types. It is able to tolerate prolonged periods of drought and can flourish in areas that are heavily grazed.

Mexican feather grass is closely related to serrated tussock (Nassella trichotoma), an invasive weed of temperate grasslands, and can only be distinguished when in flower. Mexican feather grass was initially found in some NSW nurseries, mislabelled and marketed as ‘elegant spear grass’, a name given to the native grass Austrostipa elegantissima.

During 2008, a wholesale nursery based in Victoria imported seed of ornamental stipoid grasses. It is believed that the seed was either mislabelled or contaminated with Mexican feather grass seed, which was then propagated, sold and distributed. The plants may have been sold under the names of Stipa lessingiana, S. capillata, S. capriccio or Stipa Regal Sensation.

Online overseas seed companies have also marketed the plant under various names including Stipa tenuissima, Stipa tenaccissima, elegant spear grass, white tussock, Texas tussock grass and ponytail grass.

How does it spread?

Mexican feather grass reproduces by seed. From mid spring to summer it germinates freely on well-drained soils where there is little competition from other vegetation. Seeds can be dispersed by becoming attached to clothing, livestock and vehicles, or from contaminated seed and fodder.

What does it look like?

Mexican feather grass is a dense, upright tussock up to 70 cm.

Leaves are 0.25–0.5 mm wide, up to 60 cm long and tightly rolled with overlapped edges. Leaves roll smoothly between the fingers like a needle, but feel coarse when sliding fingers downwards along the leaf blade. The ligule (a small, thin structure at the base of the leaf blade) is 0.5–2.5 mm long, opaque, papery and smooth.

Flowering stems are up to 70 cm high, round, smooth and hairless, with 2–3 unthickened nodes.
The flower head is 15–25 cm long and green or purplish in colour. An identifying feature of the plant is that the flower head does not detach from the plant and it has a leaf-like sheath that encloses its lower section.

Seeds are 2–3 mm long and encased by two purple or reddish-brown glumes, 6–10 mm long. Another distinguishing feature is the awn, which is 4.5–9 cm long and attached centrally to the end of the seed.

Acknowledgements

Written by Alan Maguire; prepared by Annette M^cCaffery and Annie Johnson; 2013 edition reviewed by Michael Michelmore; edited by Elissa van Oosterhout.

References

• Csurhes S (2008) Mexican feather grass (Nassella tenuissima)—Pest plant risk assessment, Queensland Department of Primary Industries and Fisheries, Brisbane
• Maguire A (2005) Mexican feather grass. NSW DPI Agfact P7.6.60
• Victorian Department of Primary Industries (2004) Landcare Notes – Mexican feather grass: State prohibited weed, Frankston.

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Control

You must report this plant if you see it anywhere in NSW. Call the helpline listed above. Help will then be provided to remove and destroy it. This serious weed could spread if control efforts do not follow all protocols. Not reporting it is a breach of your legal biosecurity duty.

Herbicide options

See Using herbicides for more information.

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PERMIT 9792 Expires 30/11/2020
Flupropanate 745 g/L (Tussock®)
Rate: 1.5 to 3 L per ha
Comments: Broadacre control
Withholding period: Don't graze cows or goats that are being milked on treated areas. Blanket sprayed pastures - grazing or cutting for stock feed - 120 days. Spot sprayed areas - grazing or cutting for stock feed - 14 days. Don't graze stock on treated areas for 14 days prior to slaughter.
Herbicide group: J, Inhibitors of fat synthesis (Not ACCase inhibitors)
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2020
Flupropanate 745 g/L (Tussock®)
Rate: 100 to 300 mL per 100 L of water
Comments: Spot spray control
Withholding period: Don't graze cows or goats that are being milked on treated areas. Blanket sprayed pastures - grazing or cutting for stock feed - 120 days. Spot sprayed areas - grazing or cutting for stock feed - 14 days. Don't graze stock on treated areas for 14 days prior to slaughter.
Herbicide group: J, Inhibitors of fat synthesis (Not ACCase inhibitors)
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2020
Flupropanate 745 g/L (Tussock®)
Rate: 500 mL per 10 L water
Comments: Wiper suppression
Withholding period: Don't graze cows or goats that are being milked on treated areas. Blanket sprayed pastures - grazing or cutting for stock feed - 120 days. Spot sprayed areas - grazing or cutting for stock feed - 14 days. Don't graze stock on treated areas for 14 days prior to slaughter.
Herbicide group: J, Inhibitors of fat synthesis (Not ACCase inhibitors)
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2020
Glyphosate 360 g/L (Roundup®)
Rate: 3 L per ha
Comments: Broadacre control
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2020
Glyphosate 360 g/L (Roundup®)
Rate: 1 L 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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PERMIT 9792 Expires 30/11/2020
Glyphosate 360 g/L (Roundup®)
Rate: 3.3 L per 10 L water
Comments: Wiper suppression
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 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.
All of NSW	Prohibited Matter A person who deals with prohibited matter or a carrier of prohibited matter is guilty of an offence. A person who becomes aware of or suspects the presence of prohibited matter must immediately notify the Department of Primary Industries

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Reviewed 2018