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Uruguayan rice grass (Piptochaetium montevidense)

Uruguayan rice grass has been recorded at only one location in Australia and has not been found in NSW, but it could compete with native plants if it establishes. Its dense tussocks, resistance to grazing and stimulation by fire make new outbreaks important to detect and report promptly.

Key facts

Type: Weed, grass.

Native to: Argentina, Bolivia, southern Brazil, Paraguay, Uruguay and Chile; also considered native in parts of North America..

Established in: .

Best time to act: Inspect and report suspect tussocks promptly, preferably before seeds can be dispersed.

Identification

  • A perennial grass forming dense tussocks to about 0.5 m high.
  • Its narrow leaf blades are about 0.5 mm in diameter, hairless and covered with minute rough projections; the jointed stems are almost the same length as the leaves.
  • The hairless ligule is 1–2 mm long, and the leaf sheath may have scattered hairs.
  • Dense, branched flowering heads grow to about 100 × 15 mm.
  • Seeds are about 2 mm long with a curved, bristle-like awn about 10 mm long; young glumes are purplish and up to 3.5 mm long.
  • Look-alike: It is related to Nassella species, including serrated tussock and Chilean needle grass, so expert identification is advisable when a similar tussock-forming grass is suspected.

Where it grows

It grows best in temperate and subhumid climates, often in disturbed, degraded, relatively fertile soils used for grazing or farming, although it can also invade less-disturbed vegetation; the only Australian record was near Altona, Victoria.

Why it matters

  • Dense tussocks may compete well against native plants.
  • The plant is resistant to grazing and is stimulated by fire.
  • It produces many seeds in South America, and an Australian outbreak could spread and become harder to eradicate if control is poorly carried out or not followed up.

How it spreads

  • Seeds are dispersed by wind and can be spread when browsing animals eat the plant and later excrete viable seed.
  • Movement of contaminated soil can spread seed.
  • Anecdotal evidence suggests stock do not carry or disperse the seeds externally.

Control options

  • Report suspected plants or new outbreaks promptly to the local council weeds officer and the state herbarium, and seek expert identification and control advice.
  • Do not attempt control without expert assistance; poorly performed control can help spread the weed.
  • Where experts advise, use an authorised method, including physical removal or a herbicide only where its current label or permit allows use for the situation, and follow all label directions.
  • Revisit treated sites and follow up as advised to check for surviving plants or new outbreaks.

Hygiene and washdown

  • Clean soil and plant material from vehicles, machinery, boots and equipment before leaving infested or suspect sites, and avoid moving potentially contaminated soil.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): National Environmental Alert List. One of 28 weeds named on the National Environmental Alert List as early-stage invaders with serious potential to harm the environment.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Check NT list. There is no NT weed profile for it. Check the NT declared weeds list for its current status.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

Sources