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Mossman River grass (Cenchrus echinatus)

Mossman River Grass is a serious weed of maize, sugarcane, cotton, peanuts and pastures, and sometimes affects orchards, vineyards and vegetable and soybean crops. Its rapid growth competes for light, moisture and nutrients, while its spiny burrs can injure people and animals, slow harvesting and contaminate sheep’s wool.

Key facts

Type: Weed, grass.

Native to: Central America and southern North America.

Established in: QLD, NSW, SA, WA, NT.

Other names: Mossman Burr Grass, Southern Sandbur, Field Sandbur, Sandbur.

Best time to act: Look for rapid growth after germination in the hot, humid period of late spring and early summer, and treat before burrs form on flowering stems, which develop between January and May.

Identification

  • It is an upright, loosely tufted, short-lived annual grass, usually 25–60 cm tall and occasionally reaching 100 cm.
  • Its leaf blades are 5–25 cm long and 3–12 mm wide, often with hairs along the margins; the sheaths may have a reddish or purplish tinge.
  • The spike-like flower head is 3–10 cm long and bears 5–50 stalkless, burr-like structures, each 4–10 mm across.
  • The burrs have sharp, rigid spines 2–5 mm long and hairy bristles; they are reddish or purplish-green when young and straw-coloured or dark brown when mature.
  • Brown, egg-shaped seeds are 1.5–3 mm long and 1.3–2.2 mm wide, and are enclosed within the burrs.
  • Look-alike: It resembles Buffel Grass (Cenchrus ciliaris) and Spiny Burrgrasses (Cenchrus spinifex and Cenchrus longispinus), but Mossman River Grass has stalkless burrs with one row of larger flattened spines.
  • Look-alike: Cenchrus spinifex has almost stalkless burrs with several rows of larger flattened spines, while Cenchrus longispinus has shortly stalked burrs with several rows; Buffel Grass does not produce spiny burrs.

Where it grows

In Australia it occurs across all states and territories except Tasmania, in places including disturbed sites, roadsides, parks, waterways, wetlands, pastures and crops, with largest populations in northern Western Australia and coastal Queensland.

Why it matters

  • It is a serious weed of maize, sugarcane, cotton, peanuts and pastures, and sometimes orchards, vineyards and vegetable and soybean crops.
  • Its quick growth makes it a vigorous competitor for light, moisture and nutrients.
  • Spiny burrs can injure and inconvenience people in crops and slow harvesting, increasing costs.
  • Burrs may contaminate sheep’s wool and reduce its value, and can injure stock, horses and dogs.

How it spreads

  • It reproduces by seed, mostly spread when the spiny burrs attach to animals, vehicles and clothing.
  • Burrs may also be dispersed by water and in contaminated agricultural produce.

Control options

  • Control is most successful when seed production is prevented, before burrs appear.
  • Plants can be hand pulled, burnt or controlled by cultivating the soil.
  • Repeated treatments are needed to control new seedlings as they emerge, and dense pasture cover limits establishment.
  • For chemical options, check current registered herbicides and Australian Pesticides and Veterinary Medicines Authority information.

Hygiene and washdown

  • Clean machinery and vehicles to help prevent burrs spreading.
  • 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): No national listing. Managed under state and territory law.
  • 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: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Declared weed, Class B. Class B: growth and spread must be controlled. All declared weeds are also Class C, so they must not be brought into the NT.
  • 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.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development
  • Northern Territory: Territory Parks and Wildlife Conservation Act 1976 (NT), administered by NT Department of Lands, Planning and Environment

Sources