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Noogoora burr (Xanthium occidentale)

Noogoora burr is widespread across most of New South Wales and can compete with summer crops and pastures, reducing yields and contaminating grain. Its burrs can injure people and livestock, devalue wool, and help the plant spread; seedlings are poisonous to livestock.

Key facts

Type: Weed, herb.

Native to: Southern United States, Mexico and the West Indies.

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

Best time to act: Look for seedlings from late winter to summer and treat plants while young and actively growing, before they set seed.

Identification

  • A stout, erect annual plant that grows mainly in summer and can reach 2 m high.
  • Plants may have a single stem or many branches; stems are hairy and mottled purple and green.
  • The alternate leaves are rough, broad ovate to triangular, and cut into 3 to 5 lobes, with darker green upper surfaces and purplish veins.
  • The hard, woody burr is 16 to 22 mm long and more or less egg-shaped, turning brown when mature.
  • Burrs are densely covered with hooked spines 1 to 3 cm long and have straight, almost parallel terminal spines, or beaks, 3 to 5 mm long.
  • Look-alike: Burr shape and size are the main way to distinguish Xanthium burr species; Noogoora burr has hard, woody, egg-shaped burrs 16 to 22 mm long with long hooked spines and straight, almost parallel beaks.

Where it grows

In New South Wales it occurs across most areas except the southern tablelands, commonly in riparian areas, roadsides, wasteland, pastures and cultivated low-lying or periodically flooded areas.

Why it matters

  • It competes with summer crops such as cotton, corn and soybeans, reducing yields and contaminating grain, and it competes with pastures.
  • Burrs can injure people and livestock and devalue wool.
  • The plant is poisonous to livestock, especially as seedlings, which are more likely to be eaten than larger plants.
  • Dense infestations can form barriers for people and livestock and limit access to watercourses.

How it spreads

  • The plant reproduces by seed contained in burrs, which usually disperse in autumn and winter but can remain attached to undisturbed plants until spring.
  • Burrs spread by sticking to animal wool and fur, floating in waterways, and through movement of contaminated grain, gravel and machinery.
  • Seeds germinate in moist soil from late winter to summer; flushes can follow summer storms, irrigation or floods.

Control options

  • Preventing seed set is the most important part of management; repeated control may be needed because germination can occur in multiple flushes from late winter to summer.
  • Control young seedlings with cultivation, including inter-row cultivation in crops; large populations can also be treated by slashing or registered herbicides.
  • Use spot spraying, chipping or hand-hoeing to follow up smaller or scattered populations and prevent seed set; monitor treated sites for further germination.
  • Maintain pasture ground cover and avoid overgrazing in spring and summer; take care that livestock do not graze toxic seedlings.

Hygiene and washdown

  • Remove burrs from slashing or mowing equipment to prevent spread.
  • Burrs can be carried on animal wool and fur and moved in contaminated grain, gravel or machinery, so check these pathways when working in infested areas.
  • 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: Regionally prohibited / regionally controlled / restricted weed (varies by region). Where it is regionally prohibited, landowners must take all reasonable steps to eradicate it on their land. Where it is regionally controlled, landowners must take all reasonable steps to prevent its growth and spread on their land. Where it is a restricted weed, trade in it (including the plant, its seed or contaminated material) is prohibited.
  • South Australia: Declared plant. Depending on the declaration, it can be an offence to move it on public roads or sell it, and landowners may be required to control it on their land.
  • Western Australia: Not listed. Not found in the Western Australian Organism List. Check with DPIRD before moving or keeping it.
  • Tasmania: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • 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: Declared pest. It is a declared pest throughout the ACT.

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
  • Australian Capital Territory: Biosecurity Act 2023 (ACT), administered by ACT Biosecurity
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • 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