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Camel thorn (Alhagi maurorum)

Camel thorn outcompetes pastures and invades crops in parts of Australia. Its sharp spines can injure people, stock and wildlife, and its roots can damage roads by growing through bitumen.

Key facts

Type: Weed, shrub.

Native to: Europe and Asia.

Established in: NSW, VIC, SA, WA.

Best time to act: Look for and treat actively growing plants in spring and early summer.

Identification

  • This perennial shrub grows up to 1.5 m tall and has stiff, branching stems with sharp, yellow-tipped spines 1–4 cm long.
  • Its fleshy, oval leaves are usually at the base of spines, yellow-green on top and blue-green and hairy underneath.
  • Pinkish purple to red and yellow, pea-like flowers grow in clusters of 1–8 and appear in summer.
  • Its smooth red-brown pods are 8–30 mm long, constricted between seeds and usually have a small beak at the end.
  • The plant has deep roots attached to horizontal rhizomes that can extend up to 8 m from the main stem, and it readily suckers.

Where it grows

In NSW it has been found in the Riverina, Murray and Western regions, growing in pastures, along river banks and drainage lines, and in irrigated and disturbed areas.

Why it matters

  • It outcompetes pastures and invades crops, although cattle, horses and sheep sometimes eat it.
  • Its sharp spines can injure stock, wildlife and people.
  • Its roots can grow and sprout through bitumen, damaging roads.

How it spreads

  • Seeds and pods spread by wind, water and livestock, which can eat the pods and pass seeds in their manure.
  • Seeds can remain viable in soil for at least 3 years, and germination is more likely after seeds pass through livestock.
  • New plants can grow from rhizomes and broken root fragments; fragments can spread through livestock, contaminated fodder and machinery, especially cultivation machinery.

Control options

  • Combine control methods and repeat treatments in spring and early summer while plants are actively growing, continuing over several years to exhaust the root system.
  • Hand-pull or dig out seedlings when soil is moist, remove as much root as possible and check for regrowth.
  • Avoid slashing, mowing, mulching and cultivation, as plants can regrow or sucker when cut or when roots and surrounding soil are disturbed.

Hygiene and washdown

  • Avoid moving soil, vehicles or machinery contaminated with camel thorn roots or seeds.
  • Contaminated fodder can spread root fragments.
  • 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: Regional priority in 1 of 11 regions. Regional priority weed in North West. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: State prohibited weed. State prohibited weeds are the highest priority: the Victorian Government is responsible for eradicating them, so report any sighting to Agriculture Victoria.
  • South Australia: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Declared pest (C3). C3 Management: landholders must manage it to reduce its impact and stop it spreading.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • 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.

  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • 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

Sources