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Blue mustard (Chorispora tenella)

Blue mustard is an alert weed and a highly competitive agricultural weed in South Australia. It competes with cereal crops and dryland lucerne, and can taint milk if eaten by dairy cattle.

Key facts

Type: Weed, herb.

Native to: Native to Eurasia.

Established in: VIC.

Best time to act: Look for emerging plants during autumn to winter, when blue mustard germinates.

Identification

  • An erect annual herb growing up to 60 cm tall, with branched stems arising from the base.
  • The plant is covered in tiny glandular hairs that are odorous and sticky to the touch.
  • Leaves vary from oval to spear-shaped; larger basal leaves may have toothed or smooth edges and often wither when flowers appear.
  • Flowers have four mauve petals.
  • Long, upward-curving, segmented cylindrical pods hold single round reddish-brown seeds up to 1.5 mm across.

Where it grows

In South Australia it occurs in disturbed places such as roadsides, waste areas and pastures, and tolerates a wide range of moisture, temperature and soil conditions.

Why it matters

  • It is a tenacious, highly competitive agricultural weed.
  • It competes with wheat, other cereals and dryland lucerne.
  • It can taint milk when eaten by dairy cattle.
  • It is difficult to control in grain crops because it is relatively tolerant of the herbicide 2,4-D.

How it spreads

  • Seeds are held in long, segmented pods.

Control options

  • It notes that blue mustard is relatively tolerant of 2,4-D in grain crops.
  • Use registered herbicides or approved methods, following product directions and local advice.
  • Report its presence to PIRSA or a Landscape Board; the National Pest Alert Hotline is 1800 084 881.

Hygiene and washdown

  • Keep vehicles, machinery, livestock and produce moving to or from a property free of weed seeds and plant material.
  • Clean soil and plant material from boots and equipment before leaving an infested site.
  • 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: 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: 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.

  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria

Sources