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Whorled pigeon grass (Setaria verticillata)

This introduced annual grass is a weed of crops and disturbed ground, and is listed as invasive in Australia. Its fast growth and sticky, barbed seed heads help it spread and can make it troublesome in crops and during harvesting.

Key facts

Type: Weed, grass.

Native to: Old World, with its native range uncertain and possibly including Europe and Africa..

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

Other names: Bristly foxtail, Rough bristle grass, Bur bristle grass, Barbed bristle grass.

Best time to act: Look for plants as they grow and treat them before the sticky seed heads mature and release or attach to anything.

Identification

  • A loosely tufted annual grass that can grow up to 1 m tall, with spreading stems that may root at lower nodes.
  • Leaves are soft and usually hairless, up to 30 cm long and 1–1.5 cm wide.
  • The narrow, cylindrical, spike-like flower head is about 5–15 cm long, with spikelets clustered around the central stem.
  • Each spikelet has one to three bristles with backward-pointing barbs, making the seed head cling to fur, clothing and other vegetation.
  • Look-alike: Green foxtail (Setaria viridis) and yellow foxtail (Setaria pumila) are similar weedy grasses, but typical S. verticillata has backward-barbed bristles that make its flower heads sticky.

Where it grows

It grows in disturbed ground, including crops, roadsides and waste places, and can occur across a wide range of climates and soil types.

Why it matters

  • It competes with a wide range of crops and can become abundant in crop fields.
  • Its tangled flower heads can interfere with harvesting by catching on themselves and the crop.
  • It can become dominant in grassland and displace native grasses.
  • It can host some crop nematodes and plant viruses.

How it spreads

  • The backward-pointing bristles catch on animal fur, clothing, footwear and other inflorescences, moving seeds to new sites.
  • Livestock movement and traded wool can carry attached seeds, while contaminated crop seed or crop products can move them farther afield.
  • The whole seed head may also be carried on animal fur or hairy insects.

Control options

  • For small infestations, remove plants before seed heads mature, and contain and dispose of seed-bearing material so it cannot spread.
  • Conventional tillage can control this annual grass where cultivation is suitable; use registered herbicides only where permitted for the site or crop, and follow the product label.
  • Check treated areas for new seedlings and follow up before they set seed, as seeds can persist in soil for several years.
  • Contact the relevant state or territory biosecurity agency for local advice and to check whether reporting is required.

Hygiene and washdown

  • Clean clothing, boots, equipment and vehicles after working in an infestation, removing and containing any clinging seed heads.
  • Avoid moving contaminated soil, crop material or fodder to clean 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: 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: 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.

  • 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
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • 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