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Parodi's spikerush (Eleocharis parodii)

Parodi's spikerush is an introduced aquatic sedge that can form dense stands in Australian wetlands and waterways. These stands can crowd out native wetland plants and interfere with water movement and waterway use.

Key facts

Type: Weed, aquatic.

Native to: South America.

Established in: .

Other names: Parodi's spike-rush, South American spikerush.

Best time to act: Look for it when stems and spikelets are well developed, and treat before seed sets, with follow-up checks during active growth.

Identification

  • It is a perennial, rush-like plant that grows in or beside shallow water.
  • The erect green stems are cylindrical and leafless-looking, with reduced leaves forming sheaths near the base.
  • Plants can grow in clumps from creeping underground rhizomes.
  • A small brown spikelet sits at the tip of each stem.
  • The fruit consists of small nutlets within the spikelets.
  • Look-alike: It resembles native Eleocharis spikerushes; close examination of the spikelets and fruit may be needed for identification.

Where it grows

In Australia it grows in shallow freshwater wetlands, drains, irrigation channels, ponds and the margins of waterways.

Why it matters

  • Dense growth can displace native wetland plants and reduce habitat variety.
  • Thick stands can obstruct drains and interfere with water movement.
  • Infestations can impede access to and use of waterways.

How it spreads

  • It can spread by seed and by creeping underground rhizomes.
  • Water can carry seeds and plant fragments to new sites.
  • Rhizome fragments and seed-bearing material can be moved on machinery, boats, footwear or contaminated soil.

Control options

  • For small patches, carefully dig out plants and rhizomes, taking care not to break them into fragments; collect and dispose of removed material so it cannot return to water or spread.
  • Where chemical treatment is appropriate, use only herbicides registered for the situation and approved for use near or in water, following the product label and local advice.
  • Avoid disturbing infested areas in ways that spread fragments, and check treated sites repeatedly for regrowth and new seedlings.
  • Report suspected new infestations to the relevant state or territory biosecurity agency and follow its guidance.

Hygiene and washdown

  • Clean mud, seeds and plant fragments from boats, machinery, footwear and equipment before leaving an infested waterway, and contain the washings so they cannot reach drains or waterways.
  • Do not move contaminated soil or plant material to clean sites.
  • 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: 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: 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.

Sources