Biosecurity Spotters logo

Manchurian rice grass (Zizania latifolia)

Manchurian rice grass is listed on Australia's National Priority List of Exotic Environmental Pests, Weeds and Diseases as a significant environmental and social amenity risk. It can form persistent, dense stands that displace wetland plants and interfere with water flow and access to waterways.

Key facts

Type: Weed, aquatic.

Native to: Eastern Asia, including China, eastern Siberia and the Russian Far East.

Established in: .

Other names: Manchurian wild rice, Water bamboo.

Best time to act: Survey during active growth, when the tall shoots and branched flower heads are visible, and treat promptly before plant material or rhizome fragments are moved.

Identification

  • A perennial, rhizome-forming wetland grass, usually 1–2.5 m tall and sometimes reaching 4 m.
  • Its broad, linear leaves are about 50–90 cm long and 1.5–3.5 cm wide.
  • The erect stems can root at their lower nodes, and underground and surface rhizomes produce multiple shoots.
  • Branched flower heads are about 30–50 cm long, with male spikelets on lower branches and female spikelets on upper branches.
  • The female spikelets have long awns, while the smaller male spikelets have shorter awns.
  • Look-alike: It may be confused with other tall wetland grasses, including common reed (Phragmites australis); its broad leaves and large, branched flower head are useful identification features.
  • Look-alike: Misidentification among Zizania species is possible.

Where it grows

In Australia, it would suit waterlogged wetlands, shallow lake and river margins, estuaries, drainage ditches and other wet sites.

Why it matters

  • Dense stands can outcompete and displace other wetland plants, changing the structure and composition of plant communities.
  • Stands can block drains and water channels, impede water flow and increase the chance of flooding.
  • Extensive growth can cover open water and interfere with access and activities such as fishing.
  • It can invade damp pasture and cropping areas, affecting land use.

How it spreads

  • Plants for planting are a major pathway for movement; the species has been used as an ornamental and for habitat planting.
  • Rhizomes produce new shoots, and small rhizome fragments can grow into new plants and spread to new sites.
  • Seeds may also spread, though seed production can be limited or absent in introduced populations.

Control options

  • Get identification and control advice from the relevant state or territory biosecurity agency, and report suspected plants where required.
  • For small infestations, remove the whole plant and rhizomes where practical, collect every fragment and dispose of plant material through an approved method.
  • Mechanical excavation can remove plants from ditches and banks, but avoid moving rhizome fragments to clean sites.
  • If chemical control is appropriate, use only herbicides registered for the site and aquatic setting, follow the label and local approvals, and return to check for regrowth.

Hygiene and washdown

  • Before leaving an infested site, clean mud and plant fragments from boots, tools, vehicles, machinery and boats, and contain and dispose of the debris appropriately.
  • Do not transfer water, soil or plant material from an infested waterway to another 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): National priority exotic pest. On the National Priority List of Exotic Environmental Pests, Weeds and Diseases, so any new detection should be reported straight away.
  • 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: Declared pest (C1), prohibited. C1 Exclusion: to be kept out of WA, or out of the parts of WA where it is not established. Report any sighting to DPIRD. It must not be brought into WA (prohibited organism).
  • 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.

Sources