Giant rat's tail grass

Native to Africa, giant rat's tail grass is a long, upright grass that forms large tussocks. Like other weedy Sporobolus grasses, it is an aggressive grass that can reduce pasture productivity and significantly degrade natural areas.

Giant rat's tail grass was introduced to Australia around the early 1960s in contaminated pasture seed. Giant rat's tail grass is now found from northern Cape York in Queensland to the New South Wales central coast. Ecoclimatic modelling suggests giant rat's tail grass is suited to conditions present in 30% of Australia (223 million hectares).

You must manage the impacts of giant rat's tail grass on your land.

You must not give away, sell or release giant rat's tail grass into the environment.

Scientific name

Sporobolus pyramidalis, S. natalensis

Description

  • Upright grass 0.6-2m tall.
  • Long, narrow leaf blades 20-50cm long, 2-4mm wide.
  • Seed head is up to 45cm long, 3cm wide.
  • Seed heads generally change shape from 'rat's tail' spike when young to elongated pyramid shape when mature although this may vary.
  • Difficult to distinguish from other pasture grasses and native Sporobolus grasses before maturity.
  • Unlike giant Parramatta grass, giant rat's tail grass does not develop sooty spike on its seed heads.

Habitat

  • Suits wide range of soils and conditions.
  • Ecoclimatic modelling suggests giant rat's tail grass is suited to conditions present in 60% of Queensland (108 million hectares), including areas receiving as little as 500mm average annual rainfall.

Distribution

  • S. natalensis and S. pyramidalis is found from northern Cape York to New South Wales border.

Life cycle

  • Can produce up to 85,000 seeds per square metre in a year, with initial seed viability of about 90%.
  • Significant portion of seed can remain viable for up to 10 years.

Affected animals

  • Livestock and native fauna

Impacts

Economic

  • Quickly dominates pastures, particularly after overgrazing or soil disturbance.
  • Causes losses in livestock carrying capacity and decreases production by up to 80%.
  • Can increase teeth wear of cattle and horses that graze on it.

Environmental

  • Degrades conservation and natural areas, reducing ecosystem values and habitat for native fauna.

How it is spread

  • Seeds spread by livestock in manure and on fur and hooves.
  • Also spread by feral and native animals, vehicles and machinery (especially slashers and earthmoving equipment), in hay and untested pasture seed, and by fast-flowing water over turf.

Control

  • A combined approach of different control methods, including herbicides and mechanical, with land management practices that maintain soil cover is most effective.
  • For small isolated infestations:
    • hand-chip, bag and remove tufts then burn them
    • spot spray with glyphosate and/or flupropanate
    • manage competitive pasture species to maintain as much soil vegetative cover as possible, fertilise where appropriate.
  • For larger scattered infestations:
    • spot spray with glyphosate and/or flupropanate
    • manage competitive pasture species to maintain as much soil vegetative cover as possible, fertilise where appropriate
    • consider establishing a vigorous pasture to strongly compete against established giant rats tail grass plants and to suppress Sporobolus re-establishment.
  • For larger dense infestations:
    • apply glyphosate through a pressurised wick wiper where appropriate
    • boom spray or jet spray with glyphosate and/or flupropanate as per label or permit directions
    • manage competitive pasture species to maintain as much soil vegetative cover as possible, fertilise where appropriate
    • consider establishing a vigorous pasture to strongly compete against established giant rats tail grass plants and to suppress Sporobolus re-establishment
    • where appropriate burn prior to cultivating to reduce viable seed bank
    • spot spray or hand-chip fence lines, headlands, drainage lines, shelter belts and any surviving or newly established weedy Sporobolus grasses to prevent reseeding.

See the rat's tail grasses fact sheet (PDF, 2.4MB) for herbicide control and application rates.

Biological control

  • The Queensland Department of Agriculture and Fisheries (DAF) is working with the New South Wales Department of Primary Industries to assess the effectiveness of  endemic fungal pathogens for giant rat’s tail grass control.
  • DAF is assessing potential biological control agents from Africa for giant rat’s tail grass control.

Legal requirements

  • Giant, American and giant Parramatta rat’s tail grasses are category 3 restricted invasive plants under the Biosecurity Act 2014.
  • Other restricted rat’s tail grasses are giant Parramatta grass (S. fertilis) and American rat’s tail grass (S. jacquemontii). These species are widespread but less common in Queensland than giant rat’s tail grass. You must  must not  give away, sell, or release into the environment. Penalties may apply.
  • You must take all reasonable and practical measures to minimise the biosecurity risks associated with dealing with Giant, American and giant Parramatta and rat’s tail grasses under your control. This is called a general biosecurity obligation (GBO).
  • At a local level, each local government must have a biosecurity plan that covers invasive plants in its area. This plan may include actions to be taken on giant American and giant Parramatta rat’s tail grasses.. Some of these actions may be required under local laws. Contact your local government for more information.

Further information