Gamba grass

Native to Africa's tropical and subtropical savannas, Gamba grass is a perennial tussock grass introduced to many parts of the world for use as an improved pasture plant. Gamba grass was imported into Queensland as a pasture grass in 1942, but was not planted on a large scale until about 1983.

Gamba grass is a useful cattle feed in parts of far north Queensland, but also has significant negative impacts, including replacing native plants and increasing fire risk.

Gamba grass is a restricted invasive plant under the Biosecurity Act 2014.

Scientific name

Andropogon gayanus

Description

  • Large perennial grass up to 4m tall with tussocks up to 70cm in diameter.
  • Leaves are 30-60cm long, up to 3cm wide, covered in soft hairs, with distinctive white midrib.
  • Stems are robust, covered in soft hairs.
  • Root system spreads up to 1m from tussock, close to soil surface.
  • Reproduces from seed.
  • Seeds are contained in fluffy V-shaped seed head consisting of up to 6 groups of branches, each containing 2-18 primary branches.

Habitat

  • Almost all known locations are in areas below 980m altitude that receive 400-1500mm annual rainfall.

Distribution in Queensland

  • Naturalised in northern Australia.
  • Currently exists as scattered populations (estimated total of 60,000ha) across Queensland's north, with most sites on Cape York Peninsula and Atherton Tableland.

Life cycle

  • Reproduces by seed and spreads rapidly where natural vegetation has been disturbed.
  • Grows actively in wet season and flowers in April.
  • Seeds develop from May to June and set in July and August.
  • Can produce up to 244,000 seeds/plants each year, with 65% viability.

Affected animals

  • Livestock

Impacts

Environmental

  • Replaces native grasses, reducing natural biodiversity on non-grazed land.
  • High biomass can fuel intense bushfires, leading to loss of tree cover and long-term environmental damage.
  • Recognised (with 4 other tropical grasses) as a Key Threatening Process.

Economic

  • Invades non-grazed parcels of land such as conservation areas, semi-urban residential land and mining leases.

Social

  • High-intensity gamba grass fires can threaten human safety and property.

How it is spread

  • Seeds are light and easily spread by wind, although 90% fall within 5m of parent plant.
  • Also spread by water movement and in mud on vehicles.

Control

Physical control

Hand weeding
  • Hand-pull or dig out isolated plants.
  • Shake excess soil from roots to prevent regrowth.
Fire
  • Tolerates fire at any time of year.
  • Burning gamba grass in dry season can be hazardous to property, people and livestock due to high fuel loads and fire intensity.
  • Low-intensity burns early in wet season can remove old rank growth and promote new growth suitable for herbicide application. These fires can also control young gamba grass seedlings, reducing establishment of new plants.
  • Do not burn gamba grass when plants have mature seeds, as fire updrafts may spread its light, fluffy seeds large distances.
Plant management
  • Graze with enough stock to keep grass below 90cm to limit seed production and potential spread. This prevents plants becoming tall and rank in the dry season and reduces fire hazard. Stocking rates to achieve this may be as high as 5 animals per hectare during peak wet season.
  • Maintain pasture in good condition with high crown and foliage cover to resist gamba grass invasion and spread of existing infestations. Overgrazed or poor pastures are at greater risk of gamba grass invasion due to bare soil and reduced vigour of existing grass species.

Mechanical control

Slashing
  • Slash to reduce seed set or remove old rank growth either before seeding or after seeds have dropped to reduce risk of seed spread. This will also improve herbicide effectiveness and reduce fire hazards.

Herbicide control

  • Spray early in wet season (when leaves are at least 40cm long) or well before May to prevent seeding and potential spread.
  • Spray every part of plant to ensure adequate herbicide uptake. Slash or burn old rank plants to promote fresh growth, enabling more effective herbicide application.
  • Take care to limit overspray, as glyphosate is non-selective and can damage non-target plants.

See the Gamba grass fact sheet (PDF, 811KB) for herbicide control and application rates.

Biological control

  • No known biological control agent.

Legal requirements

  • Gamba grass is a restricted invasive plant under the Biosecurity Act 2014.
  • It must not be given away, sold, or released into the environment without a permit.
  • The Act requires everyone to take all reasonable and practical steps to minimise the risks associated with invasive plants and animals under their 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 and animals in its area. This plan may include actions to be taken on certain species. Some of these actions may be required under local laws. Contact your local government for more information.

More information

Contact us

Call your local government office, or Biosecurity Queensland on 13 25 23.

Last updated
01 July 2016