Invasive pasture grasses in northern Australia - Gamba grass

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Gamba grass (Andropogon gayanus)

Gamba grass was first introduced to the Northern Territory in 1931 for testing as a pasture grass. In 1942, it was introduced to Queensland, but large-scale planting only began around 1983. It has naturalised in the east Kimberley region of Western Australia, in the northern parts of the Northern Territory, and in coastal and sub-coastal areas of North Queensland.

Gamba grass under state and territory legislation

Gamba grass is a Weed of National Significance and it is also a declared weed throughout northern Australia.

Under Western Australia’s Biosecurity and Agriculture Management Act 2007, it is a prohibited plant under section 12. It has been placed in the C2 control category. It must be eradicated if it is in low enough numbers or in sufficiently limited areas that eradication is still feasible.

Under the Northern Territory’s Weeds Management Act 2001, further introductions of the species into the Northern Territory are prohibited and populations must be managed according to the declaration zone in which they occur. Areas which have isolated and low density gamba grass populations have been classified as the Class A/C Zone. In these areas the species is to be eradicated in all areas of the Northern Territory except where it is classified as Class B. Widely distributed and dense gamba grass infestations are within the Class B/C Zone. In these areas land managers must control its growth and prevent spread as detailed in the weed management plan for gamba grass.

Under Queensland’s Land Protection (Pest and Stock Route Management) Act 2002, gamba grass is a declared Class 2 pest – land managers must take reasonable steps to keep land free of the species and it is an offence to introduce, keep or supply the species without a permit.

Priority actions/research (recent or underway)

• As a result of the 2013 review of weed management operations for gamba grass in the Northern Territory, the government has increased the eradication zone (Class A/C) to include four large areas of land formerly in the management zone (Class B/C).
• Northern Territory Fire and Rescue Officers are conducting awareness and extension activities by advising land holders of the presence of gamba grass when undertaking ‘permit to burn’ inspections.
• The Northern Territory Government has developed a gamba grass webpage.
• The Northern Territory Government periodically runs the Gamba Grass Assistance Program which includes equipment loans and free herbicide to control gamba grass.
• Kakadu National Park aims to keep free of new infestations of gamba grass and to eradicate some existing limited known infestations.
• Gamba grass was declared a Weed of National Significance (WoNS) in 2012. A WoNS coordinator for gamba grass was funded until the end of June 2013. The coordinator prepared the Weeds of National Significance Gamba Grass (Andropogon gayanus) Strategic Plan 2012–2017.
• Reducing the impact of tropical grassy weeds through effective risk management, S. Setterfield et al. (2011–12), RIRDC National Weeds and Productivity Research Program. This project focused on the Darwin/Daly region of the Northern Territory, which is a nationally significant area with high biodiversity and cultural values. It commenced development of a strategic planning framework to prioritise gamba grass management. This decision-making tool continued to be developed within the National Environmental Research Program (NERP), with application to multiple weeds and additional regions.
• Gamba Grass Effects on Savanna Carbon and Fire, Setterfield S, Hutley L, Rossiter-Rachor N, Douglas M, Adams V, Richards A, National Environmental Research Program (NERP) North Australia Hub. The approach of this project will compare impacts of gamba grass invasion on carbon stocks, fire risk, biodiversity, and other assets, and integrate these results into a decision-support tool to determine the optimal control strategy to maintain savanna carbon stores and other assets.
• Managing flammable high biomass grassy weeds, Setterfield S, Hutley L, Rossiter-Rachor N, Meier S, Douglas M, Bushfires and Natural Hazards CRC (commencing 2015). This project will assess the likelihood and magnitude of risk of high biomass invasive grasses to fire regimes in the tropical savanna region and provide critical information for Government policy and planning, particularly prioritisation of weed risk for fire-regime changing species, and for fire management planning.
• National Environmental Research Program (NERP) researchers continue to work with Northern Territory and Queensland government agencies to improve understanding of the distribution, impacts and management of the five grasses. Current work includes developing decision support tools that better incorporate economic assessments of management costs and modelling the potential future spread of invasive grasses.

Resources