Improving gamba grass control on Cape York Peninsula

Gamba grass was planted across northern Australia as a pasture species in the mid-1980s and has spread rapidly. In north Queensland, gamba infestations are found near Bamaga, Coen, Weipa, Cooktown and Mareeba. The grass is also widespread along Cape York roadsides and in isolated patches in the Gulf region. Despite being declared as a Weed of National Significance in 2012, and listed as a key threatening process under the Environmental Protection and Biodiversity Conservation Act, it continues to spread, increasing fire risks and significantly disrupting biodiversity and ecosystem services. Environmental, social and economic costs will increase unless control is improved.

The lack of herbicides registered for use in natural areas is a major barrier to managing gamba grass and other high biomass grassy weed species in the north, especially where infestations cover large areas. Few selective herbicides are available with on-label registration for use in these non-crop areas and therefore current control relies heavily on ‘minor use’ permits. Non-selective herbicides such as glyphosate have off-target effects on native vegetation so are inappropriate for use in natural areas at large scales.

This project is reviewing herbicide and integrated management approaches to controlling gamba and trial various control methods in natural ecosystems to inform best practice and herbicide registration processes. The trials are assessing off-target herbicide effects and recovery following treatment and biomass removal. The project is developing best-practice management guidelines to control gamba incursions and infestations in natural areas, including control methods for selective herbicide application. The guidelines are assisting land managers to better manage gamba, and project outcomes are relevant to the entire gamba grass range across the NT, WA and Qld.

This project is:

  • consolidating knowledge about the distribution and spread of gamba grass in north Queensland, the effectiveness of controlling gamba in natural areas, and how gamba biology affects control success
  • testing gamba control methods in the field
  • providing practical best-practice solutions for controlling gamba incursions in natural areas
  • providing guidelines to scale up control methods to manage larger gamba infestations
  • informing the management of other high biomass grassy weeds across northern Australia to reduce their environmental, social and economic costs
  • addressing priorities in the EPBC’s Threat Abatement Plan for high biomass grassy weeds and inform savanna carbon accounting.

Project activities

  • Consolidate knowledge, identify research gaps and plan field trials through desktop research and collaborative workshops
  • Run field trials to test the efficacy of several herbicides and application methods to control gamba grass outlier incursions and core infestations in natural areas
  • Collect and collate data about the distribution and potential spread of gamba grass in north Queensland to inform containment and buffer management strategies
  • Develop best-practice management guidelines for gamba grass incursions and infestations based on trial results.

Anticipated outputs

  • A review of the effectiveness of current management approaches for gamba grass
  • Guidelines on best-practice management of small outlier gamba grass incursions, new occurrences and large gamba grass infestations
  • Scientific papers and datasets
  • Communication products such as factsheets and summary recommendations.

This project is led by Dr Helen Murphy from CSIRO, with field monitoring by CSIRO’s Matt Bradford and Andrew Ford. Dr Murphy is being assisted by Queensland Government staff as well as researchers from Charles Darwin University and The University of Western Australia.

This project is due for completion in June 2021.

Helen Murphy, CSIRO
E: [email protected]

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  • Management options for high biomass grassy weeds are currently limited. Photo: Glenn Campbell.
  • A gamba grass tussock. Photo NESP NAERH.
  • Person in front of a late wet season tall stand of gamba. Photo NESP Northern Hub.
  • Gamba grass dominating the ground level of an ecosystem. Photo: Michael Lawrence-Taylor.
  • Gamba grass invading the understory. Photo: Sam Setterfield.
  • Assessing the impact of gamba grass. Photo: NESP NAERH
  • Gamba grass tussocks. Photo: NESP NAERH.