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Low-volume high-concentration applications of glyphosate to control gamba grass (Andropogon gayanus)

Setter, M. J., Setter, S. D., Perkins, M. L., McMillan, H. and Campbell, S. D. (2022) Low-volume high-concentration applications of glyphosate to control gamba grass (Andropogon gayanus). In: 22nd Australasian Weeds Conference, 25 – 29 September 2022, Adelaide, South Australia.


Publisher URL: https://researchoutput.csu.edu.au/ws/portalfiles/portal/262619333/22AWC_Proceedings_Rev_B_SEC_IDX.pdf


Gamba grass (Andropogon gayanus Kunth.) is a tussock-forming perennial species capable of out-competing other pasture grasses to form dense stands up to 4 m tall. Infestations occur in the Northern Territory, Queensland, and Western Australia, but its current distribution is only a small proportion of its potential range. Once established, gamba grass impacts on the biodiversity and ecosystem function of an area, whilst also imposing a significant fire hazard due to the large biomass that it produces. Controlling invasive grasses amongst other desirable grass species is a challenge, particularly in difficult to access areas where movement of vehicles and equipment is impaired.

To overcome some of these challenges, we undertook a rate response trial on gamba grass to test the efficacy of low-volume high-concentration applications of glyphosate. At a field site near Mt Garnet in North Queensland, a dense stand of gamba grass was slashed in December 2017 and allowed to regrow until April 2018. A randomised complete block experiment comprising seven treatments, three replicates and clusters of 15 gamba grass plants as experimental units was then established. Using a gas operated splatter gun attached to backpack style equipment, six rates of glyphosate (0, 9, 18, 27, 36, 45 and 54 g a.i. L-1) were applied, with each plant directly receiving 4 mL of herbicide mixture per half metre of plant height. An untreated control was also included for comparison. After 3 months, gamba grass showed a strong dose-dependent response ranging from 30% mortality at 9 g a.i. L-1 to 100% mortality at rates of 36 g a.i. L-1 or higher. Regrowth of any surviving plants was also adversely affected at rates above 9 g a.i. L-1 with plants taking longer to reshoot. While promising, a follow up trial has been undertaken on more mature gamba grass plants to determine if similar results can be achieved.

Item Type:Conference or Workshop Item (Paper)
Business groups:Biosecurity Queensland
Keywords:Herbicide, invasive grasses, splatter gun, weed control.
Subjects:Science > Invasive Species > Plants > Biological control
Science > Invasive Species > Plants > Effect of herbicides
Science > Invasive Species > Plants > Weed ecology
Plant pests and diseases > Weeds, parasitic plants etc
Plant pests and diseases > Pest control and treatment of diseases. Plant protection > Organic plant protection. Biological control
Agriculture > By region or country > Australia
Agriculture > By region or country > Australia > Queensland
Live Archive:18 Jan 2023 02:51
Last Modified:06 Feb 2024 04:44

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