Control Methods
| The best way to manage Gamba grass is to prevent its introduction in the first place. You can prevent the introduction of Gamba onto your block by ensuring that your machinery is free of Gamba seeds, and only allowing clean machinery to work on your land. You can also prevent Gamba introduction by requesting weed free hay, or requesting a vendor declaration for clean hay. It is also important to learn to identify Gamba grass, both when it is young and mature, so you can spray Gamba grass that is around fence lines, before it establishes on your block |  |
Gamba grass is considered relatively easy to kill, and follow up control is generally not required for longer than 3 years, assuming that seed is not re-introduced. Where there are only a small number of plants present, Gamba grass tussocks can be dug up with a mattock. Alternately, chemical control may be used for larger infestations.
Physical
Small infestations or isolated Gamba plants can be removed by hand pulling or grubbing out with a mattock or hoe. It is best to hand pull Gamba grass after rain when the soil is moist. An advantage of manual control is that it minimises soil disturbance, and therefore further Gamba seed germination. In the wet season it is very important that any Gamba plants that are pulled out are not left in contact with the soil, as they will easily re-root (even after the dirt has been shaken off the plant).
Mechanical
Slashing or mowing Gamba grass before it sets seed will reduce seed production and dry matter but will not kill the roots of the grass tussocks, which sprout again the following wet season. However, care must be taken that Gamba grass is slashed before it sets seed in April/May, as slashing after this time only encourages the spread of Gamba, each plant producing up to 250,000 seeds. Regular slashing will encourage smaller, early seeding native grass species.
Chemical
Gamba grass is commonly controlled by chemical means using the herbicide glyphosate. This method is particularly good for large infestations, as a significant number of plants can be killed with a relatively small amount of herbicide and it is relatively cheap. However, care must be taken as glyphosate is a non-selective herbicide that will also kill susceptible native vegetation. Also, infestations around water should be sprayed with products that are safer to use around water e.g Roundup Bioactive™.
For herbicide application to be successful you must make sure that the plants are actively growing and that the entire plant is covered with herbicide. If necessary a dye can be used in the spray so you can identify when herbicide has been applied to the entire plant. To reduce the amount of herbicide that you need you can spray at the beginning of the wet season, when the plants are actively re-sprouting but are still fairly small, or you can burn or slash the Gamba grass, and then spray the resprouting grass. For detailed information about using glyphosate on Gamba grass (e.g dilution rates, coverage, cost etc..) see the Gamba management guide. (add link)
It is necessary to revisit the treated area (after) 3-5 times throughout the growing season to re-spray any areas missed or any new plants. Follow up for another 2 years, checking for any new plants, is essential otherwise the original control is potentially a wasted effort.
Land Management strategies
Burning is a good way of reducing the dead Gamba grass, and if done in the wet season can assist in the regeneration of native vegetation. Wet season burning can be done at any time later in the wet season when the grass is a dry enough to burn. Burning doesn’t kill the Gamba roots, so following up spraying of re-growth is essential.
Minimising soil disturbance also helps limit the further spread of Gamba, as it grows well in disturbed areas, such as cleared areas and along tracks. Where soil disturbance does occur, such as due to grading, there has to be follow up spraying the first wet season afterwards. When grading avoid creating wind-rows as these create a perfect seedbed for gamba and other weeds.
Grazing by cattle and buffalo is sometimes the only answer to control large gamba infestations. This method is being used throughout Coomalie on roadsides and vacant lands, where the cattle do a great job eating out Gamba. Like any control method it has to be done with knowledge, appropriate infrastructure and an exit strategy. Like fire, slashing and other fuel reduction methods, cattle can be used to knock down the bulk then moved on and small Gamba clumps sprayed out.
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