Using glyphosate on gamba grass

The herbicide provided through the Gamba Grass Assistance Program is called glyphosate. 

How to mix glyphosate

You will be provided with Ken-up Aquatic 360, which contains 360g per litre of glyphosate as the active ingredient.

You must dilute the glyphosate before you apply it to gamba grass. 

When you dilute glyphosate you must use only the described ratio of water to herbicide. 

For glyphosate 360g/L provided, mix 1 litre of concentrate with 100 litres of clean water for a 1% ratio.

Ratios that are too strong can burn leaves and may not kill the whole plant.

Ratios that are too week may not kill the plant.

You must do all of the following:

  • mix herbicide with rainwater, tap water or good quality bore water
  • not use creek or dam water that may contain clay or organic matter
  • consider adding a wetting agent to help the glyphosate get through the hairy surface of gamba grass leaves
  • use marker dye to show if you missed any weeds.

Planning to spray your property

You should consider the following when you are planning to spray your property:

  • spray only when leaves are green and at least 40cm long - glyphosate can be absorbed only by growing leaves and stems
  • spray early in the Wet Season, before it reaches full height - this gives better results for less herbicide and effort
  • before spraying, consider removing tall, dry grass stems and encouraging new growth of mature gamba grass - controlled burning or slashing may help with this
  • allow time for slashed, mown, grazed or burnt gamba grass to grow new leaves before spraying
  • always spray before seeding
  • gamba grass is still susceptible to herbicide when flowering. 

How to spray

The following is a checklist for how and when to spray:

  1. Adjust your nozzle to produce medium to heavy size droplets so you can get full coverage of the plant while reducing spray drift.
  2. Coat the entire plant - each stem of a gamba grass tussock is an individual plant, if any stems are missed the plant can recover.
  3. Spray until herbicide drips from the leaves to make sure it gets through the fur on the leaves.
  4. Don't spray in windy conditions to avoid damage to non-weed plants nearby.
  5. Use only aquatic approved glyphosate near watercourses to avoid harming plants and animals in the water.
  6. You should spray in the mornings, and at least an hour before rain as it takes an hour for plants to absorb the herbicide.

Where to prioritise

You should prioritise fire risk areas. 

All gamba grass within 50m of houses, sheds and other infrastructure should be controlled and removed.

Control all gamba grass in fire access trails. This also prevents spread to adjoining properties.

Eradicate isolated plants and outbreaks to prevent establishment in new areas.

Control plants which are likely to cause further gamba grass spread, such as on the edge of tracks.

Ensure your control efforts do not contribute to unintended seed spread.

Follow up after your spray

If plants have not wilted and yellowed within four to seven days you will need to spray again.

Check all treated areas for missed plants, regenerating plants and new seedlings

You may need three or four rounds of spraying for good results in the first year of control.

Follow up control in subsequent years will also be necessary.

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Last updated: 28 November 2017