Gamba grass

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Free help to control gamba grass

You can get free herbicide, spray equipment loans and weed management advice from the Northern Territory Government to help control gamba grass in the Top End, including Katherine.

The 2018 to 2019 program is now closed. The program will re-open for the 2019 to 2020 wet season.

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A herbicide is a chemical that destroys or slows the growth of plants, especially weeds. The herbicide used to control gamba grass is called glyphosate.

You must correctly use herbicides as they can cause immediate and long-term illnesses.

There are laws and instructions you must follow when using herbicides, these include Commonwealth and Northern Territory law.

Go to the Australian Government website to read about Commonwealth laws.

Read the NT Agriculture and Veterinary Chemicals (Control of Use) Act 2004.

Follow the instructions

Under the law, you must follow instructions on the herbicide label.

For more advice on using herbicides go to page eight of the NT Weed Management Handbook (1.3 mb).

You should read the safety data sheet of any herbicide you use for information including:

  • potential health effects
  • first aid
  • personal protective equipment
  • spill and disposal procedures.

Using herbicides in the environment

You should follow these guidelines for safe herbicide use:

  • don't spray plants other than declared weeds as glyphosate can kill plants other than gamba grass if it comes into contact with them
  • don't spray in windy conditions as spray drift can damage plants you are not targeting
  • don't contaminate dams, waterways or sewers with glyphosate.

Poisons advice

The Poisons Information Centre can give you advice in case of a medical emergency.

Phone: 131 126

The herbicide provided through the Gamba Action Program is called glyphosate.

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

Go to a copy of the Ken-up Aquatic 360 herbicide instructions (548.8 kb).

You can find a copy of the herbicide's safety data sheet on the Kenso Corporation website.

How to mix glyphosate

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 15m of roads, tracks, property boundaries, houses, sheds and other infrastructure must be controlled.

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.

There are two types of spray units available for you to borrow for free to help control a gamba grass infestation on your block.

Slide-on spray units can be used from the back of a quad bike or ute.

Quikspray units that may be better suited to larger or hard to access gamba grass infestations are also available.

Slide-on spray units

Slide-on spray units:

  • are lightweight and small
  • can fit on the back of a utility vehicle
  • come in 50, 100 or 200 litre sizes
  • have 6m of 8mm hose
  • use a 12 volt car battery - the battery is not included.
How to use a slide-on spray unit

When you fill the tank make sure half the final volume of water is added to the tank before you add concentrated herbicide. This allows proper mixing.

All spray equipment including tanks must be rinsed and flushed with clean water before you return them.

Quikspray units

You should book in advance through the Weed Management Branch or Bushfires NT in Batchelor.

Quickspray units:

  • are large and require a trailer or ute
  • come in 200 or 600 litre units
  • have options of twin reel sprayers
  • have a retractable 50m or 100m hose
  • run on unleaded petrol.
How to use Quikspray equipment

When you fill the spray tank make sure half the final volume of water is added to the tank before you add concentrated herbicide. This allows proper mixing.

Do not adjust the settings on the Quikspray unit. These have already been set to minimise the risk of spray drift.

Only use unleaded petrol for the pump motor for the tanks.

Make sure the hose does not come into contact with your car, pump motor exhausts or hot or sharp objects.

Don't over-retract the hose, as the stopper can be damaged.

Make sure you secure spray guns before transporting the unit.

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Last updated: 05 June 2019

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