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Weed Spraying and Slashing

Weed spraying in Bunbury and Southwest WA


Common Weeds and their Control

Most plants we think of as weeds are undesirable as they invade native vegetation or become a nuisance to agriculture. Such plants are declared a pest by the Department of Agriculture and Food due to the significant damage they cause to native flora and fauna and to agricultural businesses. In some cases a pest plant will also be formally 'declared' therefore their removal becomes mandatory under law. All land-holders are obliged to control declared plants on their properties. Declarations can be for the entire State, for smaller areas and also right down to individual properties. Some examples of declared plants in WA are:

  • Arum Lily
  • Blackberry
  • Cape Tulip - both the one-leafed and two-leafed varieties
  • Paterson's Curse
  • Variegated Thistle
  • Double gee
  • Heliotrope
  • Cottonbush

As of 2015, there are 80 declared plant pests in WA. Please check out the attached link if you think you may have a declared plant pest on your property. Insert link to Dept of Agriculture and Food - Declared Plants.

Other common nuisance plants that can be invasive and need to be controlled include perennial grasses such as South African Love Grass, Veldt Grass, Paspalum, Kikuyu and Couch; broad leaf plants such as Lupins, Cape Weed and bulbous plants such as Cape Tulip, Freesia and Watsonia.

Every effort must be made to prevent weeds spreading. Weeds invade new areas if they have a competitive advantage over existing plants or if there is some change to the vegetation which allows the invading weed to become established. Weeds can be spread by wind, water, animals, machinery, contaminated garden soils, mulches, stock feed and also human activity.

Weed control methods.

Manual Control
  • o Hand pulling or grubbing - used where weeds are isolated or in small patches.
  • o Cutting flower and seed heads from undesirable plants before seeds set.
  • o Cut-stump control - effective for undesirable trees / shrubs in bushland such as Apple of Sodom, Acacias, Fig trees and Victorian tee-tree.

Controlled burns
  • o This method is of limited use in controlling weeds as it can encourage healthy regrowth of perennial weeds.
  • o Reduces weed seeds on the surface and destroys old stands of weeds however any weeds seeds can blow in to the exposed burnt soils and quickly establish.

Mechanical - Mowing and slashing
  • o Mowing / slashing can be effective on some perennials that do not have an extensive root system. However some plants, such as nightshade and arum lilies are spread by mowing/slashing due to the ability of cut roots to regenerate.
  • o Slashing can be effective for controlling many annual thistles but the timing is critically important.

Biological - rusts / insects
o Biological control uses living organisms either local or introduced to restore the natural balances of the ecosystem by encouraging natural controls. Examples are ladybirds on Aphids, rust on Blackberry, hopper on Bridal creeper and leaf-minor on Paterson's curse.

Chemical control - Herbicides
  • o Grass Selective herbicides control certain annual and perennial grasses in native bush situations for example Fusilade® and Verdict®
  • o Broad-leaf Selective herbicides control certain broad-leaf weeds in grass pastures and bush lands for example Lontrel® and Glean®
  • o Non Selective (Knockdown) herbicides control most weeds: however; desirable plants may be damaged if sprayed, for example, with Roundup®

Integrated Pest Management (IPM)
In many cases control of weeds is best achieved by a combination of methods. In some situations, chemical control offers the only feasible means of weed control. However, using IPM techniques - applying herbicides correctly and only when necessary - will maximise the benefits and minimise the hazards. Examples are:
  • o Burn sections of bushland infested with South African Lovegrass. Wait a few weeks then spray the regrowth before the native vegetation has regenerated. If there is a small amount of Lovegrass that appears after the spraying they can be pulled out or carefully spot sprayed. Follow-up control is very important or the infestation will continue.
  • o Slashing degraded sections of bushland will also promote healthy regrowth of the target grasses, which allows herbicides to work more efficiently. Healthy weeds respond to herbicides.
  • o Spot spray weeds and replant area with native vegetation. This is a good method to protect remnant sections of bush and increase the native vegetation each year.
  • o Over-spray bush areas with a grass selective herbicide to control annual grasses and hand pull broad-leaf weeds such as Lupins, Cotton-bush, Fleabane and wild Radish.
  • o Some Grass selective and Broad-leaf selective herbicides are compatible to mix together and can be sprayed over native vegetation to control annual grasses and some broad-leaf weeds. The correct application rate must be achieved and all spray equipment must be carefully calibrated. Other weeds not controlled by a herbicide blend may be hand pulled or spot sprayed with a non-selective herbicide.


Effective weed control depends on being able to identify the problem. Seek advice from local authorities, land-care organisations, consultants, or check the following websites: Pestgenie; Weeds in Western Australia; Western Weed or CONTACT MAINSPRAY.

Some useful sites to Google for weed spraying and control are:-
  • Pestgenie
  • Weeds in western Australia
  • Western weed


  • Mainspray caters for all types of weed spraying, slashing and mowing in Bunbury and the South West of WA.

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