Environmental and Noxious Weeds

A ‘weed’ is best described as a plant that is growing out of place or where it is not wanted.  Many environmental and noxious weeds were accidentally introduced to Australia as garden plants that have now escaped to become weeds.  Those plants with potential to spread widely and to have a detrimental effect on the environment or the economy are declared as noxious weeds.  The declaration of noxious weeds varies across New South Wales.  To find out which weeds are declared noxious in your area, contact the Weeds Officer at your Local Council or visit the NSW Department of Primary Industries website (http://www.dpi.nsw.gov.au/agriculture/pests-weeds/weeds).

Responsibility for the management and control of noxious weeds lies squarely with the property owner, or where a property may be rented or leased, the occupier of the property.  It is not the responsibility of Council to manage and control weeds on private property, however in certain circumstances Council can instruct and enforce property owners or occupiers to undertake weed control activities.

It is also important to be aware of environmental weeds.  While not declared noxious, environmental weeds can still invade and cause harm to native vegetation and waterways.  Environmental weeds can include both exotic plants and native species growing outside their natural range.  Environmental weeds commonly include lawn species (eg Kikuyu and Buffalo) and other garden plants that escape and spread into native bushland where they out-compete and replace native species (eg Morning Glory, Wandering Jew, Cassia, Camphor Laurel). 

Impacts of Weeds

Weed invasion is one of the most serious conservation and land management problems in Australia and has a significant impact on the health and survival of crops, pastures, native vegetation and wildlife.  Weeds compete with native and agricultural plants for nutrients, moisture and light.  Weeds also prevent natural regeneration of native species, reduce wildlife habitat, change the movement and quality of water, increase soil erosion and change fire behaviour.  Weeds can also poison the soil, and be toxic to humans and animals.

Methods of Weed Control and Integrated Weed Management

There are five key methods of weed control that are generally practiced. 
These include:

    1. Biological Control: the absence of natural pests and diseases is the reason that many introduced plants have become weeds in Australia.  Biological control involves using natural predators to suppress a weed and generally requires natural predators to be introduced into Australia from another country.  However, because Australia does not want to introduce another ‘Cane Toad’ or other noxious pest species, the introduction of a biological control agent is often a costly and time consuming process.
    2. Chemical Control: involves the use of herbicides to control or eradicate weed species.  However, there is more to using chemicals than just following the label on the container.  You need to consider wind speed and direction, the possibility of rain and the proximity to people, animals and waterways.  Chemical control may not be an appropriate control method for all weed species, while some chemicals or their application in certain locations (eg waterways) may require a license.
    3. Physical Control:  physical methods include tillage, burning, mowing, and hand pulling.  Physical control is an important part of property weed management strategies, particularly for removing new weed infestations in their early stages.
    4. Cultural Weed Management: involves land management practices which suppress weed growth and production, and promote desired plant species growth.  Aspects of cultural control include preventing the spread of weeds between fields or sites through isolation of weed zones, companion planting, and the use of mulches (eg straw, leaf litter & woodchip). You may find different, practical examples of cultural weed management at your local Landcare site.
    5. Integrated Pest Management (IPM): Rather than relying on one particular control method (which may not be effective), IPM uses a combination of all of the above control methods to control or eradicate weeds. It aims to minimise disturbance to, and the use of, chemicals in the environment.  IPM may also consider the integrated management of multiple species, including animal species which may act as a vector for the spread of weed species.

What You Can Do On Your Property

  • Know your weeds and their control methods, otherwise you could be making more work for yourself or make the infestation worse! Contact your local council weeds officer or visit the Weeds Australia Website (www.weeds.org.au) if you are unsure.
  • Work from good areas to bad ones, and from upstream to downstream (to prevent seeds being washed down to newly cleared areas!).
  • If you are in doubt of a plant’s identification—don’t pull it out, ask your Local Council Weeds Officer or your local Landcare group.
  • If the infestation is too big to eradicate, remove flowers and seeds to stop it from spreading—birds and other animals, wind and water can spread weed seeds over great distances!
  • Gradually remove weed infestations to allow local native wildlife to find other homes and habitats—even weeds can provide a home and food for animals.
  • If you can’t be sure that imported fodder is weed free, then set aside an area for its storing and feeding to livestock.
  • Stop water and fertilisers running from your garden into other areas such as bushland.  Nutrient enriched soils promote weed growth.
  • Work with your neighbours to control weeds—it will allow you to target a larger area and prevent re-infestation from neighbours properties.

Local Council Weeds Officer
NSW Department of Primary Industries
Local Landcare or Bushcare Group


Copyright 2011 HCCREMS