|Because of their ability to compete for light, nutrients and
space, many weeds have devastating impacts on our natural vegetation, decreasing
biodiversity and resulting in habitat loss for our native plants and animals.
Agriculture and amenity are also significantly impacted, with reduced
productivity and large financial costs involved in control. In order to combat
the weed issues present in our catchment a strategic approach to control is
Effective weed management requires a coordinated approach to
weed control and consideration of broader land management objectives and
requirements relevant to your property. Consulting your neighbours, your local
Landcare or Parkcare Group and your local council/Parks Conservation and Lands
ACT is a good first step. It is also crucial that you plan for and carry out
revegetation to avoid causing erosion and ensure habitat is replaced. This
includes identifying appropriate native species for your local area, ordering
adequate numbers in advance, and planning your weed control so that the seasons
are right for follow up planting.
Focusing your attention on preventing new weed infestations
and on the priority weeds for your individual patch of land will ensure that you
save on financial costs and time, conduct a more effective control program and
minimise future infestations.
An essential aspect of successful weed management is a
commitment to ongoing monitoring and maintenance. Keeping an eye out for
unfamiliar species, or outbreaks of known weeds, and controlling them as soon as
possible will prevent the re-establishment of large infestations, making the
initial control program worthwhile and long lasting.
|A coordinated approach
|Coordinating weed control with your neighbouring land managers
will allow for a broader scale strategic approach whereby priority weeds can be
targeted collectively. This weeds package should become a well used resource to
help you understand your important role in protecting our land, water and
vegetation from weeds and in so doing, become good neighbours and stewards for
Landholders at Spring Valley Farm
learning how to distinguish between weeds and natives (Photo:
|Preventing new infestations
Accurate plant identification is essential before conducting weed
control. Take a close look and if you don’t know what it is – don’t
|Preventing the introduction of new weed species is the first
priority in weed management. If you own an urban block, your priority should be
sourcing garden plants that are not prone to invasiveness and avoiding those
plants with known weed potential. Discussing plant selection with your local
nursery can help you identify suitable species for your garden.
If you manage a rural residential block or larger agricultural
property, you will need to implement a range of strategies. Sound land
management practices such as: maintaining property hygiene; sourcing ‘clean’
fodder; quarantining new stock until undesirable weed seed has passed
through their system in the contained area for later control; early
identification of weed species; and coordination of weed control with neighbours
and official land managers will help prevent the introduction of new species and
ensure that management of existing species is effective.
The recent drought has created greater opportunities for weed
invasions due to the feeding of drought fodder in which weeds can be imported,
and due to the increase in bare ground where weeds can readily colonise when
conditions improve. The actions mentioned in the above paragraph should be taken
to ensure full drought recovery.
|There are a multitude of control methods available to manage
Integrated weed management (the use of a combination of a
range of different methods) is the most effective way of managing weeds and
reduces both the reliance on chemicals and the potential for herbicide
resistance. When designing your control program, consideration should be given
to the weed species present on your property, the terrain, the time and
financial costs, and the off-target damage that may occur to native species
present in the area.
In some areas, weeds will be the only vegetation present, and
complete removal would result in a loss of what little habitat the weeds
For this reason, it is essential that all weed control
programs involve revegetation and/or are staged to reduce the impacts on local
fauna and the potential for erosion. A good strategy is to kill the plants
but leave them on site until desirable species establish themselves.
The control method you choose will be determined by a range of
factors, however, a good place to start is assessing the size of the weed
infestation. For example, if you have a small patch of horehound (e.g.
restricted to an area of 20 sq.m.) you may wish to avoid chemical application by
using mechanical control such as hand pulling or digging.
Alternatively, if the infestation is widespread, you may wish
to apply chemicals to kill the plants and then cultivate and sow desirable
species. Natives could be planted for environmental enhancement or if wishing to
harvest a crop or utilise a pasture, a desirable species could be cultivated. If
working over a larger area you might spray the horehound then spread the seed of
a sterile, fast growing grass species (such as sterile rye) which will stabilize
the soil and allow for further chemical control using a broad leaf specific
herbicide to kill out any re-emergent weeds.
|Golden rules for weed control:
- Ensure accurate weed identification to avoid killing
natives incorrectly identified as weeds
- Coordinate weed management with your neighbours, friends
and Landcare or Parkcare Group
- Consider mechanical control as your first option
- If using herbicides, choose the least toxic herbicide and
always follow instructions to prevent damage to the environment/human health
- Apply chemicals when plants are actively growing to
achieve the best results
- Avoid unnecessary disturbance to land, as this provides a
‘seedbank’ for further germination
- Avoid total removal of vegetation in an area as weeds may
provide habitat value: stage removal with re-vegetation in mind
- Conduct controls before the weed sets seed to stop the
- Revegetate treated areas by direct planting and direct
seeding of local species, or staging control and relying on natural
regeneration if seeding plants are available. Use perennial pasture species,
including native grasses, for treated farmland
- Keep a sharp eye out for new infestations and control
re-emergent seedlings immediately
A number of the most common and effective control methods are
explained below. Refer to the individual weed fact sheet and the Weed Control
Calendar for advice on which control methods to select for each species and
information about timing. Parks, Conservation and Lands ACT or your local
council are fantastic resources for specific weed control information, as
is the NSW Department of Primary Industries (www.dpi.nsw.gov.au).
|Mechanical control is the physical removal of a plant. There
are a number of different methods.
- Hand pulling and digging. Suitable for small, shallow
rooted plants. This method can be time intensive and therefore is generally used
for small infestations or sparsely scattered weeds (e.g. weedy tussock grasses
and horehound). A mattock is useful for digging out many weed species.
- Cutting. Using secateurs, a hand saw or chainsaw is
often an effective method of controlling woody weeds and for some species can be
done without the use of chemicals (e.g. pines and Cootamundra wattle).
- Grazing management. Animal selection, stocking rates
and rotational grazing assists weed management by ensuring pastures are not
overgrazed (as this usually results in weed invasions due to the increase in
- Competitive pasture. Promoting competitive pasture by
selecting suitable perennial plant species will help prevent weed establishment
and can assist in reducing existing weed infestations by providing competition
to undesirable species.
- Other mechanical control methods include slashing, ploughing,
tree felling machines and machines that pull out woody weeds.
Mechanical weed control: using a mattock to dig out sweet briar
A range of chemicals suitable for weed control are available
from your local nursery or farm supplies store. When selecting a chemical, it is
essential that you read the label and discuss your choice with the staff - the
label is a legally binding document.
It is especially important to wear protective clothing.
Chemicals are registered for use at certain concentration
rates and for certain locations/application situations. For example, the use of
some chemicals in watercourses can have adverse effects on stream health and
therefore use in an aquatic area is illegal.
Weeds Officer spraying Paterson’s curse and
blackberry (Photo: Queanbeyan City Council)
Once a chemical has been selected, there is a range of safety
considerations involved during the application process. Care must be taken to
ensure there are no negative impacts on human and stock health and that drift
and off-target damage to native or other desirable species is minimized.
Personal protective equipment should be worn at all times.
- Cut and paint. Cutting the plant close to the ground
and then immediately ‘painting’ the stump with a suitable chemical (using a
brush, sponge, or bottle with a small nozzle) is a simple and easy form of weed
control. It is suitable in situations where you are happy for the plant to be
cut down and then left on site or entirely removed.
- Drill and fill/stem inject. This technique involves
drilling a hole, or chipping a notch, into the cambium layer of the trunk (i.e.
the thin layer of generative tissue lying between the bark and the wood), then
immediately applying chemicals. It is suitable for tree species where you want
to kill the plant but do not wish to immediately remove it from the landscape
(e.g. you may wish for it to remain in place for its habitat functions until
other species establish).
- Spraying. Spraying weeds with a hand held spray bottle,
a backpack or a boom sprayer is an effective weed control technique, often more
suitable for larger infestations.
For chemical application rates and detailed control method
explanations refer to the “Noxious and Environmental Weed Control Handbook.”
(NSW DPI 2007).This book is a great resource for anyone attempting to eradicate
weeds from their property and has been developed after a long period of trial
and error – use the experience of the experts to your advantage by referring to
this publication and contacting the department for further advice and/or site
visits to determine the required methods for your situation.
Willow removal after the trees have been killed with chemicals
(Photo: Territory and Municipal Services ACT)
A range of biological controls have been trialled and released
The results have varied from highly effective to little or no
impact. Individual weed fact sheets outline whether or not a biological control
is available for that species and whether there is a need to introduce it to our
area. The NSW Department of Primary Industries and CSIRO continue to conduct
research on biological control agents to identify suitable species for release.
Leaf-feeding beetle, a biological control, eating the leaves of a
young St John’s wort plant