Certain principles must be considered before developing an effective weed control plan. These principles will provide a basis for managing weeds.
The six principles of weed management include:
- Control and monitoring
Producers should be aware of existing and potential weed problems on their property and relevant to their location.
Pasture awareness and regular assessment of pasture composition helps to recognise changes in their composition before it is too late. Tools, including MLA's Pasture Health Kit, are available to assist producers in understanding their pasture composition.
Producers should look out for new weed infestations before they become too large and difficult to contain.
Bare or sparse ground, and weak remaining perennial plants, allow weeds to get ahead quickly. Many weeds have seeds that last in the soil for several years, so producers should be particularly wary when conditions have lead to extensive areas of bare ground, such as after a drought.
Producers will find it useful to prioritise weeds and paddocks for control. For example, weeds with some forage value, such as annual grasses, may be contained below an upper limit, while noxious weeds or highly aggressive and invasive unpalatable weeds should preferably be eradicated.
In order to achieve the desired pasture composition in the most cost effective way, producers should evaluate paddock pasture composition. Priority should be given to paddocks with the most aggressive or troublesome weed burden and those with the potential to respond rapidly to management input.
Producers should prioritise efforts and plan a strategy for successful control.
The key components of a successful weed management plan include:
- Preventing weeds coming onto the property in bought-in feed or on machinery.
- Removal of the weeds or reduced weed seed set.
- Restriction of weed germination.
- Encouragement of competition from desirable species.
These objectives can only be met through developing an integrated approach to weed management, which takes into account the growth characteristics of both desirable species and weeds.
- Deliberation - Where am I, which paddock first and where do I want to be?
- Diversity - Which tools and approaches do I need to achieve my goal?
- Diligence - What kind of annual control program should I use and how do I monitor progress?
Preventing new weed infestations and containing the spread of existing weeds will make control easier. This is particularly important following a poor season or a drought.
Weeds are opportunistic colonisers, particularly following lean times when conditions are conducive to their rapid germination and establishment.
Some weed seeds can remain viable in the soil for many years, so successful control (to prevent seeding) may be required for many years. This is why long-term planning and management to keep weeds out and minimise their proliferation is critical.
The start of the growing season represents a critical period in overall weed and pasture management and presents the opportunity to attack weeds before they become well established.
Weed seeds may come on to a property on machinery or fodder. It is important to ensure the source of feed is checked and that machinery is free of seed.
If animals graze a paddock where weeds are seeding, seeds may attach to the wool or skin and be ingested, remaining in an animal's digestive system for up to five days. After grazing such a paddock, place stock into a holding paddock where they can empty out for several days prior to being moved onto better pastures.
Producers should intervene in weed infestations as early as possible - before weeds spread out of control. The start of the growing season provides the opportunity for long-term gains if you are able to attack weeds before they establish a permanent foothold. This is achieved through controlling the massive germination and subsequent establishment of weeds.
If left uncontrolled, soil-based weed seed reserves will be replenished and continually impact on the recovery of perennial pasture species.
Effective weed control must be accompanied by a change in pasture and livestock management. In many cases weeds are a symptom of an imbalance in other management practices.
Where weeds have become a problem, management must change to reduce, and ultimately eliminate, weed infestation. While spraying with chemical may remove a weed for the short-term, unless other management changes are implemented (especially grazing ) to ensure bare areas are removed and competitive desirable species dominate, the weed will return.
It is recommended that producers integrate a range of options that reduce weed seed set and germination and encourage competition from desirable species.
Success is not achieved by simply spraying in one year, but rather is reflected in the complete cessation of seeding and the removal of sources of more seed.
Control and monitor
Monitoring is a critical component in weed management.
An annual assessment of botanical composition will assist producers in detecting changes in pasture composition and signs of decline. A paddock management diary, noting timing and effectiveness of actions, will help producers identify any reasons for change in pasture composition and take early intervention steps to address these.
Producers should always be aware of how effective their weed control measures are and be flexible to adapting these as conditions or results change in the future.
- MLA's publications on weed control:
- 3D weed management:
- Paterson's curse case study and best practice manual
- African love grass case study and best practice manual
- Thistles case study and best practice manual
- Silverleaf nightshades case study and best practice manual
- Chilean needle grass case study and best practice manual
- Serrated tussock case study and best practice manual
- Weeds Australia
- EH Graham Centre for Agricultural Innovation's: Silverleaf Nightshade Best Practice Management Guide
- Tasmanian Department of Primary Industries, Parks, Water and Environment publication: Washdown Guidelines for Weed and Disease Control - Edition 1
- Queensland Department of Agriculture and Fisheries - Invasive plants (weeds)
- Agriculture Victoria - Weeds
- Northern Territory Department of Environment and Natural Resources - Weed management publications
- Primary Industries and Regions SA - Weeds in SA