Weed management — protecting the pasture investment

Weeds are estimated to cost Australian livestock industries $2.1 billion per annum in control costs and lost production.

The following principles provide a basis for managing weeds.

  1. Awareness - be aware of existing and potential weed problems.
  2. Detection - be on the lookout for new weed infestations before they become too large and difficult to contain.
  3. Planning - prioritise efforts and plan a strategy for successful control.
  4. Prevention - is better than a cure, so preventing new weed infestations and containing spread of existing weeds will make life easier.
  5. Intervention - and do it early. Controlling weeds now rather than later will prevent them spreading out of control.
  6. Control and monitor - as always, monitoring is a critical component in weed management. Managers need to gauge how well they are controlling weeds and re-plan their efforts for the future.

Use the 3D weed management approach to minimise the impact of priority weeds on pasture and livestock production. The '3Ds' of weed management are:

  • Deliberation -  consider the current weed problem and the desired level of weed control.
  • Diversity - use a combination of tools to control weeds.
  • Diligence - continue to manage the weed problem to keep it at the desired level of control.

Apply the '3Ds' of weed management to increase pasture competitiveness while reducing the proportion of weed species in the pasture.

Ideally, weed management in pastures is undertaken through a weed replacement approach - encouraging desirable pasture species to replace and exclude weeds.

Fire is a strategic tool to manage weeds in northern production systems.

What constitutes a weed?

Pasture weeds are not always easily determined, as most weedy species have some feed value at some point in their life cycle.  

This complicates weed management, as the weedy status of a plant depends on the time of year, its location, the livestock enterprise and management objectives.

Weed impact varies according to season, climate, soil type and, most importantly, the management of the pasture. However, weeds generally have one or more of the following characteristics:

  • poisonous to livestock
  • produce plant parts that affect animal health, prevent grazing or reduce the value of animal products (eg grass seeds that damage the skin or meat)
  • lower digestibility
  • occupy space and resources that could otherwise be used to grow more productive and desirable species
  • rapidly spread to neighbouring areas
  • costly to control

Undesirable or ’weedy’ species in pastures generally fall into one of the following four categories:

Know your weed

Recognise pasture species and become familiar with the life cycle of key weed species, particularly seed production and recruitment periods. 

A clear understanding of a weed’s life cycle can help to identify the weed’s strengths and weaknesses, assisting the development of an appropriate management strategy.

Identify:

  • how weeds are transported and spread
  • where each species prefers to grow and the type of grazing management that encourages its growth
  • the relative lifespan (hardseededness) of seeds of different species.

Manage in response to season

Favourable seasons offer greater flexibility for weed control. Pastures generally respond better to management treatments under favourable conditions as they are actively growing.

In poor (dry) seasons, pastures may be stressed, dormant or inactive and management tactics to control weeds and encourage desirable species will therefore have limited impact.

Adjust management according to the prevailing seasonal conditions.

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