The annual cost of weeds to Australian agriculture has been estimated at more than $4 billion. The figure primarily represents production losses and control costs, as the cost of weeds to the environment, especially to biodiversity, is largely incalculable.

More than 1400 exotic plant species have become naturalised in South Australia, of which several hundred impact significantly on agriculture, the natural environment (including freshwater systems) and communities. About 65 per cent of weeds are escaped garden plants, many of which are still traded.

About 110 species are declared under the Natural Resources Management Act 2004 including weeds such as bridal creeper, salvation jane, wheel cactus, caltrop and African boxthorn. Branched broomrape is a parasitic weed in the Murray Mallee region and is the subject of a national eradication program. It can parasitise a diverse range of broadleaved vegetable, pulse and oilseed crops, pastures and native plants, and also threatens cereal exports as a seed contaminant.

Declared plants

Landowners have the legal responsibility to control declared plants. South Australia’s eight regional Natural Resources Management Boards coordinate and enforce local and regional control programs for declared plants. Declarations of plants (including local requirements for control) vary between and within NRM regions.

Priority species for regional control programs also vary depending on the threats a weed poses in particular localities, whether it is a new invader or widespread, ease of control, and time of year.

For information on the plants declared for enforced control in your area, please contact your regional NRM Board.

• Declared Plants of South Australia Brochure (3.4 MB PDF file, new window)
• Aquatic weeds of SA brochure (2.4 MB PDF file, new window)

Statewide management plans

Plans for specific weeds have been prepared to aid in their future management in South Australia:

• State Opuntioid Cacti Management Plan (2.48 MB PDF file, new window)
• Manament plan for Silverleaf Nightshade in South Australia (900 KB PDF file, new window)

Climate change and weeds in SA

In 2009 CSIRO’s Climate Adaptation Flagship produced for Biosecurity SA a report into the implications of climate change for weed management in South Australia. The main report and case studies are available for download as pdf documents below.

The report reviews the literature on weed ecology and management in relation to climate changes and outlines projections for the climate of South Australia and what this means for weed management planning.

The report identifies that increasing temperatures will allow many weed species to invade further south and east in South Australia, with particular increases in the susceptibility of the South East and Kangaroo Island to invasion from weeds suited to warmer, drier climates.

Areas of potential biosecurity threat were identified by matching the climate of South Australia, both for the recent past and for 2080 with similar climatic regions of the world, using the computer model CLIMEX. However, new species of invasive weeds are most likely to come from other mainland states of Australia.

Thirteen case studies of weeds, either already present in South Australia or ‘alert' species not currently in the state, were undertaken. Each of the case studies includes a set of weed-specific recommendations aimed at identifying adaptation options.

The study was co-funded by Biosecurity SA through the State NRM Program, and CSIRO.

• Climate change and invasive plants in SA, Main Report (2.4 MB PDF file, new window)
• Climate change and invasive plants in SA, Case Study (5.1 MB PDF file, new window)

Preventing weed spread

To prevent the spread of particular serious weeds, their sale in South Australia has been prohibited under the Natural Resources Management Act 2004:

• List of weeds banned from sale in South Australia  (312.5 KB PDF file, new window)

Weed hygiene practices are an important tool in combating the spread of weeds. See the brochure below for practical and effective tips on how you can help protect primary producers and the environment by preventing weed spread:

• Preventing weed spread brochure (1.3 MB PDF file, new window)