Preventing the spread of weeds is difficult, as many weeds have physical characteristics that allow their seeds and other reproductive parts to be easily transported over long distances.
Weed seeds 'fly' on the wind, ride river currents, hitch a lift on shoes, clothing, vehicles and machinery, and attach themselves to pet fur, livestock and wildlife. Seeds and plant parts can also hide in soil, water, mulch, animal feed and herbivore faeces.
Whenever people or animals move through weed-infested areas, there is a chance that weeds will be spread to new areas.
Highly invasive weeds threaten grazing lands, waterways, national parks and urban environments. In Australia, the cost of weeds on agriculture has been estimated at $4 billion a year (excluding the impacts on the environment and community).
One of the most cost-effective ways to control weeds is to stop them spreading and eradicate new infestations.