Biological control of weeds

Weeds: a widespread problem

We are all affected by weeds, and not only through their unwanted presence in our backyards.

Weeds – alien or native plants that grow where they are not wanted - are a major threat to both the natural environment and agricultural land we depend on. They can also directly affect the health and well-being of communities across Australia.

Weeds can upend ecological communities, adversely affect rivers, rangelands and forest systems, compete with crops, harm livestock, contaminate produce, reduce water quality and cause human health problems such as asthma.

They are Australia’s most economically destructive type of invasive species. They have cost our economy more than $150 billion over the last 60 years, and continue to cost it around $5 billion per year.

Grain growers alone spend more than $2.5 billion per year on weed control.

A new species of weed takes root in Australia on average every 18 days. All up, more than 3200 introduced plant species are now established in Australia.

We need safe, cost-effective and sustainable methods for weed control to reduce these negative impacts.

Biocontrol to manage weed impacts

Traditional weed control typically involves either the physical removal of the weed or the use of herbicides.

A different, sustainable approach - and CSIRO’s area of expertise - is weed biocontrol. Weed biocontrol utilises a weed’s specialist natural enemies, like insects and fungi, to reduce the weed’s impact.

Termed biocontrol agents, these natural enemies reduce weed biomass, reproduction and/or population density. They are also self-sustaining, making them an effective method for long-term weed control.

Extensive research is undertaken to ensure that only biocontrol agents that don’t threaten desirable non-target species are used.

Our work in weed biocontrol

CSIRO scientists have been doing research on biocontrol of weeds since the 1920s. Working with government, industries and communities, our weed biocontrol programs involve:

• Quantifying the impact of targeted weeds in Australia-Investigating the genetic structure of the weeds and identifying their origin in the native range
• Surveying for natural enemies in the native range and selecting promising candidate biocontrol agents
• Demonstrating that the candidate agents are safe and obtaining approval from the authorities for their introduction in Australia
• Releasing and evaluating the efficacy of biocontrol agents in controlling the target weeds and the flow-on indirect benefits to ecosystems.

CSIRO has many active biocontrol projects underway for both temperate and tropical weeds of importance to Australia.