Integrated weed management

The aim of integrated weed management (IWM) is to use of a combination of different practices to maintain weed densities at manageable levels.

• 1 September 2008 | Updated 14 October 2011

• Integrated weed management
• Grazing 
• Herbicide application
• Land fallowing
• Biological control

Integrated weed management

An integrated weed management approach to land management combines the use of complementary weed control methods such as:

• grazing
• herbicide application
• land fallowing
• biological control.

The resulting combinations provide the best possible solutions to weed problems for land managers.

By studying the impact of each of the above methods individually as well as in combination, sustainable management systems can be devised to suit different regions and catchment areas.

Grazing

Overgrazing of pastures provides good opportunity for weed species like Paterson’s curse and Scotch thistle to establish. However, combinations of herbicide spraying and grazing (spray-grazing) applied at the correct time of the year, can make weeds more palatable to stock.

This decreases weed populations, encouraging pasture growth and makes pasture plants more competitive.

Herbicide application

Herbicides applied at the wrong time of the year can be ineffective. This wastes both time and money for the farmer.

For example, herbicides used on Scotch thistle in the southern tablelands of New South Wales are much more efficient when sprayed in autumn on rosettes, than if sprayed on mature plants. Mature plants have already produced large amounts of seeds which simply add to the soil seed bank reserves.

Land fallowing

The strategic fallowing of land may provide windows of opportunity for perennial pastures to establish. This helps them out-compete weed species.

A common characteristic of weedy species is that they are generally first level colonisers. That is, when other vegetation is removed by overgrazing, clearing or ploughing and the ground is left bare, weeds establish quickly and reproduce effectively to maintain that niche.

Trials where land is fenced off, show that some weed species have difficulty competing with other vegetation.

Biological control

Biological control agents are generally most effective when established in gullies and rocky knolls of hills. These areas are usually inaccessible and too costly to spray so they can provide a safe haven for agents to retreat to from pastures when there is too much disturbance, such as grazing.

Learn more about CSIRO research on the Biological control of weeds.