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An IWM approach to land management combines the use of complementary
weed control methods such as
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 which encourages
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 NSW are much more efficient when they are 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 i.e when other vegetation is removed
by overgrazing, clearing or ploughing and the ground is left
bare, they establish quickly and reproduce effectively to
maintain that niche. Trials where land was fenced off showed
that some weed species have difficulty competing with other
vegetation.
Biological
control: Biological control agents are generally most
effective when they are established in the gullies and rocky
knolls of hills. These areas are usually inaccessible and
too costly to spray so they can provide safe havens for agents
to retreat to from pastures when there is too much disturbance
e.g. grazing.
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