Infestation of Scotch broom, Cytisus scoparius.

Scotch broom infests large tracts of land in higher rainfall areas of South-Eastern Australia.

Biological control of Scotch broom

Scotch broom is an introduced shrub which now infests large areas of land once used for recreation, forestry and agriculture.

  • 4 August 2006 | Updated 14 October 2011

Background

Scotch broom, Cytisus scoparius, is a native shrub of Western Europe and has now spread to many temperate areas of the world. It is one of four closely related serious weeds with yellow pea-like flowers.

Scotch broom produces thousands of seeds per plant and these seeds are capable of surviving for up to 30 years in the soil.

There are several methods of controlling Scotch broom and most are suitable for agricultural situations.

Herbicides are effective but expensive and only provide short-term control. Grazing by sheep and goats can prevent further spread, but this type of control is inappropriate for conservation and forestry areas.

Scotch broom is a threat to environmental, forestry and grazing land in higher rainfall areas of southern and eastern Australia. States most affected by Scotch broom include:

  • Victoria
    Scotch broom forms dense thickets that exclude native species, impede access, alter fire regimes and dominate the landscape.
  • Tasmania
  • New South Wales
  • South Australia.

The largest and densest infestations of Scotch broom occur on the Barrington Tops near Scone, New South Wales.

The project

A collaborative biological control program commenced in the late 1980s. The project was run and funded by the Management Committee for the Biological Control of Scotch broom.

There is no agent found that is capable of killing mature Scotch broom plants. Research has been focused on reducing growth and seed production, which should eventually reduce Scotch broom plant numbers.

The Victorian Department of Primary Industries have taken over project management, as CSIRO has no currently active project on this weed.

Biological control

Since the late 1980s three biological control agents have been released in Australia:

  • the psyllid Arytainilla spartiophylla
  • the twig-mining moth Leucoptera spartifoliella
  • the seed beetle Bruchidius villosus.

Only two, the psyllid and twig-mining moth have established well enough to become part of a redistribution program.

Learn more about the Biological control of Cape broom.