English or Scotch Broom (Cytisus scoparius) can be controlled to varying extents by herbicides, burning, mechanical clearing and grazing using sheep and goats. Grazing with sheep and goats is effective in pasture situations. However, the limited success, expense and difficulty in controlling English Broom in many areas has resulted in biological control being investigated. Biological control agents for English broom that have been released in Tasmania include the Broom Bud Psyllid and Twig Mining Moth. Neither of these agents are likely to control English Broom on its own but, if they establish, are likely to stress the plants, reduce their vigour and decrease the density of infestations.
It is unknown if these releases have been successful in Tasmania. However, no agent has yet been found to have significant impact on brooms over large areas. Other agents such as Broom Gall Mite (Aceria genistae) may have potential.
Broom Bud Psyllid (Arytainilla spartiophila)
The psyllid, Arytainilla spartiophila, was released in Australia in 1994. Female psyllids cut slits into the stems of English Broom in summer and insert eggs. The following spring, nymphs hatch and feed in the buds and other actively growing parts of the plant for about 2 months.
The winged adults are very mobile and high populations can cause severe damage. Adult emigration occurs readily, even at low population levels, and new bushes are quickly colonised.
Twig-mining Moth (Leucoptera spartifoliella)
The Twig-mining Moth was released in Tasmania in 1995 and again in 1998, but there is no evidence that the moth established from these releases. More were released directly into the field in 2004, and some were used as stock to rear more moths. Moths produced from this culture are being used for field releases to get the broom twig-mining moth widely established in Tasmania.
The main damage done to English Broom by the Twig-mining Moth is through the larvae which burrow into the stems and form tunnels while they feed. Larval feeding activity will not control English Broom on its own, but it has the potential to cause considerable damage and weaken the plant, assisting with control.
More information can be found in the Weed Biological Control Pamphlet No. 9 April 2008