Genista monspessulana (Montpellier broom)

Unpublished work in Australia, New Zealand and the USA on broom management with goats, suggests this is a potential option. It can be effective on disturbed/agricultural land where native regeneration is not being encouraged. Meat or dairy goats should be used because these are the easiest to handle and cannot jump the fences. Goats can be trained to be quite selective at least within the vegetation structure, for example they can effectively strip flowers. Goat management may require the provision of access trails and follow-up herbicide treatments on resprouts once the goats have been moved on. Burning uncut broom in late spring/early summer can be used successfully (Boyd, 1994), although appropriate conditions for an effective burn are hard to obtain safely. Burnt sites showed >80% loss in seedbank density (Alexander and D'Antonio, 2003). Reburning the same site 2-4 years later may also help if there is a sufficient fuel load and the frequent fires do not prevent native bush regeneration. However, reburning does not further reduce the seedbank (Alexander and D'Antonio, 2003). Fire is best used as part of an integrated strategy and post-fire monitoring is a key requirement.

Mechanical removal of G. monspessulana is labour intensive and so best applied to small infestations amongst desirable vegetation. Mower or bush hogs are sometimes a viable option for monospecific stands but there are often problems of accessibility. Slashing, whacking or brush cutting are other alternatives (Archbald, 1996). Bulldozing is not recommended due to the soil disturbance generated and the effect this has on burying and prolonging the seedbank. Cut individuals can resprout if not cut at ground level. For individual large plants, weed wrenches assist targeted removal, but can disturb the soil prolonging the need for monitoring for regeneration (Bossard, 2000). Hand removal of individuals prior to seed fall in sensitive areas, particularly for isolated individuals at flowering is an effective strategy in National Parks where the walking public can be trained to recognize and remove broom. Mechanical control does not deal with the long-lived seedbank and so integrated strategies associated with reseeding desirable species, or at least allowing those present to seed effectively, are often required (Bossard, 2000). Over-sowing with a perennial grass layer has been suggested for other brooms and may also be effective following fire. All forms of mechanical removal require monitoring of treated areas for regrowth from stumps and the seedbank. Sites should be visited once every 1-2 years after treatment in late spring for 5-10 years and every 2 years thereafter to treat any new patches and flowering individuals prior to seed set.

The main chemicals used to control brooms are picloram, triclopyr, glyphosate, fluroxypyr and metsulfuron (Parsons and Cuthbertson, 1992). Specific chemicals are appropriate for specific situations, such as proximity to water courses. The addition of some surfactants to glyphosate and metsulfuron increase the level of control achieved by these chemicals. Triclopyr ester in Hasten or Penevator oil in low volume basal bark application with a wick has proved very effective at killing mature plants (Bossard et al., 1995). Herbicide injection (drilling, filling and frilling) has also been trialed (Gillespie, 1991). Chemical control of G. monspessulana is most usually applied as a high-volume foliar spray. Applications need to be made in periods of active growth after flower formation, but before seed dehiscence. Seedlings are least resistant to hormonal herbicides at the 10- to 15-cm size (Bossard, 2000). Regular follow-up spraying is essential for effective control, but standing dead biomass also presents a major fire hazard.

Work on the biological control of G. monspessulana started in 1998. So far only one agent, Arytinnis hakani, has received a release permit and, as yet, only in Australia (Sheppard, 2003). Several other species are being considered. No releases have been made. Bruchidius villosus has recently been introduced into a number of countries to control Cytisus scoparius (Syrett et al., 1999) and is also likely to feed on G. monspessulana.

Only two studies have been found that look in depth at possible management strategies for G. monspessulana and both these are unpublished. The first relates to an experiment carried out in Jackson State Experimental Forest in California, USA (Bossard, 1995), while the second was a similar study carried out in the Adelaide hills, South Australia (Lloyd, 2000). The results were similar. Management is most effective using fire-based integrated weed management in areas that cannot wait for the long-term biocontrol solution. Before burning, curing the broom using herbicides (triclopyr basal applications or glyphosate to protect natives) increases fire intensity, thereby stimulating or killing a maximum amount of the resident weed seed bank. Fire is most effective on pre-sprayed or slashed broom because this also keeps fire low to the ground. Lloyd (2000) also found that smoke stimulated seed germination in plots not directly affected by the fire. Targeting the seed bank in this way with fire achieved 85-95% losses of G. monspessulana in both trials even with quite low intensity burns. Follow-up treatments must be carried regularly to kill regenerating plants just before seed set, i.e. about 2 years after the fire. Such follow-up treatments kept broom cover to <5% after 3 years in California. Many land managers perceive management with fire as too risky and also little is known about the effects of such control burns on the native species that should be encouraged to replace the weed.Best practice in broom management will require a specific strategy for each situation. Areas should be designated for containment versus treatment where resources are limiting. Fire or goats can be the basis of integrated broom management strategies depending on the situation. Without these options (e.g., in containment areas) biological control remains the only solution. All successful management requires a communication strategy to explain and encourage adoption and adaptive management (trying new ideas in parallel to traditional wisdom) should be encouraged at all times.