How To Manage It?
Best practice management
Control of Cape Broom (Genista monspessulana) is possible by chemical, mechanical, and biological means. However, when mature flowering plants are removed, many seedlings will germinate from the soil seed bank and long term follow-up is critical. Integrated control methods (combining control techniques over time), with long term follow-up is advised for control success. Preventing spread in new areas is the best form of control and weed hygiene should always be employed. A long-term strategic program is required to effectively control Cape Broom concentrating on exhausting the large, long-lived seed-bank and preventing further additions to it. New infestations should be treated prior to plants reaching the flowering stage. Once plants start to produce seeds control becomes more difficult and dispersal to other areas is likely. Treated areas should be regularly checked for regeneration, particularly after fire and soil disturbance.
Chemical control: Larger plants can be cut and painted with a suitable herbicide. Smaller plants can be slashed to control their regeneration and any regrowth sprayed with a suitable herbicide. Various herbicide are effective and available for use, please see, Office of Environment and Heritage (2014) and DPI NSW (2019) for further details. Herbicide application methods are:
Foliar spraying: For the application of herbicide solution to weed foliage in the form of a spray, a common method used for woody plants. Foliar spraying can be used to treat plants of all ages but can be less effective on older plants.
Cut-and-swab method (Cut stump treatment): is when each stem is cut off at ground level and immediately applying herbicide to the cut surface killing the plant to prevent regeneration from the rootstock.
Basal barking: This method involves applying herbicide mixed with an adjuant to the lower trunk or stem of woody plants up to around 50 mm in diameter to a height of 30-40 cm above ground level.
Stem injection (drill-and-fill): Stem injection delivers herbicide directly to the sapwood but is rarely used on brooms, but when used, it is for plants with stems over 50 mm in circumference.
Scrape-and-paint: This method involves scraping away a small section of the bark and applying herbicide directly onto the sapwood. It is an effective but rarely used technique normally used on larger plants.
Splatter or gas gun: splatter guns were developed over thirty five years ago for sheep drenching and has been adapted for weed spraying using chemicals.
Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au.
NOTE: Training is normally a requirement in most States and Territories for all or some of the methods.
Non-chemical control: Control methods are described in detail in Office of Environment and Heritage (2014).
Physical control: Seedlings and smaller plants can be dug out with small tools, or pulled out by hand, preferably when the ground is moist and soft. This is normally used in new infestations that have not flowered or in area after mature plants have been removed, and this type follow-up removes the many new seedlings that would have subsequently germinated. Older senescent broom plants can be cut at or below ground level, sometimes without the subsequent use of herbicide as they usually do not re-sprout or coppice at that stage of their life cycle.
Mechanical control: Removal by clearing is a useful method of controlling large infestations of Cape Broom. Crushing, mechanical pulling plants, or slashing with machinery clears areas ready for follow-up control methods required when mass of germination of Cape Broom seedlings will occurs from the soil seed-bank.
Mulching: Mulching or grooming with a tractor or excavator-mounted mulcher cuts bushes off at ground level and processes them to fine mulch. The mulch provides some suppression of seedling growth leaving a cleaner site after control than some other mechanical methods.
Cultivation: Cultivation with disc or mouldboard ploughs is useful for breaking established roots and for follow-up treatment of seedlings and regrowth in large infestations.
Competition and management: Stock availability, adequate fencing and the establishment of strong pasture grasses are the keys to using grazing to improve broom management.
Fire: Most adult plants are killed by fire, but some are capable of re-sprouting from the rootstock. Although the amount of soil-stored seed may be reduced by burning, effective control of Cape Broom can only be achieved by regular treatment of regenerating seedlings by hand-pulling or herbicide application for 3 to 5 years following fire (Muyt 2001; Department of Primary Industries Victoria 2004, Australian Weeds Committee 2011). Soil-stored seed is stimulated to germinate following fire and may continue to germinate for many years following burning.
Biological control: Cape Broom has also been recognised as a target for biological control through a cross-jurisdictional government process. This allows activities to be undertaken to develop effective biological controls. A number of biological agents have been identified (Department of Primary Industries Victoria 2004; Sheppard & Henry 2012). Two insects, the Cape Broom psyllid; Arytinnis hakani, and the weevil; Lepidapion nr argentatum, both give good control.
Does it have a biological control agent?
YES. One agent has been redistributed for Cape broom after an unauthorised introduction, the Cape broom psyllid (Arytinnis hakani) (Harvey et al 2023).
When does it grow? (lifecycle/growth calendar)
The seeds of Cape Broom (Genista monspessulana) germinate in both autumn and spring and plants produce their first flowers when about two years old. Flowering occurs mainly from August to November. Sometimes a second flowering occurs towards the end of summer. In the heat of spring and summer, seed pods ripen and burst, projecting seeds with considerable force. New growth is produced each winter and spring (Parsons & Cuthbertson 1992).