Bitou bush infestation on bluff
A collaborative project at Iluka Bluff on the north coast of New South Wales is helping to restore a badly degraded, bitou-infested coastline.
Iluka Bluff is next to the largest remaining coastal rainforest in New South Wales, the Iluka Rainforest World Heritage Area.
With funding from the Commonwealth Government’s Natural Heritage Trust, the Iluka Land and Dune Care Group and the New South Wales National Parks and Wildlife Service (NPWS) began working in 1996 to restore the natural vegetation of the Iluka Bluff area.
Most of the 5 ha project site consisted of dense bitou on the Iluka Bluff headland with small areas of remnant kangaroo grass (Themeda triandra) on the eastern and southeastern slopes. The beachfront in the project site was almost exclusively bitou bush as well.
The project involved a number of weed control methods and also saw a new biological control agent, the bitou bush seed fly (Mesoclanis polana), established at the site.
The initial treatments for the dense bitou infestations used a Greencorp team to cut access tracks to clear the way for high volume spraying, which was done by contractors and NPWS staff. Bitou amongst the sensitive remnant grassland was either hand removed or cut and painted, with limited spraying. Several months later, the dead standing mass on the hillside was burnt under controlled conditions. This was done to make follow-up treatment easier, and to destroy a portion of the bitou seedbank and stimulate the remaining seedbank to germinate. Afterwards, mats of cut tea-tree were placed on the bare hillside to help reduce erosion risks. The bitou on the beachfront was sprayed and, after a suitable time, crushed with a tractor. Areas on the hillside and the beachfront with little native regeneration were then planted by the landcare group and other volunteers. Since then the site has been treated periodically to control regrowth of bitou and other weeds.
As a result of this work, native vegetation cover from natural regeneration and plantings is now dominant over 40% of the 5 ha site. The project has complemented other regeneration work in the rainforest and has played a large part in Iluka Bluff being named as New South Wales’ cleanest beach for 2002.
Integrated management
Wherever possible, an integrated management approach needs to be adopted using several control measures. As with most weed control programs in natural ecosystems, natural regeneration or over-sowing with locally collected seed of native species is an important part of the rehabilitation process. If bitou bush is eradicated without follow-up, other weeds such as glory lily quickly fill the gaps.
Rainforests require special treatment
A combination of spot spraying, mechanical removal and biocontrol may be the most appropriate for rainforest infestations. Fire is not recommended because of the sensitive nature of rainforest plants to burning. The number of new weed seedlings in the forest may be low, as bitou bush does not flower well under heavy shade conditions. Treat vigorous infestations of bitou bush surrounding the rainforest.
Disposal
The stands of dead bitou bush left after spraying can be removed by trampling, compacting or, if appropriate, fire. If they are left standing they may provide some protection to dune environments until they eventually decompose. Small amounts of bitou bush removed by hand pulling or mechanical clearing can also be left to decompose but, if possible, the seeds should be removed and burnt.
Legislation
The Australian Quarantine and Inspection Service prohibits the entry of bitou bush into Australia. The plant is declared in New South Wales, Queensland, South Australia, Victoria and Western Australia. Landholders in these states are required to control it. Check with your local council or state/territory government agency about the latest requirements for bitou bush control.
Acknowledgments
Information and guide revisions: Richard Carter (NSW Agriculture/Weeds CRC), Nigel Ainsworth (DPI Vic/Weeds CRC), Jeff Thomas (NSW NPWS), Royce Holtkamp (Agriculture NSW/Weeds CRC), Rhonda James (Coordinator North Coast NSW Bitou Bush Strategy), Paul Downey (NSW NPWS) and John Thorp (National Weeds Management Facilitator). Maps: Australian Weeds Committee.
