Bitou bush was once used to stabilise sand dunes, but has now become a significant weed in coastal areas.
Background
Bitou bush, Chrysanthemoides monilifera subspecies rotundata, is a sub species of Chrysanthemoides monilifera and native to southern Africa.
It is rated as the worst pest plant in the Australian coastal environment, restricting access to beaches and destroying native bushland.
Where bitou bush invades the impacts include:
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a decline in native plant communities
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a decline in floral biodiversity
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changes in the diversity of birds, mammals and ground-dwelling insects
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harbouring pest animals like foxes and introduced birds which disperse the seeds.
Bitou bush first found its way to Australia in 1908, dumped as ballast from ships on the banks of the Hunter River in New South Wales (NSW).
The species was then recognised as an effective coloniser and deliberately planted for soil and dune stabilisation from 1946-68 along the coast by the Soil Conservation Service of NSW.
Bitou bush currently infests the coastal areas of:
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NSW
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southern Queensland
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Lord Howe Island.
By 1982, bitou bush was found along 60 per cent of the NSW coast (approximately 660 km) and was the dominant species along 220 km of that coast.
Biological control agents, like the tip moth, seed fly and leaf-rolling moth, complement each other and increase pressure on bitou bush, making it less competitive.
There are six sub species of C. monilifera in South Africa. Fortunately only one other aside from bitou bush occurs in Australia, this being boneseed, C.m. monilifera.
Boneseed is now found in:
Biological control
Biological control of both Chrysanthemoides species in Australia began in 1987, and there have been eight biological control agents released.
Two agents for bitou bush are well established and require no further distribution.
These are:
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Comosotolopsis germana, the bitou bush tip moth, which feeds in stem tips destroying developing leaves, buds and flowers and reducing seed production. It is now widely established in the field but does suffer heavy predation and parasitism at some sites.
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Mesoclanis polana, the bitou bush seed fly, which is now widely established. The larvae feed on developing seed, causing major reduction in seed production.
A third agent released in Australia, the leaf-rolling moth, Tortrix species, is the most damaging on bitou bush.
This project involved a collaboration between CSIRO Entomology and NSW Agriculture (now NSW Department of Primary Industries: Agriculture) to rear, release and evaluate the performance of the leaf-rolling moth.
There is currently no ongoing project for the biological control of bitou bush. However, there is now new activity focusing on a rust that affects boneseed (and the closely related bitou bush).
Read more about Bitou bush biocontrol agent: the leaf-rolling moth.
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