Bitou Bush

This article was written by students in a grade school class in Australia.

Origin

Bitou Bush (Chrysanthemoides monilifera) is a native South African plant that was introduced to Australia in the late 19th century. It is thought that the bush was transported to Australia in the ballast of merchant ships.

Establishment

The Bitou bush was firmly established in the Newcastle area by the 1920s. Its survival in the infertile dunes of Stockton Bright led to the identification as a potential solution to issues of dune instability. For the next three decades Bitou was planted along the southeastern coast of Australia. By 1982, the Bitou bush could be found along 60% of the New South Wales coast.

Negative Impacts

In 1971 the negative impacts of the plant were identified. Although its use was withdrawn the damage was already extensive. The Bitou bush was able to successfully compete with native species found on the dunes.

Causes

The seeds of the Bitou Bush are produced in great quantities, making the spread of the bush rapid and difficult to control. These seeds encourage bird life on the dunes, and due to migrational habits, the seeds are carried up and down the coast. The seeds of the bush can survive extreme conditions, including fire, before germination, by remaining in the soil.

The Bitou bush, as an introduced species, has no natural diseases or predators in Australia. It also quickly dominates a dune system, killing off native species. This creates a monoculture on the dunes, which decreases biodiversity and resilience to stresses. For this reason, the plant's eradication is difficult and must be entirely managed by humans.

Large and deep root systems are a key feature of the Bitou bush. It was for this reason that the plant was originally used on the dunes; to stabilise the sand dune systems. However, this means that the dunes onto which they are planted become dependent on the bush for stability.

Management

Due to these negative impacts, the Bitou bush poses a significant management problem. It is extremely difficult to remove, and due to the monoculture it creates, once they are removed, the dunes are left exposed and unstable. The plants must be removed by hand as all the roots must be removed. Although the dunes will be left unstable, the eradication of the Bitou bush is essential due to the severity of the long term impacts it would have on the dune ecosystems. To counteract this instability, native vegetation must be planted in its place.

The Tortrix Moth

The Tortrix Moth, or the 'leaf-rolling' moth, could be a biological control for the Bitou bush. The larvae of the moth feeds on the leaves, stems and surfaces of Bitou shoots, preventing new growth.

The Commonwealth Scientific and Industrial Research Organisation (CSIRO) has conducted extensive tests which demonstrate that the moth does not affect other native species. Releases of the Tortrix moth have been made up and down the east coast of Australia since 2001.

Seed Fly

The larvae of the Seed Fly feed on the developing seed of the Bitou bush, leading to major reductions in Bitou bush seed production. The Seed Fly was initially introduced into Port Macquarie in 1997, and has since been established in several dune ecosystems. In Australia, the Seed Fly has almost halved the seed production of the Bitou bush.

Rust Fungus

Rust Fungus attacks the stems and foliage of the Bitou bush. The rust affects the plant in a way that the bush can produce little or no fruit, and will consequently die within one to four years. CSIRO has also concluded that the Rust Fungus will not have an impact on native species.