Koster's curse (Clidemia hirta)

Also known as: clidemia, soapbush, hairy clidemia

Profile

Impact

Koster’s curse is a highly invasive perennial shrub that rapidly forms dense thickets, invading forests, plantations and pastures and smothering native vegetation. It is capable of growing in undisturbed areas, giving it the potential to cause widespread damage to sensitive native vegetation. In disturbed areas it will increase rapidly once introduced.

Distribution

Koster’s curse originates from South America, from Mexico, through to northern Argentina and the Caribbean Islands. In its native range Koster’s curse is not found in forests, yet it is a highly invasive weed in tropical forests where it has been introduced.

Koster’s curse is considered a serious weed in Hawaii, tropical Pacific islands (Fiji, Samoa and Vanuatu), Southeast Asia (Thailand to New Guinea) and the Indian Ocean islands (Seychelles, La Reunion, Mauritius and Madagascar). It has become naturalised on the Indian subcontinent (India, Bangladesh, Bhutan, Nepal, Sri Lanka and Pakistan) and in Tanzania.

In Australia, an infestation was first detected in 2001 near Julatten in far north Queensland. It is thought to have entered the country from contaminated packaging material. This infestation is currently subject to a national eradication campaign.

Koster’s curse has not been detected in New South Wales (NSW), but has the potential to invade the humid northern coastal areas.

Spread

In ideal conditions, each plant is capable of producing thousands of seeds per year. Dispersal of seed is mostly by berry eating birds, but can also be spread by contaminated soil movement.

Seeds can remain viable in the soil for at least four years. Seedling establishment is very successful and plants can reach full maturity in less than twelve months.

Description

Koster’s curse is a bushy perennial shrub covered in reddish-brown bristly hairs. It will generally grow to around 2 m high, although it can grow up to 5 m in moist, shady conditions.

Key identification features

• Leaves are hairy and occur in opposite pairs along the stem. They are widest around the middle, 5–14 cm long and 4–7 cm wide with toothed margins. The upper surfaces are a bright, shiny green, and the undersides are paler. Five prominent veins run down the length of the leaf, with many obvious cross veins occurring between.
• Clusters of 6–20 small flowers occur in the leaf forks or at the end of branches. They are 1–1.5 cm in diameter with 5 white or pinkish petals. Flowers occur all year, except in dry conditions.
• Each flower produces a reddish purple berry 4–5 mm in diameter which contains over a hundred very small seeds—about 0.6 mm in size.  Berries are hairy and turn dark purple when mature.

Habitat

Koster's curse prefers tropical climates with an annual rainfall over 1200 mm, growing in both shaded areas and full sunlight.

Acknowledgements

Reviewed by:  Rod Ensbey  Edited by: Elissa van Oosterhout, Birgitte Verbeek

References

Queensland Government—Department of Employment, Economic Development and Innovation (2011) Fact sheet—Koster’s curse Clidemia hirta

Hosking JR, Sainty GR, Jacobs SWL & Dellow LL (in prep) The Australian WeedBOOK.

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Control

If you suspect you have found Koster’s curse, your local council weeds officer will assist with identification, removal and eradication.

Herbicide options

Contact your local council weeds officer for control advice for Koster's curse (Clidemia hirta).

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
All of NSW	Prohibited Matter A person who deals with prohibited matter or a carrier of prohibited matter is guilty of an offence. A person who becomes aware of or suspects the presence of prohibited matter must immediately notify the Department of Primary Industries

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Reviewed 2017