Kangaroo Island
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Caltrop (Tribulus terrestris)

Caltrop (Tribulus terrestris)

High Risk Weed for Kangaroo Island

Caltrop is an Alert Weed for Kangaroo Island. Notify the Kangaroo Island Landscape Board. Early detection and control are the best way to prevent the next widespread weed. 

It is a declared plant for South Australia. 

THE SITUATION AND WHAT TO DO

Caltrop is a low-growing annual summer weed that is declared pest palnt in South Australia and is widely naturalised across Australia, particularly in arid and  semi-arid climates. It is mostly found in disturbed areas, including roadsides, tracks, cropping land, lawns, and bare soil areas. 

On Kangaroo Island, caltrop is currently known to occur within the townships of Penneshaw and more recently American River and has previously been recorded at Kingscote and Emu Bay. The source of these infestations is likely from seeds transported in the footwells of vehicles, visitor shoes and clothing travelling from areas where caltrop is common. Caltrop has also been introduced to the island as a contaminant in lupin stock feed.

Caltrop can grow very quickly, particularly after summer rain. Plants may begin producing hard, spiny burrs within a week. These burrs easily attach to shoes, tyres and animals, allowing the weed to spread rapidly to new areas. Early identification, reporting and control are essential to prevent further spread and stop new infestations becoming established on Kangaroo Island.

You can help keep Kangaroo Island free of caltrop by:

Caltrop (Tribulus terrestris)

DESCRIPTION

  • Growth form: Prostrate (spreading) annual plant forming flat mats up to several metres across.
  • Leaves: Small, opposite leaflets giving a fern-like appearance.
  • Flowers: Small, bright yellow five-petalled flowers.
  • Fruit: Hard, woody burrs (up to 1000/plant) with hard sharp spines that readily attach to tyres, shoes, animals, and machinery.
  • Seed: 10 to 20 seed per burr equalling tens of thousands of seed per plant and can remain viable up to 5 to 6 years. 

IMPACTS

Caltrop can impact agriculture, recreation and urban areas. It competes with crops and pasture species, and its sharp burrs can injure livestock and contaminate wool or produce. The spiny fruits are also a nuisance to people and pets, puncturing bicycle and vehicle tyres. Burrs easily attach to shoes, clothing, tyres and animals, allowing the weed to spread quickly to new areas and can be costly to control. 

CONTROL OPTIONS

Caltrop is best controlled by preventing plants from producing burrs. Small infestations can be removed by hand pulling or hoeing young plants before seeds develop. For more well-established infestation herbicides can be used to control actively growing plants, and pre-emergent herbicides may be applied to the soil to prevent seeds from germinating.

Maintaining good ground cover and cleaning vehicles, machinery and footwear can help prevent the spread of burrs to new areas.

Permitted and on-label herbicides and rates can be found on the PIRSA Weed Control Website.

Declarations

Declared Plant Policy

Caltrop is declared under the following sections of the Landscape South Australia Act 2019:

  • 186(2) Prohibiting movement on public roads
  • 188(1) Prohibiting sale of the plant
  • 188(2) Prohibiting sale of contaminated goods
  • 192(2) Landowners to control the plant on their properties
  • 194 Recovery of control costs on adjoining road reserves

FURTHER INFORMATION

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