Kangaroo Island
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Khaki weed (Alternanthera pungens)

Khaki weed (Alternanthera pungens)

Medium Risk Weed for Kangaroo Island

Khaki weed 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

Khaki weed is native to Central and South America and is a declared weed in South Australia. It is a low growing plant that forms dense mats and produces sharp, spiny burrs. It spreads easily by sticking to shoes, animals and vehicles. Infestations can reduce pasture quality, suppress native plants, and cause injuries to people, pets, and livestock.

Khaki weed is a declared pest plant in South Australia under the Landscape South Australia Act 2019 and requires notification of presence on Kangaroo Island.

It is a summer growing perennial plant that prefers light soil, warm conditions and high soil moisture over spring and summer. It grows rapidly in irrigated pastures and crops. Infestations mostly occur where vehicles traverse and stock compound soil.

There have been several infestations of khaki weed on Kangaroo Island with the most recent ongoing one at Reeves Point on the outskirts of Kingscote.

You can help keep Kangaroo Island free of Khaki weed by:

  • Learning to recognise caltrop plants and burrs.
  • Cleaning out the footwell of your vehicle before travelling to Kangaroo Island.
  • Requesting a vendor declaration when purchasing farm produce or stock feed.
  • Reporting any suspected plants to the Kangaroo Island Landscape Board.
Khaki weed (Alternanthera pungens)

DESCRIPTION

  • Growth form: low-growing, prostrate perennial woody taproot forming dense mats in summer; stems root at the nodes.
  • Leaves: small, oval to oblong, green, arranged opposite along the stems; smooth edges.
  • Flowers: tiny, yellow, often partially hidden among the leaves; appear mainly in summer.
  • Fruit: hard, spiny burrs (up to several thousand per plant) that easily stick to shoes, animals, and equipment.
  • Seed: one or two seeds per burr; seeds are dispersed by attachment to animals, humans, vehicles, or soil movement and remain viable in the soil seed bank up to 5 to 6 years.

IMPACTS

Khaki weed mainly impacts lawns, parks, sports fields, and other recreational areas, crowding out desirable grasses and small plants. Its sharp, spiny burrs can injure people, pets, and children, making these areas unpleasant and potentially hazardous to use. It can also crowd out native plants and reduce pasture quality. Its sharp, spiny burrs can also injure stock.

CONTROL OPTIONS

Khaki weed is best controlled by preventing plants from producing burrs. Small infestations can be removed by hand pulling or hoeing young plants to remove the taproot 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 covers 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

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

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

FURTHER INFORMATION

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