Prickly Pear

Opuntioid cacti

Prickly Pear

Image credit: Bob Chinnock, State Herbarium of SA

Plants in the Prickly Pear group of cactuses (Opuntioideae) are highly invasive succulent shrubs that degrade native vegetation and pasture. 

In South Australia all but one cacti in the Opuntioideae are declared pests under the Natural Resources Management Act 2004 (NRM Act).

Opuntia ficus-indica is cultivated as a commercial and ornamental plant and is excluded from the declaration.

Description

  • sprawling, generally leafless plants, with large fleshy stem segments armed with 1–4 cm long spines
  • not usually grazed by stock because of the stout spines
  • all species are drought tolerant
  • propagate by clonal growth, by seed and by broken stem segments
  • segments of several species can attach to passing animals
  • segments can take root and form new plants where they touch the ground
  • detached segments can remain dormant for several years before forming a new plant.

There are three genera in the opuntioid group:

1. Austrocylindropuntia 

  • large succulent shrubs with cylindrical to club-shaped segments
  • there are 11 species in this genus of which two are naturalised in Australia
  • flowers are scarlet to orange.

2. Opuntia

  • branching shrubs that grow to about 2 m high
  • some tree varieties grow to 8 m including Opuntia tomentosa and O. monocantha
  • they have flattened stem segments called pads that are usually round or oval shaped
  • flowers are yellow to orange.

3. Cylindropuntia

  • commonly called Rope Cactus
  • a shrubby or tree-like form with cylindrical (rope-like) branching segments.

Impacts

  • pests of neglected and poorly managed pastures
  • dense infestations displace pasture plants and can restrict stock movement
  • spines can injure stock and affect the safe handling of animals, particularly for shearing
  • significant environmental weeds, particularly in grasslands, grassy woodlands and coastal areas
  • infestations compete with native shrubs and groundcover species
  • a hazard to wildlife, either through impalement or the lodgement of spiny segments in limbs, hides and mouths, leading to immobilisation and a painful death
  • dense infestations provide shelter for pest animals such as foxes and rabbits
  • Opuntia species are hosts of fruit-fly.

Distribution

  • native to North America, the West Indies and South America
  • approximately 27 species are naturalised in Australia
  • hotter, northern, low-rainfall regions of the Mount Lofty Ranges are most vulnerable
  • widespread on roadsides and in watercourses where propagules are readily spread by water
  • expanding in poorly managed pastures and disused orchards
  • present, but generally less abundant, in the wetter and cooler parts of the southern Mount Lofty Ranges
  • an exception is the Willunga Basin where infestations are extensive
  • Onkaparinga Gorge has the second largest infestation in the state
  • several species are present in the Onkaparinga Gorge and on the Gawler River
  • local dispersal around existing clumps occurs when segments or fruit drop to the ground and take root
  • fragments are readily dispersed by animals, vehicles, footwear, along watercourses and in flood water
  • several species produce viable seed in bright, edible fruit that are consumed by emus and other birds, as well as foxes, cattle, goats and sheep.

How to control this weed

  • readily controlled by herbicide applied by spray or injection 
  • two biological control agents, a moth and a scale insect, have been effective in reducing the abundance of Prickly Pear (Opuntia stricta)
  • the Cochineal scale insect is the primary tool for controlling most Opuntioid cacti at the landscape scale
  • for advice on chemical control techniques contact your nearest Natural Resources Centre
  • refer to the 'Weed control handbook for declared plants in South Australia' for advice on chemical control. You can find it on the Biosecurity SA website.

Declarations

The following sections of the NRM Act apply to Opuntioid cacti in the Adelaide and Mount Lofty Ranges region:

  • 175 (1) Cannot import the plant into South Australia
  • 175 (2) Cannot transport the plant, or any material or equipment containing that plant, on a public road
  • 177 (1) Cannot sell the plant
  • 177 (2) Cannot sell any produce / goods carrying the plant
  • 182 (2) Landowner must control the plant on their land
  • 185 (1) NRM authority may recover costs for control of weeds on roadsides from adjoining landowners

More information

For more detailed information download the fact sheet.

Please contact us for advice and assistance with controlling Prickly Pear.

Natural Resources Adelaide and Mount Lofty Ranges