Quick Facts

Quick facts

  • Originally from the Americas, Prickly Pears (Opuntia species), Weeds of National Significance, are succulent drought tolerant shrubs or small trees with cylindrical or flattened stems armed spines impacts on the environment, agriculture and the economy across Australia especially in arid to semi-arid areas
  • Armed with sharp large spines and detachable small glochids (bristle like or hair like spines with reverse barbs), both can penetrate skin causing irritation and occasionally lead to infection of wounds.
  • They form dense impenetrable patches that can cause injury to wild animals and livestock, and harbour pest species and reduce land productivity.
  • All are spread vegetatively with many species also spread by seed, invading most habitats if allowed to establish.
  • Physical removal of plants appears to be the most effective control method, but spines and glochids, asexual reproduction from stem segments, and long distance dispersal of seeds by animals makes controlling populations difficult.
  • Biological control agents are useful for controlling some species but not others, and their effects are limited in cooler climates.

What Does It Look Like?

What is it?

Prickly Pears belong to the genus Opuntia, and most species are considered weeds or potential weeds in most states of Australia. These species are shrubs or small trees to 10 m with jointed, succulent stems (pads or cladodes), normally flattened, cylindrical, club-shaped, or compressed. Leaves may be produced on new growth but are not usually retained, mostly scale-like, or linear, or narrow in shape, and usually tapering gradually to a fine point. The areoles (spots on the stem segments) are tufted with many hair-like barbed bristles (glochids) and with spines, usually 1 or more, rarely absent. The stout spines are barbed or smooth, lacking a spine sheath.

The flowers are usually solitary and stalkless (sessile), are produced on the areoles. Flowers are typically showy and large, generally bisexual (with both male and female reproductive structures), rarely uni-sexual. The colourful petals are in fact 'tepals'. Tepals are either sepals or petals that are all petal -like and similar in appearance, rather than conventionally remaining as defined structure with 'sepals normally the outer whorls of a flower and are usually green, and the petals normally the inner whorl of a flower that are usually soft and coloured conspicuously. The colourful 'tepals' are collectively called a perianth. The flowers of Opuntia species found in Australia vary in colour ranging from yellow, orange, red to purple, with numerous stamens (male reproductive structures).

The fruits are dry or juicy, remain attached to the plant pads (indehiscent), often with many fruit and sometimes, producing chains, all with glochidiate areoles like the plant pads, and sometimes with spines. The seeds are few to many in each fruit, white to brown, compressed, generally circular (disc-shaped or discoid) or irregularly shaped (Telford 1984; Aluka 2008) to kidney shaped.

Individual weed profiles for Tiger Pear (Opuntia aurantiaca), Prickly Pear Cactus (Opuntia monacantha), Wheel Cactus (Opuntia robusta), White-spined Prickly Pear (Opuntia streptacantha), Common Prickly Pear (Opuntia stricta), and Velvet Prickly-pear (Opuntia tomentosa) are also available on this web site.

For further information and assistance with identification of Prickly Pears, contact the herbarium in your state or territory.

Flower colour

Yellow, Orange, Purple, Red

Growth form (weed type/habit)

Tree, Shrub

Where it currently grows? Preferred habitat

Prickly Pears are native to tropical and temperate regions in North and South America and the Galapagos Islands. In Australia, a number of species are naturalised in sub-humid, semi-arid and arid areas in sub-tropical, tropical and warm temperate regions (Telford 1984; Parsons & Cuthbertson 2001) and cool temperate areas. All Opuntia species are drought resistant as their reduced leaves and succulent stems minimise water loss (Parsons & Cuthbertson 2001).

Are there similar species?

Opuntia is readily distinguished from other cacti by the presence of clusters of detachable bristles (glochids) in the areole (spots on the stem segments) (R. Chinnock, pers. comm.).

Why Is It A Weed?

What are its impacts?

Prickly Pears (Opuntia) can form dense patches that are virtually impenetrable to people and most animals and can harbour pest species. Opuntia species can have serious impacts on agriculture, the environment, and aesthetically posing a risk to human and animal welfare and safety (Sheehan & Potter 2017).

Agriculture: Prickly Pears can form dense patches that are virtually impenetrable to stock and other animals, and can harbour pest species such as rabbits. Furthermore, the fruits of some species can harbour fruit fly which can be difficult to eradicate without destroying all the fruits within a population. These species are not readily grazed due to their stout spines, and these can cause injury to animals and humans as they readily pierce the skin, cause irritation, and glochids can be difficult to remove. Where they occur in dense patches on cultivated land they can significantly reduce land productivity (Parsons & Cuthbertson 2001).

Native ecosystems:  Although scattered plants have little effect on native ecosystems, dense infestations can affect biodiversity by hindering the growth and regeneration of native plants, particularly small shrubs and ground-flora (Muyt 2001).

Urban areas: Plants can take over in neglected or abandoned areas, and can further spread to similar areas, roads verges and reserves, in towns and cities in arid to temperate areas.

Health and safety concerns: Plants can cause serious injury to humans and domestic pets. Physical injury associated with Opuntia species is from the spines and glochids. These are borne on the areoles on pads and flowering and fruiting body (Chinnock 2015). The large spines can can inflict considerable injury, penetrating skin requiring careful removal to avoid further damage. Removal of spines can result in bleeding followed by bruising, and in rare cases serious infection, and in extreme cases death can occur (Chinnock 2015). Glochids are small hair-like sharp detachable spines with reverse barbs produced in dense cluster on the areoles. These small glochids penetrate and irritate skin, and are barely visible to impossible to see with out the aid of a hand-lens. These features create difficulties when trying to identify the remove glochids from affected skin. Even glochids detached from plant on equipment, surfaces or clothes can also penetrate skin if brushed past.

For further information on impacts and safety and wellbeing see, 'Managing Opuntioid Cacti in Australia; Best practice control manual for Austrocylindropuntia, Cylindropuntia and Opuntia species' at: https://www.agric.wa.gov.au/sites/gateway/files/Opuntioid%20cacti%20best%20practice%20control%20manual.pdf

How does it spread?

Many Prickly Pears reproduce asexually from stem fragments, flowers or immature fruits. These produce roots when they come into contact with the soil. Roots are produced from areoles on the underside and new stems are produces from aroeles on the upper surface (Chinnock 2015).

Local dispersal can occur through stem fragments and fruit dropping to the ground and producing new plants. Plant fragments can also be dispersed in flood waters or by native animals and stock when the spines attach to fur and segments are transported to new areas.

As many species are used as ornamentals and hedge-plants, they have been spread by people dumping plant parts in rubbish tips or waste areas, which is a major cause of spread of these species in Australia.

The fleshy fruit are also attractive to birds and animals, which can disperse the seeds (Parsons & Cuthbertson 2001).

What is its history in Australia?

A number of Prickly Pear species were brought to Australia on the First Fleet with the intention of establishing a cochineal industry as these species are hosts for the cochineal insects. Other Opuntia species are widely cultivated as ornamental plants, hedge plants, or as food plants (Telford 1984) and have been introduced via this method and escaped cultivation. Opuntia ficus-indica iis grown commercially in Australia for its edible fruit (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

When controlling Opuntia Prickly Pear species, an integrated weed management approach is usually desirable especially for larger infestations.

Chemical control: While several herbicides are recommended for managing Prickly Pears, chemical control is not always effective, as many species occur on rocky slopes, and infested areas must be checked and resprayed over several years if necessary (Parsons & Cuthbertson 2001). Methods used are:

  • Foliar spray covering all pads
  • Stem injection (includes drill and fill method on every 2-3 pads)
  • Basal bark and cut stump (not normally used or considered best practice).

However, plants are extremely hardy and follow up and monitoring may be required for 1-2 years to ensure plant do not re-sprout. Registered herbicides,  techniques and on-label instruction should always be followed in your state or territory. A variety of herbicides (chemicals) are know to be effective. Please see Sheehan & Potter (2017) for an overview. Also see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au. Permits from state or territory Environment Protection Authorities may be required if herbicides are to be sprayed on riverbanks.

Non-chemical control: Physical control: Physical control either by manual (hand) or mechanical (machine) removal can be feasible and cost-effective for all species of Opuntia (Prickly Pears).

Manual (hand) removal appears to be one of the most effective control methods for for scattered and small infestations (Sheehan & Potter 2017). However, the spines make manual removal of these species difficult (Parsons & Cuthbertson 2001). Using tools and avoiding spines and glochids is a top health and safety concern when working with Prickly Pears. Personal Protective Equipment (PPE) must (should) be worn, and tools used that eliminate or significantly reducing handling of plants with spines and glochids used.

Mechanical (machine removal) is useful for large dense impenetrable stands (Sheehan & Potter 2017). This method is useful for removing bio-mass and increases accessibility for other follow-up control methods. Machine removal with front end loaders causes high levels of disturbance and will require planning and long term follow-up using an integrated weed management techniques for cacti and other weeds that could colonise the area. Normally mechanical control should be carried out when conditions are dry to avoid damaging soil reducing soil disturbance, reducing likely spread of plants. However caution should be employed as some species have glochids that are airborne and are more likely to dislodges and injure workers with PPE like masks or respirators worn with eye protection

Disposal: Care must also be taken to remove and properly dispose of plants parts. Pads, flowers, fruits and even small sections of stems if left on the soil surface can produce roots and grow into a new plant. If one larges plant is uprooted, broken up, and left on the soil surface, each pad will take root and form a new plant. Where one plant was present there would now be many plants. The root system must also be dug out to prevent regrowth (Parsons & Cuthbertson 2001). Plant can be buried at a depth of 1 metre on or off site. Burning plants (all vegetative, flowering and fruiting parts) with other dry materials for plants thahave dried out over summer can also be used to kill plants. However, you should consult you local fire service for advice and permissions.

Fire: The effect of fire on Prickly Pears are not well understood. For some species it has been shown that fire is not effective in killing all plants and they can recover with great vigour. In addition, fire and strong winds are thought to spread the stem segments of some species aiding spread (Sheehan & Potter 2017).

Biological control: Biological control using Cactoblastis moths or Cochineal insects can be effective on dense populations, and outlying plants can be infected by transferring infected pads to them (Parsons & Cuthbertson 2001). However, there are a number of species of Cochineal insects that are host specific, and may destroy one species of Opuntia but not others (R. Chinnock, pers. comm.). The effect of these agents appears to be limited in colder climates (Muyt 2001).  Correct identification of Opuntia species is required so the host specific biological control can be used. Further information can be found in Sheehan & Potter (2017).

Does it have a biological control agent?

YES. Twenty species of biocontrol agents have been released against prickly pears. Ongoing work to identify which cochineal agents can be utilised against previously untested Opuntia species and how biocontrol can be optimised through integrated weed management practices (Harvey,  et al 2023).

When does it grow? (lifecycle/growth calendar)

All Prickly Pears reproduce from broken-off stem segments which develop roots from lower areoles (spots on the stem segments) that are in contact with the soil surface. Detached plant parts from some species have been known to last up to 3 years indoors.

Most Prickly Pears that occur in Australia can also reproduce by seed. Seeds germinate any time of year and plants generally flower at three years old. All Prickly Pears are long lived (Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?

Found in all states and territories

What areas within states and territories is it found?

Prickly Pears are widespread in Australia, with one or more species occurring in all states and territories. At least 20 species have been recorded as more or less naturalised (Telford 1984).

Where does it originate?

Prickly Pears occur naturally throughout North and South America (Telford 1984).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

YES (except Opuntia ficus-indica)

Where is it a declared weed?

ACT, NSW, SA, TAS, VIC

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Opuntia spp.

Other scientific names (synonyms)?

 

M.R. Sheehan and S. Potter. Western Australian Agriculture Authority (Department of Primary Industries and Regional Development), 2017.

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