Wheel cactus (Opuntia robusta)

Also known as: Camuesa, cacti

Wheel cactus is an erect succulent plant with circular pads and yellow flowers. It forms dense thickets that restrict movement of people and animals.

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How does this weed affect you?

Wheel cactus forms dense thickets that outcompete low growing plants and prevent movement of animals and people. This means that:
• animals may not be able to access feed
• mustering is difficult
• access to watering points is reduced
• recreational activities such as bushwalking and camping are restricted.

Most plants have sharp spines that can:
• cause painful injuries to people, livestock, working dogs and pets
• injure and sometimes kill native wildlife that get trapped in the spines
• devalue wool and hides and prevent shearing
• get stuck around the mouth of lambs or calves and prevent them from feeding.

Wheel cactus competes with native plants, reducing food and habitat for native animals. 

What does it look like?

Wheel cactus is a succulent shrub usually 1–2 m tall. Sometimes it is treelike with a distinct trunk and up to 4 m tall. Cacti pads have bumps on the surface called areoles. Spines, bristles, leaves, flowers, fruit, roots and new shoots all grow out of the areoles.

Stems (also called pads or cladodes) are:

• bluish green
• fleshy
• circular and flat
• up to 40 cm in diameter but usually 20–25 cm
• covered in small raised bumps (areoles) that have hair-like bristles and spines.

Spines are:

• up to 5 cm long
• brown or yellowish at the base
• white near the tip
• in clusters of 1-12 per areole
• sometimes absent.

Flowers are:

• 5-8 cm in diameter
• yellow with reddish streaks on the underneath side of the petals
• often unisexual though sometimes one plant has three types of flowers: male, female and bisexual
• usually on the top section of the stems on both the edges and the faces.

Fruit are:

• pink, red or purple with dark red flesh
• round to oval 
• up to 8 cm long and 6 cm in diameter.

Seeds are:

• round
• 3-5 mm in diameter.

Roots are:

• shallow, usually in the top 15 cm of soil
• fibrous
• spread out over many metres.

Where is it found?

In NSW, most infestations are in the Western Region. There has been one infestation in the South East in the Snowy Mountains.

Wheel cactus is a native plant in Mexico. It was introduced into Australia as an ornamental plant.

What type of environment does it grow in?

Wheel cactus grows in a wide range of climates. It mostly grows in arid, semi-arid warm temperate and subtropical climates but it can tolerate cooler temperate areas.

It is very drought tolerant. Plants can survive extremely high temperatures up to 50 °C and low temperatures down to -7°C.

It tolerates a wide variety of soil types and grows very well in shallow granite soils.

Maps and records

• Recorded presence of Wheel cactus during property inspections (Map: Biosecurity Information System - Weeds, 2017-2023)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

By seed

Seeds are spread by birds (including emus), foxes and ants. Plants that grow from seeds do not produce fruit until they are at least 3 years old. Seeds are usually only dormant for one year.

Plant parts

New plants can grow from parts of the stem when they come in contact with the soil. Stem fragments can be spread by flood water and by people dumping garden waste.

References

Baker, J., Keller, M., & Preston, C. (2008). Genetic variability of wheel cactus (Opuntia robusta Wendl.) in southern Australia: implications for weed spread and biological control. In Proceedings of the 16th Australian Weeds Conference (pp. 18-22).

Del Castillo, R. F., & Argueta, S. T. (2009). Reproductive implications of combined and separate sexes in a trioecious population of Opuntia robusta (Cactaceae). American Journal of Botany, 96(6), 1148-1158.

Harvey, K.J., McConnachie, A.J. Sullivan, P. Holtkamp, R. & Officer, D. (2021). Biological control of weeds: a practitioner's guide for south east Australia. New South Wales Department of Primary Industries, Orange.

Nobel, P. S., & Zutta, B. R. (2008). Temperature tolerances for stems and roots of two cultivated cacti, Nopalea cochenillifera and Opuntia robusta: Acclimation, light, and drought. Journal of Arid Environments, 72(5), 633-642.

Parsons, W. T., & Cuthbertson, E. G. (2001). Noxious weeds of Australia. CSIRO publishing.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 14 April 2021 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Opuntia~robusta

Sheehan, M. R., & Potter, S. (2017). Managing Opuntioid Cacti in Australia: Best Practice Control Manual for Austrocylindropuntia, Cylindropuntia and Opuntia Species. Department of Primary Industries and Regional Development.

Snyman, H. A. (2006). Root distribution with changes in distance and depth of two-year-old cactus pears Opuntia ficus-indica and O. robusta plants. South African Journal of Botany, 72(3), 434-441.

More information

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Control

Successful weed control relies follow up after the initial efforts. This means looking for and killing regrowth or new seedlings. Using a combination of control methods is usually more successful.

Prevention

Act early by removing any individual plants before they spread.

Do not grow wheel cactus in gardens or pots. Do not take cuttings of unknown cactus plants to grow out or share with others. 

Avoid driving through areas with cacti. If you have been in an area with cacti check under vehicles, caravans, and machinery before leaving the infested area. Remove all plant parts using pliers or tongs. Dispose of them appropriately.

Physical control

Dig up small or isolated plants using a mattock or other tools. Wear appropriate protective clothing and gloves to protect against injuries from the spines and bristles. 

Larger infestations may be controlled by machinery. Ensure the roots are dug out and that all plant parts are disposed of.

Disposal

Dispose of wheel cactus by burying it at least one metre deep or by burning in a hot fire. Check disposal sites regularly and control any seedlings. Contact your local council for information about other disposal options. 

Biological control

Two types of cochineal insect can effectively control large, dense infestations of wheel cactus: 

• Dactylopius opuntiae ‘ficus' lineage 
• Dactylopius opuntiae ‘Mexican' lineage.

Control will take several years. Biological control is suitable for areas that are environmentally sensitive, too difficult to access or where other methods would be too expensive. Cochineal insects are less effective on scattered infestations and may require redistribution at these sites.

There are several species of cochineal that look very similar. It is important to use the correct species of cochineal for each species of cactus. Contact your local council weeds officer for information about using cochineal to control wheel cactus.

The cactoblastis moth Cactoblastis cactorum attacks wheel cactus but only provides limited control.

Chemical control

Herbicides are especially useful for sparse, scattered infestations. 

Spot spraying

Spray when plants are actively growing. Thoroughly cover all parts of the plants with herbicide mix. Plants may regrow after spraying and follow up applications may be required.

Injection

Wear the appropriate personal protective clothing described on the herbicide label. Drill into the base of the stump with a long bit on a battery drill to avoid thorns and inject with a handheld injection gun and forestry spear.

Herbicide options

See Using herbicides for more information.

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Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon Extra®)
Rate: 500 mL per 100 L of water
Comments: Follow the label instructions as per Prickly pear (common). Spray actively growing plants. Thoroughly cover all of the plant with herbicide mix to the point of runoff. Regrowth may occur, so a follow-up application may be necessary. To improve uptake add a paraffinic oil e.g. Uptake®, Titan Paraffin or Apparent Paraffinic spraying oil at the rate of 500 mL per 100 L of water.
Withholding period: Where product is used to control woody weeds in pastures there is a restriction of 12 weeks for use of treated pastures for making hay and silage; using hay or other plant material for compost, mulch or mushroom substrate; or using animal waste from animals grazing on treated pastures for compost, mulching, or spreading on pasture/crops.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Triclopyr 300 g/L + Picloram 100 g/L (Various products)
Rate: 500 mL per 100 L of water
Comments: Spray actively growing plants. Follow the label instructions as per prickly pear common. To improve uptake of add a paraffinic oil e.g. Uptake®, Titan Paraffin or Apparent Paraffinic spraying oil at the rate of 500 mL per 100 L of water.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Triclopyr 600 g/L (Garlon® 600)
Rate: 1 L in 75 L of diesel.
Comments: Follow the label instructions as per common prickly pear (Opuntia spp.). Spray actively growing plants. Thoroughly cover all of the plant.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Triclopyr 600 g/L (Garlon® 600)
Rate: 3 L per 100 L of water
Comments: Follow the label instructions as per common prickly pear (Opuntia spp.). Spray actively growing plants. Thoroughly cover all of the plant to the point of runoff. To improve uptake add a paraffinic oil e.g. Uptake®, Titan Paraffin or Apparent Paraffinic spraying oil at the rate of 500 mL per 100 L of water.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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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 pest 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	Prohibition on certain dealings Must not be imported into the state, sold, bartered, exchanged or offered for sale.
Central Tablelands	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
Central West	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
Hunter	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
Murray	Regional Recommended Measure* (for Regional Priority - Containment) Whole of region: Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
Western	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land A person should not buy, sell, move, carry, or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
	*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here

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Reviewed 2023