Opuntioid Cacti

Austrocylindropuntia spp., Cylindropuntia spp., and Opuntia spp. (excluding Opuntia ficus-indica)
(Opuntia spp. includes prickly pear, O. stricta)

    
Image: Opuntia robusta tree,
Mt Archer National Park, Q'ld,
showing the flat, pad-like segments,
© Mark Marathon (Wikimedia).

What are Opuntioid cacti?

  • Opuntioid cacti are a group of perennial plants that belong to a sub-family of Cactaceae. There are three genera, (and approximately 30 species), of Opuntioid cacti that have naturalised in Australia: Austrocylindropuntia, Cylindropuntia and Opuntia; varying degrees of infestations are known to be in all states and territories, (except the Australian Capital Territory).
  • Opuntioid cacti Austrocylindropuntia spp., Cylindropuntia spp., and Opuntia spp. (excluding Opuntia ficus-indica), are declared weeds under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of these Opuntioid cacti are prohibited in Tasmania.
  • These Opuntioid cacti are also Weeds of National Significance (WONS).
  • Opuntia spp., (excluding Opuntia ficus-indica), is known to have limited populations in Tasmania.

How to identify Opuntioid cacti

  • The appearance of Opuntioid cacti can vary significantly, from the more familiar tall, erect and flat segmented common prickly pear (O. stricta), through to small shrubs with narrow, flattened, rope-like segments such as Hudson pear (C. rosea, C. tunicata).
  • Austrocylindropuntia originate in South America and have a shrubby, tree-like habit with cylindrical to club-shaped segments, each up to 50cm long. They differ from Cylindropuntia species in that their spines lack papery sheaths. Of the 11 species worldwide, two have naturalised in Australia: A. cylindrica and A. subulata.

    Austrocylindropuntia cylindrica
    have pink-red flowers,
    © John Rusk (Wikimedia).

  • Cylindropuntia are native to south western USA, Mexico and the West Indies. The 1-4cm long spines of Cylindropuntia species, such as Hudson pear (C. rosea), are contained within papery sheaths for the first year and can give the plant a silver or gold appearance. Spines are 1-4 cm long. Many species have easily detachable segments, such as C. prolifera.

    Many Opuntioid cacti
    are covered in spines,
    © Steve Koch (Wikimedia).

  • Opuntia originate in North America, the West Indies and South America. They are branched shrubs, typically up to two metres high, though they can grow taller. They have flattened stem segments, commonly referred to as pads, which are usually round or oval shaped. The most well known Opuntia species is common prickly pear, introduced to Australia in the 19th century.

    Prickly pear infestation,
    © Q'ld Gov’t.

  • Dense infestations of Opuntioid cacti compete with native vegetation, limiting the growth of small shrubs and groundcover species. The plant’s sharp spines or barbs can cause injury to stock and native animals and contaminate wool and hides, reducing or preventing grazing activities and productivity.
  • Flowering typically occurs from spring through to summer, with fruits forming in late summer and into autumn. Not all species develop mature fruit or viable seeds, but those that do can produce numerous seeds, with a hard seed coat enabling longevity. The spread of cacti is aided by the movement of water, hence distribution often occurs along watercourses, drainage lines and across flood plains.
  • Native to the Americas, some species of these generally long lived cacti were introduced into Australia to support cochineal dye production, while others were planted as garden ornamentals or hedges.
  • One of the most well-known opuntioid cacti is common prickly pear (O. stricta), which covered some 240 000 km2 of the Australian Mainland before the introduction of the Cactoblastis moth, a highly successful biological control agent, in 1926.
  • Most spread in Australia has been by people, either as garden plants and hedges, or through dumping in rubbish tips or bushland.
  • For further information or help in identifying Opuntioid cacti, refer to the Weed Management Guide (Weed of National Significance) - Opuntioid cacti, published by the Commonwealth of Australia. If you are still in doubt about the weed you are dealing with, contact Biosecurity Tasmania on 03 6165 3777 for help.

Opuntioid cacti in Tasmania

  • Limited populations of Opuntia spp., (excluding Opuntia ficus-indica), are currently known to be present in Tasmania.

Legal status of Opuntioid cacti in your area?

  • The legal responsibilities of landholders and other stakeholders in dealing with Opuntioid cacti are laid out in the Statutory Weed Management Plan for Opuntioid cacti.
  • For details regarding distribution of Opuntioid cacti, including whether your area falls in an eradication (‘Zone A’ municipality), or containment (‘Zone B’ municipality), refer to the Tables and information provided in Section 12, ‘Management of Opuntioid cacti by municipality’, in the Statutory Weed Management Plan for Opuntioid cacti.

See Also
Herbicides for Opuntioid Cacti Control
Statutory Weed Management Plan for Opuntioid cacti
Useful Weed Resources

Other useful links
Weed Management Guide (Weed of National Significance) - Opuntioid cacti
Pest Genie
APVMA

Opuntioid Cacti Control Guide

Do

  • Plan your control program, this will save time and money in the long-run;
  • Consider the impact of your control methods on off-target species, especially if herbicides are used;
  • Ensure machinery and equipment is washed down between sites or prior to contractors leaving site;
  • Get in early - for new infestations, eradicate before the plants reach the flowering stage: once plants begin seeding, control becomes more difficult and expensive;
  • Carefully time your use of herbicide for best results (see Herbicides for Opuntioid cacti Control for more information);
  • Coordinate your control program with neighbouring landholders where your weed problem crosses property boundaries;
  • Revisit and regularly inspect the site and ensure follow-up is undertaken;
  • Use a combination of different control methods; and
  • To reduce re-infestation, restore the disturbed habitat with new plants such as native species, non-invasive garden species, vigorous pasture and/or production crops where suitable.

Don't

  • Don't introduce Opuntioid cacti to Opuntioid cacti-free areas (e.g. by failing to wash down machinery and equipment between sites);
  • Don't start your control program without first planning your approach;
  • Don't allow Opuntioid cacti to flower and set seed before treatment;
  • Don't rely on one attempt at removal - follow-up is essential;
  • Don't rely on just one control method;
  • Never burn Opuntioid cacti without follow up treatment of regrowth; and
  • Do not burn Opuntioid cacti in native vegetation.

Spread of Opuntioid cacti

  • Vegetative spread is the most common form of dispersal, occurring year round when stem fragments, immature fruit or flowers detach and make ground contact. New segments then grow from areoles on the upper surface of the segment.
  • Segments of many opuntioids will attach easily to clothing, footwear and the fur and limbs of animals, further aiding their spread.
  • Long distance dispersal can also occur on vehicles and machinery.
  • Most spread in Australia has been by people, either as garden plants and hedges, or through dumping in rubbish tips or bushland.
  • Seeds are a less common form of spread as not all Opuntioid cacti produce viable seed. Species such as wheel cactus (O. robusta) and common prickly pear (O. stricta) produce bright, large fruit that are attractive to birds and some animals, aiding dispersal by passing through in a viable condition in the droppings.
  • The spread of Opuntioid cacti is also aided by the movement of water; hence distribution often occurs along watercourses, drainage lines and across flood plains.

Successful control strategies

  • Good hygiene is essential when working in infested areas, including staying on tracks. All segments and fruits should be removed from an area as they are capable of re-growing, even under very harsh conditions.
  • Consider the topography of the land; as gravity and surface water movement can spread segments and seeds from ridgelines down gullies and along water courses, any infestations on high ground or at the top of frequently flooding catchments should be prioritised.
  • While there are several options for managing Opuntioid cacti, the most appropriate method will depend on the size and age of the infestation, site access, resources and the species being managed.
  • For large infestations, integrated weed management approaches will be necessary, using a combination of biological control (if available), herbicides and or/manual removal.
  • Ensure all equipment is cleaned and checked for any adhering Opuntioid cacti segments before moving to un-infested areas.
  • Follow-up is essential in any control program, particularly given the ability of cacti to readily reproduce from segments or fruit.

Physical removal / Mechanical control

  • Physical removal and burning in wood fire heaps, together with cultivation and removal of the root system, can be used for small accessible infestations of Opuntioid cacti.
  • Small quantities of collected material may be killed by deep freezing at -20oC for 48 hours.
  • Care must be taken when mechanically or physically removing Opuntioid cacti due to their spiny nature.
  • Small, isolated plants are easier to remove than large, dense infestations and some species, (such as Hudson pear and devil’s rope), can pose significant risk of injury when handled.
  • Physical removal can be difficult as any segments detached in the process can regrow to form new plants. Remove, collect and bury all fragments, as any that are left or dropped during transport to the burial site will regrow.
  • Material must be disposed of appropriately via deep burial under 1m of topsoil.

Fire

  • Hot fires can kill plants, although regrowth may occur.
  • Burning can also assist in providing access to sites so that other control activities can take place, and help remove the bulk of the plant to reduce the amount of herbicide required for follow up control.
  • Note: Great care is needed when using fire. Appropriate conditions, equipment and experienced personnel are essential. The landowner is responsible for ensuring that all planned burning can be contained and is conducted in a safe manner. Prior to any planned burn being undertaken, the landowner must inform all relevant authorities and obtain all relevant permits. The Tasmania Fire Service is the responsible authority for granting fire-permits.

Grazing

  • The spines on Opuntioid cacti prevent grazing in most instances, however, stock and other animals sometimes feed on less spiny species in times of drought. In most instances the presence of Opuntioid cacti limits or prevents grazing activities.

Biological control

  • Biological control is the use of a living species, usually an insect, mite or disease, to control a weed.
  • Biological control will not eradicate an unwanted plant species, but may be used in conjunction with other control methods.
  • Perhaps the most well-known Opuntioid cacti is common prickly pear (O. stricta), which covered some 240 000 km2 of New South Wales and Queensland before the introduction in 1926 of the stem-boring moth Cactoblastis cactorum, and several Dactylopius species, (cochineal scale insects).
  • Cactoblastis has been an extremely successful biological control agent, controlling common prickly pear in most situations, although it is less effective in cooler, wetter areas or very dry locations.
  • Successful control was achieved by 1935.
  • For more information on biological control programs in Tasmania contact the Tasmanian Institute of Agriculture.

Chemical control

  • The Australian Pesticides and Veterinary Medicines Authority (APVMA) regulates the use of chemicals in Australia. In some instances off-label permits are issued by the APVMA, to allow for uses that are not specified on the label. There are four off-label permits for the control of opuntioid cacti in SA, NSW and Queensland. For more details on herbicide registration and permits visit the APVMA website, www.apvma.gov.au.
  • Registration of herbicides varies across states and territories. You should always check the product label and seek advice from your local council or state/territory weed management agency* for information on spray rates and adjuvants.
  • Herbicides for Opuntioid Cacti Control provides a summary of the registered or permit herbicide options available for the control of opuntioid cacti in Australia.
  • High levels of control may be achieved by drilling a 1cm hole about 10cm deep into the base of the major stems and filling it with an approved herbicide*. Space the holes about 20cm apart on large plants. A cordless drill with a 75cm long bit and a converted drench gun with a 75cm long probe is often used to reduce the risk of operator injury from the spines.
  • Opuntia species respond well to stem/ pad injection, while many Cylindropuntia species require overall spraying. When using herbicides, care must be taken to ensure adequate coverage of the plant, (all sides of the segments), to prevent re-growth.
  • In the case of foliar spraying, the addition of a marker dye will assist with identifying any missed plants or segments.
  • Plants should be actively growing and not under stress from heat/drought or cold conditions. Plants may die quicker as a result of warm weather spraying, as cooler conditions can slow the uptake of herbicides.
  • Herbicides may not result in a complete kill. Control sites should therefore be monitored for regrowth and follow-up activities applied if necessary.
  • Application of herbicides must be done with extreme care, following label or permit instructions and by an experienced operator.
  • If you have any questions about herbicide control of Opuntioid cacti, contact Biosecurity Tasmania on 03 6165 3777 for help.

Herbicides for Opuntioid Cacti Control

Herbicides for Opuntioid Cacti Control


Important Disclaimer
To the extent permitted by law, the Tasmanian Department of Primary Industries, Parks, Water and Environment (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using information or material (in part or in whole) contained on this website.

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