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Opuntia stricta

Description
 

Common Prickly Pear is an erect spreading shrub usually 0.5-1 m tall (occasionally to 2 m) and 0.5-5 m across. The stem segments at the base often thicken and form a trunk. The flattened stem segments (pads) are elliptic to egg-shaped, 10-30 cm long, 5-20 cm broad and 1-2 cm thick. They are dull green to grey-green with a whitish waxy bloom. The areoles (spots on stem segments and fruits that contain the spines and glochids) are scattered and may be spineless or bear 1-11 spines 1-6 cm long and numerous short glochids (barbed bristles). The leaves are very small and drop off. The flowers are 5-8 cm diameter, the petaloid lobes are yellow but the outer smaller ones are often greenish to pinkish. The almost rounded to pear-shaped fruits have scattered prominent tufts of glochids. They are succulent and purple with a white waxy bloom at maturity, 4-8 cm long and 2.5-4 cm in diameter. Seeds are numerous, yellow to pale brown, 4-5 mm across (Stanley & Ross 1983; Telford 1984; Anderson 2001; Harden 1990).

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

Distribution:

Common Prickly Pear is extremely widespread throughout the eastern areas of Australia and it is also scattered throughout many other parts of the country. It is most abundant in central and southern Queensland and in northern New South Wales and relatively common in the rest of New South Wales. It is common in northern and western Victoria, and from the Flinders Ranges south to the Murray Region in South Australia. It also occurs in the western and south-western regions of Western Australia and in scattered locations in northern Queensland and in the southern part of the Northern Territory (Navie 2004).

Habit:Shrub
Key points:
  • Common Prickly Pear (Opuntia stricta) is an aggressive invasive weed that can take over pastoral and agricultural lands.
  • Historically, common Prickly Pear was a catastrophic weed of parts of Queensland and New South Wales until the introduction of the cactoblastis moth.
  • Stem segments fragment and can be distributed by animals, vehicles and by water or wind.
  • Fruits are succulent and are eaten by birds and animals and seed is distributed in their droppings.
  • It can cause injury to people and animals.
  • If this species is seen please notify your local weed management authority.
How it spreads:

Common Prickly Pear readily reproduces from stem fragments, fallen flowers or immature fruits which easily break of and readily root within a few months or from seed. The succulent fruits are attractive to birds and animals (e.g. foxes) and the seeds are carried in their droppings. Plants growing adjacent to creeks and waterways can be dispersed readily downstream and much further during floods. Discarded plants and movement of plant parts during disposal has led to new outbreaks (Navie 2004).

Where it grows:

Common Prickly Pear is widespread, common to abundant invading mallee and acacia woodlands, open shrub lands, pastoral areas and agricultural lands and disturbed areas. It grows on plains, ranges, rocky steep slopes, beaches and off-shore islands on a great variety of soil types including heavy clays, loams, saline soils and sands (Chinnock 2007, pers. comm.).

Flower colour:Yellow
Distribution map:

http://www.weeds.org.au/cgi-bin/weedident.cgi?tpl=plant.tpl&state=&s=&ibra=all&card=S12 

Impacts:

Common Prickly Pear is an aggressive drought tolerant weed that is easily dispersed by fragmentation. Dense infestations can impede movement of stock, lay waste to agricultural and pastoral lands By 1926 half of the area infested with Common Prickly Pear was so densely covered that it could no longer be used for grazing or agriculture (Parsons & Cuthbertson 2001; Chinnock 2007, pers. comm.).

It can harbour pests such as rabbits. Spines and glochids can cause injury to humans and animals. The fruits are hosts to fruit fly (Parsons & Cuthbertson 2001; Land Protection 2006b).

Stock does not usually graze on common Prickly Pear due to the presence of the spines and bristles which can damage their mouths. However, in times of drought plants are eaten which may have contributed to its spread during the drought of 1902 (Parsons & Cuthbertson 2001).

Prickly Pears can dominate the vegetation of rocky outcrops displacing natives, some of which may be restricted to such outcrops, and consequently be relatively rare (GISD 2005).

Origin:

Common Prickly Pear is native from the southern United States south to Mexico, Caribbean and Ecuador (Anderson 2001).

History:

The first introduction of common Prickly Pear is thought to have been by Governor Phillip at Port Jackson in 1788 along with drooping Prickly Pear and possibly a couple of other species with the intention to develop a cochineal industry for the new colony. What happened to these first introductions is no known but other introductions followed and it appears that plants were being cultivated at Parramatta before 1840 and it had spread to Chinchilla in Queensland by 1843. Segments of the plants were taken to many places for use as pot plants or hedges. By 1900 infestations covered 4 million hectares in Queensland and New South Wales but by 1920 this had exploded to 24 million hectares. Despite every control effort, estimates of the plants rate of advance were 400,000 hectares (1 million acres) per year (Parsons & Cuthbertson 2001; Land Protection 2006a).

A Prickly Pear Travelling Commission was established in 1912 and members travelled overseas to look for natural enemies and their possible use in Queensland as a biological control. By 1914 two species of Cochineal (Dactylopius spp.) and Cactoblastis Moth (Cactoblastis sp.) were introduced. The Cactoblastis larvae did not mature but work with the Cochineal was more encouraging and field trials were undertaken in 1914. Within three years of release most populations of Drooping Prickly Pear at Charters Towers, Townsville and Bowen regions were destroyed (Land Protection 2006a).

Although a number of different insects including borers, suckers and mites were trialled by the Commonwealth Prickly Pear Board in 1919, following the first world war, but these were variable in success due to their specificity to certain species of Prickly Pear (Land Protection 2006a).

Cactoblastis Moth was reinvestigated in 1924. In 1925 moths were successfully raised at Sherwood and 10 million eggs were distributed to 61 localities in affected areas during 1926-1927 and a further 2.2 billion eggs released between 1927 and 1931 (Land Protection 2006a).

The insect was spectacularly successful and by 1932 the stem boring larvae had caused the collapse and destruction of the original thick stands of Prickly Pear. By 1932, almost 7 million hectares of previously infected lands was reclaimed. The conquest of the Prickly Pear is considered the world's most successful control of pest plants by biological control (Land Protection 2006a).

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This database is designed to provide information, including biological and ecological, on invasive plant species that are on a national weed list, or are legislated against in a state or territory. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. For further information on the images contained in the database please contact the copyright owner. All images in the weed identification tool are managed by the Australian Plant Image Index (APII). Various copyright conditions apply for these images. For further information on the copyright conditions of images contained in the database please contact the APII at: photo@anbg.gov.au.