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cactus pictures Prickly Pear in Central Queensland




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Prickly Pear in Central Queensland



Prickly pear (Opuntia stricta) exists on the central Queensland coast of Australia and a number of islands in the region. In most cases the plants are individual specimens; along the fore dune or beach vegetation interface of islands. Dense infestations spreading well inland of the coasts exist on some islands - in some cases this can be across the entire island. On Curtis Island, Prickly Pear is of particular concern as it has become a food source for feral pigs for which there is a major pig trapping project aimed at reducing threats to nesting Flatback Turtles (Natator depressus) and Yellow Chats (Epthianura crocea macgregori). It is believed that Prickly Pear was introduced to the Whitsunday Islands as a food source for marooned sailors. It is unknown how it reached other islands but it may have been distributed through birds or floating on water.

Prickly Pear has the ability to displace native vegetation communities including:
  • Casuarina, Spinifex, & Goats Foot Convolvulus - of concern
  • Microphyll vine forest on coastal dunes - critically endangered
  • Bloodwood, Melaleuca & beach scrub spp. - of concern
  • Spear, Blady & Kangaroo grasses on coastal dunes - of concern
It is also a threat to native animals including the Beach Stone Curlew (Esacus magnirostris) (vulnerable) and the Pied Imperial Pigeon (Ducula bicolour), & Osprey (Pandion cristatus) for which beach scrub is a known habitat. Beach Stone Curlews are particularly vulnerable as they are known to nest at the beach-vegetation interface where Prickly Pear is most common. Indirectly, Prickly Pear is also a threat to the Yellow Chat which is endangered under the Nature Conservation Act and critically endangered under the Environmental Protection and Biodiversity Conservation Act and the Flatback Turtle (Natator depressus) - vulnerable. Prickly Pear is a food source for feral pigs on Curtis Island which threaten these species. In addition pigs up root plants and cause significant damage on Curtis Island to the vegetation of the marine plane which is listed as a significant wetland.

While it is well known that insect biocontrols have virtually eradicated the pear from inland areas, to date biocontrols such as the Cactoblastis moth or Cochineal insects have been ineffective in coastal areas. It is thought that this is because Prickly Pear develops a thicker 'skin' to assist in salt tolerance. This thicker skin may be impenetrable/indigestible to larvae which leave viable portions of the plant to the extent that the pear survives. Cochineal bugs can be more effective but often require dispersal assistance. It is thought that repeated introductions of biocontrols will eradicate the pear and/or may eventually produce a generation of insect which is able to penetrate the coastal Prickly Pear

Author: Kerensa McCallie

For more information on the history of Opuntia in Australia and control measures, see these brochures produced by The State of Queensland Department of Primary Industries and Fisheries:

The Prickly Pear Story
Prickly Pear Identification and Control
Declared Plants of Queensland

Or visit their website at: www.dpi.qld.gov.au
Index of Articles
Introductory and Naming
     Wherefore Art Thou Cactaceae?
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     Cacti & Succulent Identification
     Cereus Peruvianus -The Least and Best Known Cactus
     More About Cereus Peruvianus

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     The Sun Burned Cacti
     Grafting on Pereskiopsis
     Making Your Own Cactus Soil
     Growing NON-Hardy Cacti in Cold Climates
     Tools of the Trade
     Growing Cactus with Artificial Light
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     Raising Cactus From Seed
     Growing Cacti in Terracotta

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     Interview: Cactus Conservation in Paraguay with Alex Arzberger
     The Fate of the Minnesota Ball Cactus

Variety
     A Cactus Odyssey in Arizona
     Mangrove Cactus
     Have a Cup of Cactus
     Opuntia as an Invasive Species in Australia
     The Creating of "Springtime Succulence"
     Making Botanical Illustrations
     Adapt or Perish
     Chasing the Wild Epis
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