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Supporting the fight against weedy cacti
Welcome to the Australian Invasive Cacti Network
Weedy cacti have been causing problems since they escaped from early settlements such as the Leonora district of Western Australia. A number of species of cacti had became established as weeds, spreading considerable distances from the original point of introduction. These included coral cactus (Cylindropuntia fulgida), Hudson pear (C. rosea or C. tunicata) and one of the prickly pears (opuntias).
Today, these present a potential threat to much of the arid and semi-arid parts of Australia. There are currently major infestations in Queensland, NSW, South Australia as well as the Northern Territory.
Photo - Early Prickly pear (Opuntia stricta) infestation south east Queensland
Surveys undertaken by the Rangeland NRM Alliance have shown that invasive cacti, in particular the Opuntioids (principally species of Opuntia and Cylindropuntia), pose real challenges to primary production and biodiversity at sites in all mainland states. In several regions where there were extensive infestations the costs of chemical control often exceeded the value of the land. It was also found that for most species of cacti in the rangelands there was limited or no currently effective biocontrols, though there may be potential for cochineal insects (Dactylopius spp.) to be useful with further research. The very successful biocontrol of prickly pears in southern Queensland and northern New South Wales by Cactoblastis caterpillars has not translated to drier or cooler climates.
Photo - Snake cactus (Cylindropuntia spinosior) flower
Prevention is cheaper than cure - most invasive plant species are escaped garden ornamentals, possibly more than 80%. Cacti are no different. While Biosecurity Queensland has banned the sale and cultivation of most species of Opuntia and Cylindropuntia, certain high-risk species can still be legally sold and planted in some of the other states. Hopefully, WONS-status will rectify the situation, but this might take time. Avoid planting potentially invasive cacti in your garden - once in the ground, they are "biologically released" and are free to spread
What is the Australian Invasive Cacti Network?
The Australian Invasive Cacti Network is a group of people from around Australia who are working to reduce the threat of invasive cacti to our biodiversity and primary production.
The group was formed in late 2009. Concerned that there was no coordinated approach to an increasing weed cacti problem across the rangelands, the Rangelands NRM Alliance undertook surveys of its member groups which revealed that invasive cacti, in particular the Opuntioids (principally species of Opuntia and Cylindropuntia), were posing real challenges to primary production and biodiversity at sites in all mainland states. In several regions where there were extensive infestations the costs of chemical control often exceeded the value of the land. It was also found that for most species of cacti in the rangelands (80% of Australia) there were limited or no currently effective biocontrols.
The Alliance contacted the South Australian State Opuntia Taskforce and it was agreed that a national meeting should be convened. The first National Invasive Cacti Forum was held in Adelaide in early December 2009. Representatives from the pest management community, scientists and biosecurity agency staff heard presentations on invasive cacti from most states of Australia along with information on taxonomy and biocontrol research both within Australia and South Africa. The South Australian State Opuntioid Cacti Management Plan consultation draft (2009) was released at the forum.
One of the outcomes of the forum was the agreement to form a national body, the Australian Invasive Cacti Network, to raise awareness of cacti as a significant threat to biodiversity and production along with providing a forum for exchange of information on the taxonomy, biology and control of invasive cacti. The network works closely with biosecurity agencies, research institutions, natural resource management groups and land managers. The network is open to all people or organisations with an interest in ridding Australia of weedy cacti.
Why are these cacti so bad?
Introduced cacti are highly invasive plants. Some of the worst are the Opuntioids which include the three genera: Austrocylindropuntia; Cylindropuntia; and Opuntia. Originating from the Americas, multiple species were introduced to Australia to support cochineal dye production, for stock fodder or planted as garden ornamentals or hedges.
Jumping cholla cactus (Cylindropuntia prolifera) near Longreach, Queensland - Desert Channels Group
There are now at least 27 species of opuntioid cacti that have naturalised throughout Australia, with infestations present in the Gascoyne and Goldfields regions of Western Australia; Central Australia; South Australia; Victoria; New South Wales; and throughout Queensland. Some species, such as the edible Indian fig and common prickly pear, are commonly found in backyards and peri-urban areas.
More concerning, however, is the occurrence of species in remote and sparsely populated rangeland areas.
Opuntioid cacti present a threat to grazing industries through their ability to form dense infestations that can reduce access to feed and hinder mustering activities. Their spiny habit can injure stock, damage fleeces and hides and affect the safe handling of affected animals for shearing purposes.
The risk of spine injury also applies to native wildlife, either through impalement or the lodgement of spiny segments in limbs, hides and mouths, leading to immobilisation and a painful death. Dense infestations of cacti can impede movement of native wildlife through corridors and limit access to refuges. Competition from opuntioids can also limit the growth of native vegetation, including small shrubs and groundcovers.
What have we achieved?
The Australian Invasive Cacti Network has been actively working to raise the profile of the issue of invasive cacti as a threat to biodiversity and primary production. There are now more than 100 members of the Network from all mainland states of Australia. Presentations have been made to national conferences and visits made to a number of areas where invasive cacti are a problem. In 2011 the State governments of South Australia, New South Wales and Queensland collaborated to make an application for the Opuntioid cacti to be considered as Weeds of National Significance.
Opuntioid cacti declared Weeds of National Significance
In early 2012 the Opuntioid group of cacti were declared Weeds of National Significance. This group includes all species of Opuntia (with the exception of the Indian Fig - Opuntia ficus-indica) and all members of the Cylindropuntia and Austrocylindropuntia.
The Draft Strategic Plan 2012-2017 National Opuntiod Cacti Strategic Plan was circulated in August/September 2012 for public consultation. This plan identifies the priority activities needed to prevent new infestations from occurring; manage existing infestations; and increase the capacity of people to manage opuntioid cacti.
Community and industry partnerships are contributing to integrated management of opuntioid cacti at the local and regional level, with active control programs in place throughout the weeds’ current range. A nationally coordinated program will focus on the following priority areas:
· Refine species’ distribution, including high risk areas at risk of future invasion;
· Improve understanding of opuntioid weed biology, ecology and taxonomy to inform risk management and strategic control programs;
· Provide training and resources to improve species’ identification;
· Collate and distribute information on best practice management techniques;
· Control of priority sites, including new infestations, outliers and containment approaches to reduce further spread; and
· Promote further research into biological control agents for control of core infestations.
Surveillance, early detection and eradication - if a new species of invasive cacti can be detected while the population is small, complete eradication is often feasible and cheap. Much like early detection of a skin cancer, vigilance is the key. There are numerous examples of successful eradication. Unfortunately, most go un-noticed and are not reported. Report all suspected infestations to your state biosecurity agency or local council. If you think you have found a new species of cactus, get it identified by the Queensland Herbarium.
The prickly pear story
Acknowledged as one of the greatest biological invasions of modern times, the introduction and subsequent spread of prickly pear into Queensland and New South Wales had infested millions of hectares of rural land by the 1920s, rendering it useless for agriculture. Prickly pear proved so difficult and costly to control by chemical and mechanical means that enormous areas were simply abandoned by their owners.
Find out more about the history of prickly pear by clicking on the image to the right. (Queensland Department of Agriculture, Fisheries and Forestry)