The potential impact of invasive, drought-resistance cacti on Western Australia’s agriculture, environment, and social amenity has been detailed in a new report.
Department of Agriculture and Food research officer Sandy Lloyd said the report provided a snap-shot of the status of weedy cacti in WA and would contribute to the development of Statewide and regional management and response plans.
“Infestations of cacti pose a serious threat to agriculture, particularly in the southern rangelands of Western Australia which are especially vulnerable to cactus invasions,” Ms Lloyd said.
“The size of infestations can increase quickly and dramatically, particularly when vehicles or floodwaters spread cactus stem segments over long distances, and the cost of control can exceed the value of the infested land,” she said.
“The new report covers a large group of cacti known as the opuntioid cacti. This group includes several prickly pear and related cacti that are species of Austrocylindropuntia, Cylindropuntia and Opuntia.”
The report documents infestations of 16 different opuntioid cacti in WA.
“This is the first time the cactus infestations in WA have been analysed and the various species named,” Ms Lloyd said.
“Most cacti can form impenetrable thickets if left un-managed, potentially dominating grazing land and other areas of the rangelands,” she said.
“They spread easily by seed and stem segments that attach to vehicles, animals and people. Segments readily take root to form new plants.
“Many of the weedy cacti were introduced as drought-hardy ornamentals for old homesteads and settlements in the Goldfields and pastoral areas.
“Sources of new infestations include abandoned and unmanaged cactus gardens, unmanaged infestations and the dumping of unwanted plants.
“Further spread of cacti in Australia has resulted from the deliberate movement of the plants for gardens via nurseries and informal outlets such as markets, fetes and garage sales.”
Opuntioid cacti vary significantly in their form and habit, ranging from low-growing shrubs to trees up to five metres tall. Their flowers generally appear in spring and summer.
Ms Lloyd said cactus infestations in other parts of Australia provided an indication of their potential impact in WA.
“Cylindropuntia rosea has long sharp spines that are strong enough to pierce heavy work boots and car tyres. The largest infestation of this species in WA is over an area about 200 hectares in the shire of Menzies, and it has great potential to spread further,” Ms Lloyd said.
“In New South Wales, the cactus infests about 60 000 hectares around Lightning Ridge and a total of about 100 000 hectares in north-western NSW.”
Ms Lloyd said based on the distribution, impact and current management of opuntioid cacti detailed in the report, it was possible to identify major stakeholders who could be involved with the management of these species.
“The stakeholders in WA are diverse and include primary producers (particularly pastoralists), natural resource management (NRM) groups, local government and government departments,” she said.
“An outstanding recent example of stakeholder investment was the Coral Cactus project on Tarmoola Station in Leonora which was funded by the Australian Government and delivered by the Rangelands NRM WA and the Goldfields Nullarbor Rangelands Biosecurity Association (GNRBA).
“Activities included building a fence around the station’s rubbish tip to help prevent further spread of cacti from the tip to other parts of Tarmoola via livestock, and feral and native animals.”
Because of the status of opuntioid cacti as Weeds of National Significance and the risks they pose to agriculture, the environment and social amenities, arrangements are being made to declare them all in WA.
The Situation Statement on Opuntioid Cacti (Austrocylindropuntia spp., Cylindropuntia spp. and Opuntia spp.) in Western Australia is available on the department website agric.wa.gov.au
Media contact: Jodie Thomson/Dionne Tindale, media liaison, +61 (0)8 9368 3937