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New project to tackle cacti infestations in the Pilbara

A new partnership in the Pilbara will work to contain significant infestations and major outbreaks of cacti in the region.

The Pilbara Corridors Project, Pilbara Mesquite Management Committee (PMMC) and DAFWA will partner in the project funded through the Australian Government’s Biodiversity Fund.

Introduced cacti are highly invasive plants and some of the worst are the Opuntioids.

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.

Rangelands NRM Program Manager (Pilbara) Dr Bill Cotching 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.

“Most invasive plant species (possibly over 80 per cent) are escaped garden ornamentals and the cacti are no different,” he said.

Surveys undertaken by the Rangeland NRM Alliance have shown that invasive cacti, in particular the Opuntioids, 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.

The project will include visual surveys and collections through all of the towns in the Pilbara in order to raise awareness, identify locations of cactus weed infestations, and remove identified cacti when in small numbers.

“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,” Dr Cotching said.

Their spiny habit can injure stock, damage fleeces and hides and impact on 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.

“This new project will instigate a campaign for the public to report cactus occurrences to DAFWA,” Dr Cotching said.

Fact sheets of declared species and species of concern together with ID photos will be prepared, printed and made available on the PMMC website. A staggered media information campaign on radio and in local newspapers will be run before each town survey. Control actions will be collated on the Pilbara Spatial Weed Management Information database.

Dr Cotching said three areas around old station homesteads that have cactus infestations will be treated by contractors.

“It is hoped that the project will result in no new infestations of invasive opuntioid cacti in the Pilbara, targeted on-ground cactus control is effectively and efficiently undertaken on known, and the risk of cactus weed invasion is reduced,” he said.

Image: Opuntia cacti (©J Bradley)