Rangelands NRM Blog, News & Resources

Prickly acacia weed reduced by ninety per cent

WA’s largest infestation of prickly acacia weed has been reduced by 90 per cent in the two years, as part of an East Kimberley weed control project.

A collaboration between Rangelands NRM and Ord Land and Water, the federally-funded Caring for our Country (CfoC) weed control initiative was carried out on an infestation covering approximately 12,000 ha of Indigenous land on the western side of Cambridge Gulf in the East Kimberley.

“Categorised as a weed of national significance, prickly acacia (Acacia nilotica) is a thorny shrub or tree that grows up to 10 metres in height,” Ord Land and Water coordinator Dick Pasfield said.

Mr Pasfield said whilst the infestation was largely confined to the East Kimberley, without the control project there was considerable potential for further spread and greater impact within the rangelands.

“The infestation of prickly acacia was located in an extremely remote region, which was not accessible by vehicles, so helicopters were used to treat the area with chemicals,” Mr Pasfield said.

The main control program was carried out just before the wet season in 2010, 2011 and 2012. Then in June of this year, Ord Land and Water were assisted in the dry season control program by the Ballengarra ranger group.

“We are delighted with the reduction of the weed density and progress to date,” Mr Pasfield said. “We’ve gone from 180 plants per 100 hectares in 2010 to 119 plants per 100 hectares in 2011 to only 5 plants per 100 hectares this year.”

Prickly acacia has economic, environmental and social impacts. Under the Agricultural and Related Resources Protection Act 1976 (ARRPA), the weed has been declared an eradication target for the entire state.

The effect on native pastureland is to create a barrier of thorny trees which can reduce pasture production and impact stock production. Environmental impacts include a loss of wildlife habitat, erosion and a decline in biodiversity. For Indigenous communities it can restrict traditional use of land and water, and limit access to recreation sites.

The Kimberley Rangelands Biosecurity Group provides additional funds to the project.

For more information contact Dick Pasfield at Ord Land and Water.