Battle to destroy Salvinia weed at Lake Macquarie

A biological battle has been underway at Lake Macquarie to bring down one of Australia’s worst weeds.

Council has now partnered with Crown Lands to try and control the Salvinia weed that has been growing on Muddy Lake since late 2020 infesting up to 25 hectares of the waterway. 

The weed is one of the worst for invasiveness, spread and impact on the environment – it can double in size every three days in ideal conditions and forms a dense mat on the water blocking light and oxygen from the water below.

One step Council has already taken to try and control the weed is releasing a tiny weevil into Muddy Lake.

The weevils feed on the Salvinia weed and their larvae tunnel into the plant’s stem causing the weed to lose buoyancy and sink. It’s already started to work with large areas of the lake visible again and many of the water birds that left have returned.

The weevils aren’t enough to eradicate the weed though which is why Council has partnered with the NSW Government.

Crown Lands and Council are working with the University of NSW’s Water Research Laboratory to investigate potential options to reinstate tidal flows at Muddy Lake. Other potential options to control Salvinia include manual removal of the weed which is expensive and ongoing, or the use of herbicide which is not supported due to potential impacts to the surrounding environment.

“Muddy Lake is home to wetlands, water birds and green and golden bell frogs so is an important ecosystem that we want to keep healthy. This joint project will help us better understand the causes of the weed outbreak and hopefully lead to more ways to better manage it long-term,” said Lake Macquarie MP Greg Piper.

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