Shark Attack on Cabomba Infestation

The first intensified application of the herbicide Shark on the aggressive and invasive aquatic weed, cabomba (Cabomba caroliniana), has been completed with promising results.

Located in a one kilometre downstream section of the Darwin River known as Lok Landji Billabong, cabomba is a fully submerged aquatic plant native to the Americas.

Originally introduced to Australia as an aquarium plant, it is recognised as one of the 32 worst weed species in Australia and as such is listed as a Weed of National Significance (WoNS).

Cabomba Eradication Program Manager Chris Collins said the Northern Territory Government had intensified its program to eradicate cabomba from the Top End.

“The eradication program focuses on three key actions,” Mr Collins said.

“We have extended the quarantine order to ensure that nobody enters the infested area, implemented powers to take legal action for breaches of the quarantine zone and intensified our treatment of the weed with aquatic herbicide, Shark.”

“Early results indicate that the first intensified application of Shark is taking affect.

“Within seven days we were able to see cabomba showing signs of ill health.

By three weeks we could see reduced infestation and density levels.

“Remaining cabomba plants were starting to lie flat and beginning to rot.”

As part of the treatment program, a bund wall has been constructed across Darwin River, on the downstream side of the bridge on Cox Peninsula Road.

The bund wall prevents the potential flow of the herbicide into Darwin Harbour before it naturally breaks down, and allows for scientific monitoring of cabomba, the environment and water quality.

The herbicide, which has been used to successfully eradicate cabomba in other Australian jurisdictions, is applied under strict guidelines.

The water held back by the bund wall is subject to a NT EPA Waste Discharge License to ensure that suitable environmental management systems are in place.

“Extensive monitoring is conducted throughout the treatment process and to date we have seen no impacts downstream of the treatment zone and very limited impacts on non-targeted plants, fish or animals at the application site,” Mr Collins said.

“We deliberately chose a herbicide that does not accumulate in the environment.

“Water quality monitoring has shown the Shark to break down rapidly, to the point that it is not even detectable in the water being discharged.

“The spread of cabomba could be extremely detrimental to the whole of the Northern Territory’s wetlands from a range of perspectives including fishing, tourism, water quality and the economy.

“It is vital that we eradicate cabomba and protect our waterways.”

“In mid‑November a full assessment of the first application will be done to ascertain how effective it was in progressing the eradication goal.”

Go to www.nt.gov.au/cabomba for more information