Pouncing on Salvinia outbreak in Kakadu

10 August 2005

Kakadu park rangers have acted quickly to treat an outbreak of the invasive water weed, Salvinia, in the popular boating area of Yellow Water.

“On Monday afternoon an Aboriginal tour boat operator Yellow Water Cruises guide spotted patches of Salvinia and rapidly alerted Kakadu rangers,” Acting Park Manager Paul Styles said today.

“Our rangers have since identified numerous other small infestations scattered over about two kilometres of one branch of the Yellow Water billabong system. As this damaging weed can be spread by boat propellors, the infested area has been closed and the cruise operator tourism industry has agreed to take a new route while we treat the weed with an appropriate herbicide.

“It's vital in controlling this weed to act quickly, because it spreads so rapidly.”

Salvinia is a Weed of National Significance. A native of Brazil, it has caused serious damage from Asia through Africa, the Pacific and the United States. It is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread and economic and environmental impact.

Salvinia is a free floating fern that can eventually choke waterways. It floats on still or slow-moving water and can grow rapidly to cover the entire water surface with a thick mat of vegetation. This shades out any submerged plant life and impedes oxygen exchange, driving out fish and other animals. Even a tiny fragment of the plant left behind can regrow and rapidly cause a major infestation under the right conditions .

“Infestations of Salvinia occur over a large range are widespread on the east coast,” Paul Styles said. “It's been present in other areas of Kakadu for many years, but we manage it though a biological control agent, a tiny weevil which attacks the growing tip of this particular fern alone.

“Yellow Water has remained Salvina-free until now, and it 's very disappointing to see it here.

We ask anglers and boat drivers: please let us know immediately of any other infestations you see. Please help us too by checking your boats, vehicles and gear for plant material and removing it before leaving the boat ramp ... ”

Weed control costs Australia $4 billion a year. Weeds are fast becoming Australia's number one environmental problem.

For further information: Margot Marshall 0418 624 847
For the Salvinia fact sheet visit www.deh.gov.au/biodiversity/invasive/publications/s-molesta.html.