Exotic weed found lurking in Ross River

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vExotic weed found lurking in Ross Riverv

News release | 25 May, 2012 - Qld DPI


An exotic weed that poses significant risks to the environment and agriculture has been detected in Townsville's Ross River for the first time.

Biosecurity Queensland officers have removed a clump of Limnocharis after it was spotted in a narrow side-channel of the river 200 metres upstream from Aplins Weir.

The aquatic weed is a Class 1 declared pest because of its invasiveness and ability to invade wetlands, rivers and dams where it can displace native plants and animals.

Biosecurity Queensland officer, Roger Winton, said Limnocharis produced small cup-shaped yellow flowers every two months and was similar in appearance to water hyacinth.

"While it looks a lot like water hyacinth, Limnocharis is much larger, growing up to one metre in height," he said.

"In this case, we removed about half a dozen mature plants and about a dozen smaller ones tucked away on a floating weed island, as well as 40 seed pods that were starting to split.

"The biggest concern is that each plant has the ability to produce nearly 1000 seeds every time it flowers and these either make the infestation worse, or they simply float away to create a new problem elsewhere.

"If left unchecked Limnocharis will clog waterways, reduce water quality and restrict water flow."

The clump of Limnocharis was spotted in the Ross River by local botanist Greg Calvert who was familiar with the weed and the threat it poses.

Mr Winton said Limnocharis had been previously detected and eradicated in Townsville at Black River, Kirwan and Pimlico.

"The seeds can stay alive in the soil for up to eight years, so whenever there's an infestation, we need to monitor the site closely for a long time afterwards," he said.

Limnocharis can be identified by its triangular stem and bright yellow flowers.

It was first found in Australia in 2001, with infestations so far being limited to North Queensland between Townsville and Mossman.

The weed is believed to have been introduced by gardeners who were unaware of the severe damage caused by Limnocharis in Asia to rice paddies, irrigation channels and drainage ditches.

Limnocharis is a target of a national cost-sharing eradication program.

Thirty known infestations have been recorded in North Queensland, with almost half now officially eradicated.

Residents who think they have seen Limnocharis, should call Biosecurity Queensland on 13 25 23.