The flush of fresh water through the north's river systems is giving a free ride to one of Australia's most ominous weeds - hymenachne.

With the wet season well and truly underway, the flush of fresh water through the north's river systems is giving a free ride to one of Australia's most ominous weeds - hymenachne.

Hymenachne is high on the list of Australia's most notorious weeds - and it is thriving in the sensitive environments of tropical Australia, including coastal Queensland and the Northern Territory.

Leading the charge, Biosecurity Queensland's North Queensland-based program coordinator Rob Cobon said hymenachne could quickly spread within a catchment, choking waterways, stifling natural ecosystems and interfering with its agricultural and human use.

"It was originally introduced as a fodder source for use late in the dry season when grown in ponded pasture facilities or storages to retain rain water run off," Mr Cobon said.

"However, the grazing benefits are marginal in many areas.

"Hymenachne's robust stems enable it to withstand prolonged dry seasons in both seasonally flooded and permanent wetlands.

"It has spread prolifically by mass seed production, and vegetatively from grazing areas to waterways, shallow wetlands and irrigation ditches.

"National distribution now includes northern New South Wales, coastal/central Queensland and the floodplains of Northern Territory."

A Weed of National Significance (WONS), hymenachne (Hymenachne amplexicaulis) is also known as "olive hymenachne" in the Northern Territory to avoid confusion with the native species, Hymenachne acutigluma, which is widespread across Northern Territory floodplains.

Mr Cobon said a national ban of sale and trade of the plant material was in place in all states and territories.

"The declaration in Queensland requires landholders to take reasonable steps to manage hymenachne," he said.

"Water, animals, vehicles and machinery can spread the weed, emphasising the need for ongoing surveillance and strategic control when new infestations are detected."

Mr Cobon said at a recent meeting of the National Hymenachne Management Group in Darwin, delegates further developed the national management protocols to assist the progress and implementation of the National Hymenachne Strategic Plan.

"The plan aims to reduce the adverse impacts of hymenachne by implementing actions associated with four main goals," he said.

"These are to prevent spread, minimise impacts, achieve national coordination and prevent the release of additional ponded pasture species with weed potential."

He said stakeholders had already invested considerable financial resources, time and effort into projects to control the weed.

"National coordination keeps open the lines of communication between all stakeholders to deliver latest information on preventative and strategic management," he said.

"Limiting weed spread is the responsibility of the entire community, and awareness of the potential impacts of WoNS in certain regions is a key component of this.

"For example, fishers should be aware of the potential hymenachne has in reducing fish habitats and that they can assist with early detection of outbreaks and cleaning out boats responsively to help sustain the recreation they enjoy."

Technical information and support is available for landholders managing hymenachne through local governments and natural resource management bodies with property planning, mapping, surveillance, possible incentives and control advice.

Awareness resource kits with a range of information products, including the Hymenachne Management Manual, are available in hard copy, and WONS information is also available from Biosecurity Queensland website.

There is a Commonwealth, state and local government-funded management program for hymenachne underway.

Community groups and landholders wanting to know how they can control the weed on their property can call Biosecurity Queensland for more information.