Work to contain an outbreak of the invasive weed water lettuce is continuing in Moore Park Beach lagoons and has already seen significant reduction in its coverage.
Bundaberg Regional Council’s natural resources management team, in conjunction with a local contractor, has been applying a herbicide treatment by drone.
Floating booms have been placed across the lagoon at a number of locations to restrict the movement of the water lettuce back into already treated areas, and to reduce the physical area where herbicide treatment is required.
Water lettuce is a restricted invasive plant under the Biosecurity Act 2014 and, by undertaking this work, Council is meeting its general biosecurity obligations as a landholder to take reasonable steps to minimise the risk the aquatic weed poses.
Operational Supervisor Natural Resource Management Greg O’Neill said Council continued to implement this long-term management strategy which focused on containment in the short-term, with eradication the end goal.
“Spraying with an approved herbicide using a drone is the most practical control method for this large water lettuce infestation in such shallow lagoons,” Greg said.
“Council is adopting a staged approach to the treatment of this infestation so we can monitor its effectiveness and minimise any potential impacts on the surrounding natural environment.”
Manual removal of the water lettuce outbreak may be required in areas where herbicide treatment is not possible, but applying this treatment remains the current focus.
He said Council hoped to further minimise any potential environmental impacts by incorporating a biological control into the management program.
“Our team has undertaken research into the safest and most effective control options and consulted with neighbouring Councils which have also been impacted by this invasive species.
“We’re now aiming to incorporate biological control into the management program, by releasing a weevil whose larvae assist with killing the water lettuce.
“We appreciate that this work has been going on for some time and thank the community for its patience while we continue to implement this long-term strategy.”
What is a water lettuce outbreak?
Under the Biosecurity Act 2014, water lettuce is classed as a category 3 restricted plant and cannot be sold, given away or released into the environment.
According to the Department of Agriculture and Fisheries (DAF), water lettuce is a free-floating aquatic weed that rapidly forms dense mats covering rivers, dams and irrigation canals.
“It can restrict water flow, increase water loss by evapotranspiration and can serve as a breeding ground for mosquitoes,” a DAF fact sheet explained.
“It creates a dense cover on the water surface that prevents light penetration and exchange of gasses.
“This leads to a drop of oxygen in the water which is detrimental to the aquatic ecosystem.”
DAF said that, while the origins of water lettuce were unclear, it was introduced to Australia as an aquarium and water garden plant and had now spread throughout eastern Queensland due to flooding and disposal of unwanted plants in natural waterways.