UPDATE #8 Aquatic weed clearing, Hoods Lagoon, Clermont

Published on 11 November 2022


Isaac Regional Council’s multi-faceted approach to the highly invasive aquatic weed – Salvinia molesta – continues to push ahead as the challenging process towards removal continues.

Council shares the community’s frustration in tackling this persistent problem, with ongoing monitoring and follow-up treatments required over multiple years to remove this invasive species from Hoods Lagoon in Clermont. The Isaac region is not alone in its battle against Salvinia, with many council’s across Queensland encountering the same challenge of eradicating this highly invasive species.

The multi-faceted approach involves mechanical removal, application of registered herbicides and the introduction of biological control agents.

Weevil breeding

Locally bred Salvinia weevils have been released at Hoods Lagoon in PVC pipes to assist with the removal of the aquatic weed infestation. While an effective control, the weevils are not expected to produce instant results.

The weevils should spread in large numbers over the coming months and eat through the leaves on the plant causing it to die off. Weevils can take up to two years to reduce an infestation, sometimes less in tropical and subtropical climates.

If residents notice PVC pipes at Hoods Lagoon, please do not retrieve them as they house the weevils and are important to ongoing management of Salvinia weed.

The locations for the weevil release were chosen for the accessibility to sunlight and primary plant growth. As part of Council’s biocontrol breeding program, officers have ensured they are acclimatised.

Mechanical removal

Timing of the specialist aquatic weed harvester sourced by Council indicate the contractor is expected to be on-site for mechanic removal in December, weather permitting. Sourcing the harvester has been a challenge as other government agencies are also battling with the Salvinia weed infestation in their areas.

Council has also purchased two aquatic skimmers which will further assist with the mechanical removal of smaller remaining sections of weed after the use of the aquatic harvester.

Mesh Fencing

Mesh fencing was installed near the causeway as a temporary control measure to contain the weed last month.

Herbicide control

Residents are asked to steer clear of biosecurity tape cordoned off at Hoods Lagoon where the disposal of Salvinia weed will occur. Herbicide control of the gully and properties downstream from the causeway will continue to be undertaken where required.


Council encourages residents to not dispose home aquarium and pond plants into our waterways.

Property owners are reminded to be vigilant and if you suspect Salvinia on your property, contact Council’s Customer Service Centre on 1300 ISAACS (1300 47 22 27) for identification and information.

Visit https://profiles.ala.org.au/opus/weeds-australia/profile/Salvinia%20molesta for more information.


Chief Executive Officer


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