Update #7 - Aquatic weed clearing, Hoods Lagoon, Clermont

Published on 26 October 2022


Isaac Regional Council shares the community’s frustration with the invasive weed – Salvinia molesta – and officers continue to push forward with the ongoing eradication program.

Complete eradication of a salvinia infestation is a challenging process and ongoing monitoring and follow-up treatments will be required over multiple years to remove this invasive species from Hoods Lagoon in Clermont.

Our integrated management program for this highly invasive aquatic weed involves mechanical removal, application of registered herbicides and the introduction of biological control agents.




Mesh fencing

Mesh fencing has been installed near the causeway as a temporary control measure to contain the weed.


Mechanical removal

The specialist aquatic weed harvester sourced by Council was recently called away to urgent matters required by the Queensland Government. Current discussions indicate from the contractor that on-site mechanic removal will begin in December.

Council is continuing to explore all alternative options to secure a solution as soon as possible as alternative specialist contractors in Central Queensland are limited.

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.


Weevil breeding

Our Salvinia weevils - Cyrtobagous salviniae - are growing nicely and look promising for release in the not-too-distant future.

While an effective control, the weevils are not expected to produce instant results.

Weevils need time and favourable conditions to build up a population that will reduce an infestation, and it is difficult to generalise about the time required.

Weevils usually reduce an infestation in two years, sometimes less in tropical and subtropical climates.

In temperate climates it can take three or more years for weevil populations to increase enough to reduce an infestation.


Herbicide control

Officers began herbicide control of the gully and properties downstream from the causeway earlier this month once the water volume from the lagoon slackened.

Residents are asked to steer clear of biosecurity tape cordoned off at Hoods Lagoon where the disposal of Salvinia weed will occur.



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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