Update #4 - Aquatic weed clearing, Clermont and St Lawrence

Published on 17 August 2022


Isaac Regional Council has been consulting with other Councils and Biosecurity Queensland on ways to manage the recent expansion of Salvinia weed in St Lawrence and Clermont.

It is the first time Hoods Lagoon at Clermont has had an infestation and as a precaution a surveillance survey on Theresa Creek Dam indicated Salvinia was not present.

Initially used in the aquarium trade because of its hardiness and ease of cultivation, Salvinia weed rapidly covers water surfaces and damages water quality, access, and visual appeal. Its growth rates and the challenges it presents being on water and not on land, has proven difficult to control. Control programs on large infestations are very intensive and require a multi-year commitment. Residents might not see a Council officer at the sites however we are working hard to limit the impacts of Salvinia weed.



In the past six months, Council has used integrated pest management practices to attempt to control the spread of the invasive weed including:
Mechanical removal of large dense shallow mats.

  • Strategic spraying where the Salvinia is dense and mechanical removal is unsafe and or inhibited by native plants.
  • Sourcing and introducing of the Salvinia weevil (Cyrtobagous salviniae). The cold weather has impacted the effectiveness of the biocontrol, but this should improve with warmer weather.




Mechanical removal of the weed will begin at Hoods Lagoon tomorrow, Thursday 18 August 2022. Works will be ongoing while we undertake a combination of treatment options.


St Lawrence

Rainfall at St Lawrence has flushed Salvinia over the weir to the saltwater which kills the weed, and this has addressed the immediate concerns. However, it will re-establish with time and further measures need to be developed to limit the impact. The use for the town water supply limits some of the options that Council can undertake for control. Further options are being reviewed.



Council encourages residents and property owners 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


Tagged as: