Weevils from South America could be the breakthrough in combating an invasive weed that has been threatening South East Queensland waterways.
For the past two years, Seqwater has helped fund research into developing a biological control agent against Cabomba – one of the worst aquatic weed species in Australia.
Originally introduced to Australia as an aquarium plant, Cabomba is highly invasive and can rapidly infest waterways. 
The weed forms dense canopies below the water’s surface with infestations displacing native plants and animals, affecting water quality and impeding water users.  

Manual removal of Cabomba.
Seqwater Senior Scientist Dr David Roberts said part of the research project involved importing the Cabomba weevil from the border area of Argentina and Paraguay as the latest weapon against the invasive weed.
Dr Roberts said approval had been granted by the Federal Government to import the weevil into a secure quarantine lab at The Dutton Park Ecosciences precinct, where a research team from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Queensland Department of Agriculture and Fisheries was undertaking a series of tests.
“The research team has visited Seqwater’s lakes where Cabomba infestations are present to collected fresh samples of Cabomba for the weevils to grow on,” Dr Roberts said.
“Cabomba is native to South America and is a food source for this particular species of weevil. The weevils lay their eggs on the flower stems of Cabomba and the larvae and adults eat the plant.
“Before being released into the environment as a bio control agent, extensive research is being undertaken to assure weevils will only feed on Cabomba and not attack other plants."

Testing being conducted at the secure quarantine lab at The Dutton Park Ecosciences precinct
Dr Roberts said if the research yielded positive results, the weevil could become a valuable control tool for Cabomba.
“At this stage, the control of Cabomba is mainly limited to physical control methods such as manual and mechanical removal which can be a lengthy and costly process,” Dr Roberts said.
“Seqwater spends about $170,000 per year on Cabomba removal – and that’s just on the high priority areas on our lakes but better options are needed.”
“In addition, weed infestations can significantly add to the cost of treating water, so introducing an effective biological control agent will not only have environment and recreation benefits, but economic ones, too.
“If the research goes to plan, the CSIRO can then apply to the Federal Government to introduce the weevil as a biological control agent. This process is very thorough and could take a few years to complete and satisfy at the approvals processes.”

Cabomba weevil feeding on the weed.
Ay Cabomba!
• Cabomba (Cabomba caroliniana) is a fully submerged aquatic plant; originally a native of the Americas it was introduced into Australia as an aquarium plant.
• It was first recognised as naturalised in 1986. Since then it has become established in areas of Queensland, New South Wales and Victoria either because of having been deliberately planted for commercial purposes, or possibly discarded by aquarists.
• The ecology and life cycle of Cabomba in Australia is not well known. In the north of Queensland, it grows and flowers throughout the year, but in southeast Queensland it may stop growing and flowering in the winter months (July and August).