Current research (November 2023 – June 2026)

This new project will be delivered in partnership between CSIRO (Dr Kumaran Nagalingam, Leader of Weed Genomics Team, Health & Biosecurity) and NSW Department of Primary Industries (Dr Andrew McConnachie, Weed Research Unit).

The project commenced in November 2023, with the aim to support the maintenance of the primary culture of the cabomba weevil, Hydrotimetes natans, at the CSIRO laboratories in Brisbane, and establishment of a new, secondary population of the weevil at the NSW DPI biocontrol laboratories in Grafton, NSW.

By the end of the project (June 2026), it is envisaged that a healthy, viable culture of the weevil will have been transferred from CSIRO to NSW DPI, from which a steady supply of the weevil could be provided to local authorities across NSW for release into the environment to help control problematic cabomba infestations.

In addition to establishment and mass-rearing of the weevil culture, the project will also identify nursery sites throughout NSW, at which baseline vegetation data will be collected, and populations of the weevil released. Releases will be accompanied by in-field workshops with weed control practitioners and other relevant stakeholder groups. Post-release monitoring will be undertaken to evaluate the persistence and establishment of weevil populations, and changes in the foliage cover of cabomba and associated vegetation over time.

This sub-project will include the following main activities:

  • Ongoing mass-rearing and maintenance of a healthy, viable culture of the weevil at the CSIRO laboratories in Brisbane.
    • The weevil population will be sustained on healthy cabomba plants that will be regularly collected from sites in northern NSW and south-eastern Queensland.
  • Obtain further consignments of healthy weevils, field-collected in Argentina by sub-contractors located in the native range of the weed
    • Through a partnership with the Fundación para el Estudio de Especies Invasivas (Argentina), healthy weevils will be collected in the native range and imported into the CSIRO quarantine facility. Further collections will boost genetic diversity of the original population and reduce the risk of colony collapse through inbreeding effects.
  • Prepare laboratory facilities and cabomba plant cultures at NSW DPI’s biological control rearing facility at the Grafton Primary Industries Institute
    • Preparation to receive the live weevil cultures from the CSIRO laboratories in Brisbane. NSW DPI subcontractors will be supported through on-site visits by CSIRO researchers with expertise in weevil culturing methods.
  • Establish a secondary weevil colony at NSW DPI’s biological control rearing facility at the Grafton Primary Industries Institute
    • Through provision of at least two consignments of healthy, reproductively viable weevils obtained from the CSIRO culture. The CSIRO researchers will support the NSW DPI subcontractors to establish the weevil colony through the provision of detailed rearing methods and face-to-face training.
  • Identify up to five candidate nursery sites at which weevil populations will be released across NSW
    • Liaise with members of the NSW Biocontrol Taskforce, NSW Local Land Services, NSW National Parks and Wildlife Services and Landcare and other relevant stakeholders to. Sites will represent a gradient of climate contexts across the full range of the weed in NSW.
  • Undertake baseline monitoring and releases of healthy, reproductively viable lab-reared weevils at each site.
    • Up to 100 weevils will be released at each site, with replenishment as required if the primary populations die out.
  • Undertake in-field workshops/information/demonstration sessions at each site with interested stakeholders drawn from local NRM groups, to coincide with weevil releases.
  • Monitor and evaluate the target weed, associated native vegetation and weevil populations over time at each release site.
    • Surveys (using method developed by the CSIRO researchers in a previous study) will be undertaken immediately prior to release of the weevil populations, then at least every six months post-release. Contextual data will be recorded on habitat condition, vegetation type, land use history and other parameters that may influence weevil population viability over time.

Contact information

For more information, please contact Kumaran Nagalingam at kumaran.nagalingam@csiro.au.