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Biological control of gumleaf skeletoniser

From MAF BNZ Report to Forest Biosecurity Consultative Committee, July 31 2008.

  • Gumleaf skeletoniser is an Australian moth that continues to create problems in the greater Auckland region on eucalypts and a range of amenity tree species. GLS has now been found in Huntly, Hamilton and Cambridge, so appears to be becoming established in the Waikato region.
  • Work on biological control of gumleaf skeletoniser has been underway for some time, funded largely by MAF. A Sustainable Farming Fund grant has been secured by the Gumleaf Skeletoniser Stakeholder Group to support Scion in continuing the project until 2010. This project is co-funded by FRST, FIDA (Forest Industry Development Agenda), FBRC and Farm Forestry Association, along with industry and Regional Council support.
  • Scion entomologists have narrowed the potential agents down to two parasitic wasps: Cotesia urabae and Dolichogenidea eucalypti (Hymenoptera: Braconidae). Both wasps are believed to attack only gumleaf skeletoniser caterpillars. They lay their eggs inside the host caterpillar and the parasitic larva eventually emerges, killing the host.
  • Host range testing is underway in quarantine in Rotorua on Cotesia urabae to determine the safety of this species against native and beneficial Lepidoptera in New Zealand. A range of choice and no-choice experiments are underway against five non-target species. Preliminary observations have shown that the parasitoid is willing to attack four of these species when confined together in a small dish. However it is too soon to determine if this attack will have any significant effect on the wellbeing of the caterpillars, or if they would pose any threat to the caterpillars in the wild. The answers to these questions will become clearer once the results of the experiments are obtained. Further experimentation will be done on the other parasitiod species, Dolichogenidea eucalypti, when it becomes available.
  • Once the most suitable parasitoid has been identified, and host range testing and community consultation are complete, an application will be submitted to the Environmental Risk Management Authority (ERMA) to gain approval to release the insects in New Zealand. If the application is successful, releases of the biological control agent will then be made with the help of councils and forest owners in regions affected by gumleaf skeletoniser.
  • There are no further updates on Gumleaf skeletoniser as at 24 July 2008

John Sanson



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