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Understanding the direct and indirect environmental impacts of biocontrol agent introductions to inform future decisions

This project ran for five years until 2022.  Researchers analysed previous biocontrol introductions to assist in predicting and evaluating direct and indirect risk from new organism introductions.

Project abstract

EPA decision-making under the HSNO Act carries uncertainty about risks and benefits of approving new organisms for release. Our research aimed to reduce the level of uncertainty by investigating the impact of biological control agents (BCAs) which have been approved and released. We also investigated potential indirect effects by examining tri-trophic interactions and building food-webs. Information contained within taxonomic collections such as the NZAC was mined for host: parasitoid records to support the project. A new tool (scale-of-risk) was developed to help predict risk of new BCAs relative to those already introduced. Case studies for two BCAs, Cotesia urabae (released to control Uraba lugens) and Microctonus species (for forage weevil pests) were examined post-release to determine evidence for non-target (NT) impacts. For C. urabae a sentinel field experiment indicated that this parasitoid was safer in the field than was predicted from pre-release host range tests. Microctonus species were found at five of nine native tussock grassland sites and nine species of native weevils were found to be parasitised by at least one of the two M. aethiopodes biotypes. The native weevil genus Nicaeana, was found to be particularly susceptible to parasitism. Indirect NT effects of BCAs were assisted by the development of food webs, which allowed visualisation of interactions between plants, herbivores and BCAs. Data mining from taxonomic collections informed key aspects of risk from BCAs. Models confirmed that NT species are attacked more by generalist than specialist BCAs, but also that NT attack records increase as more sampling is carried out and records become available. Development of the scale-of-risk tool progressed well but requires further work in a new project. Post-release studies are a useful source of information for the EPA and DOC to assess the accuracy of predictions made to support approval to release . This has increased confidence in regulator decision-making by validating previous decisions, developing capacity of applicants to determine indirect effects, providing an online resource to search for host: parasitoid relationships, and a tool to assess risk of a proposed BCA relative to previous introductions.

Biosecurity outcome

  • A new tool will be developed from the analysis of previous biocontrol introductions to assist in predicting and evaluating both direct and indirect (e.g. food-web/ecological effects) risk from new organism introductions to assist DOC and EPA in their analysis of applications and provide EPA assurance and certainty in decision-making.
  • A new ‘scale of risk’ tool to assist in BCA risk prediction which will provide a comparative measurement of where on the continuum a new proposed BCAs is likely to fit.

Science outcome

  • New knowledge on the direct and indirect impact of BCAs based on food-web analysis.
    • Case studies of post release impacts of recent introductions for Cotesia urabae and Irish Microctonus aethiopoides.
    • New data sets for non-target host information: a) taxonomic collections (e.g. historic records of target and non-target effects, taxonomic literature); b) molecular evidence (host DNA from adult parasitoids).

For publications and more information on this project and others visit Zotero.

Access to Zotero can be found on the B3 homepage under ‘Outputs’.