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  • Possums are one of New Zealand's biggest pests. Currently they are controlled by poisoning and trapping, but this is expensive and ongoing. Biological control has the potential to provide novel ways to control possums, and combined with conventional control methods, may offer more sustainable solutions.

    Why possums are a problem

    Possums are a pest in New Zealand. They eat the native trees, birds and invertebrates, and destroy ecosystems. They can also spread tuberculosis, which has a huge financial impact on the dairy and beef industries.

    Current methods of control

    Possums are currently controlled through trapping and poisoning (using mainly 1080). These methods are very costly and in the case of poisoning, not specific to possums.

    What is biological control?

    Biological control, or biocontrol, is the use of a living organism, or the product of a living organism, to control the numbers of another organism, usually a pest. Biocontrol can be defined in several ways, to find out more:

    Biocontrol methods are:

    • sustainable, having ongoing, permanent effects
    • specific to the species being controlled.

    Methods of biocontrol

    Scientists in New Zealand explored several biocontrol methods for reducing possum numbers. These included using toxins or vaccines against possum fertility. Further information on these two examples are in the articles: Hormone-toxins to reduce possum fertility and Vaccines to reduce possum fertility.

    There are a number of ways biocontrol agents, like toxins or vaccines, can be delivered to possums. We need to consider the advantages and disadvantages of each method of delivery before we decide which option to use. Find out more in the article, Delivering biocontrol agents to possums.

    This article provides explanations of key terms and definitions in possum biocontrol.

    An update

    In a 2011 report, Dr Jan Wright, Parliamentary Commissioner for the Environment, wrote that although significant research effort and resources were put into possum contraceptive vaccines and hormone toxins, funding for the projects finished in September 2010. There was concern about the length of time required to produce results, risks associated with the biocontrol agents and potential controversy over genetic engineering.

    Related content

    This article outlines some initiatives working to achieve New Zealand Government’s vision of becoming predator-free by 2050.

    Can we make New Zealand pest-free? Be inspired by Zealandia’s overview and pest free resources.

    Biocontrol was a potential answer to the controversy surrounding 1080. Read about 1080 in this introductory article.

    Useful links

    Read the full report on challenges for pest management in New Zealand on the Royal Society New Zealand website.

    For an update on emerging issues in New Zealand pest management, including vertebrate pests listen to this RNZ programme from 2014.

    Read about the findings from a study that collated the results of a number of individual studies relating to possum control and the links to biodiversity outcomes

      Published 1 December 2005, Updated 17 September 2018 Referencing Hub articles
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