3. BIOLOGICAL CONTROL OF POSSUMS
The introduced Australian brushtail possum (Trichosurus vulpecula) is a very serious pest in New Zealand. It causes extensive damage to indigenous forests and acts as the major vector of bovine Tb to cattle and deer.
Forest ecosystems are being drastically altered by the selective attention of possums which can eliminate favoured browse-species from whole tracts of forest.
The potential reduction in returns from agricultural production, should restrictions on access for meat and dairy products be imposed by our trading partners due to the presence of bovine Tb, could be up to $500 million annually.
Currently about $32 million is spent annually on poisoning and trapping possums. However, this level of expenditure is not sustainable and some current methods of control are becoming less socially and politically acceptable.
Recently research into possum biocontrol as a long-term cost-effective solution to the possum problem was initiated. However, the expectation is that control will be, for the foreseeable future, dependent on a number of technologies used in an integrated manner.
The research into biological control of possums, funded through Vote: Agriculture, owes its origin to a National Science Strategy Committee meeting held in October 1992 at which clear research priorities for biological control were established. Subsequently, MAF/DoC sought Government funding for a programme to address the priorities and Government agreed to fund the programme for three years, 1 July 1993 through 30 June 1996, at $2 million p.a. via Vote: Agriculture.
A further three years of funding totalling $6.25 million, voted in 1996, will support the programme through until July 1999.
Most of the research programmes follow one of two directions for possum biocontrol. The first involves targeting physiological pathways, such as the possum reproductive system, while the second is looking for potential pathogens.
Most of the physiological research is focusing on the reproductive system. This includes studies on gametes, fertilization, embryonic development, endocrine control of reproduction and of lactation. Essentially, the search is on for possum-specific physiological pathways which could be targeted for disruption and at this stage much of the research is fundamental.
Studies investigating possum parasites and diseases are being conducted in both New Zealand and Australia. These studies seek to identify parasites and diseases which could have an adverse effect on possums. There is no expectation that a single disease causing agent will solve the problem but it is believed that a number of different organisms could, collectively, adversely affect possums and afford some level of control - especially when added to other environmental stresses.
The surveys are also seeking candidate vector organisms which could, possibly, be genetically manipulated in order to enable them to spread disruptive genes throughout the possum population. These genes would be expressed as biochemicals which would interfere with possum reproduction or health.
Most of the programmes are designed to run over several years, so the broad objectives were not expected to be completed in 1995/96.
Research directions are set, and progress monitored, by an informal group of five which takes into account the priorities established by the Control of Possums and Bovine Tb National Science Strategy Committee (NSSC). Two members of the group, Drs Paul Livingstone (AHB) and Peter Kettle (MAF) are members of the NSSC. The three other members are Drs Ken McNatty, Richard Sadleir and Hugh Davies who are contracted by MAF to provide a technical overview of the research into possum physiology, Tb vaccine development and possum diseases.
In April 1997, a workshop to discuss research to date and future research directions will be held under the auspices of the NSSC.
MAF funded research into control of Tb and possums accounts for 21% of the national investment in this area.
Contact for Enquiries
Farm Monitoring Programme Manager
Monitoring and Evaluation
MAF Policy
PO Box 2526
Wellington
NEW ZEALAND
Phone: +64 4 894 0623
Fax: +64 4 894 0741
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