Didymo Stakeholder Update - December 2006

22 December 2006

November Delimiting Survey Results

Three delimiting surveys have been planned for the 2006-07 summer didymo surveillance programme.

109 high risk sites were sampled as part of the November 2006 national delimiting survey. Bad weather causing flooding meant that several sites (11 of 130 total) were not sampled.

Only two sites tested positive, both in the South Island. The site on the lower Waihao River near SH1 north of Oamaru is the first positive for this river. The second positive site in the survey was on the Clutha, a river that first tested positive several months ago.

The second survey for this summer is planned for late January, with the third in the series expected to follow two months later.

North Island Strategy

A North Island detection contingency plan is in place. Development of this plan included Biosecurity New Zealand, our contractors and long-term management partners.

A high level outline of our North Island response strategy follows:

  • Upon receiving a confirmed positive in the North Island, Biosecurity New Zealand will immediately deploy three staff to the site to run the response, conduct public awareness/social marketing and media work, and organise any logistics necessary.
  • Three pieces of work will begin in parallel:

    1. a survey to determine didymo distribution;

    2. an intensive social marketing campaign to minimise spread while the survey is being undertaken. The campaign will encourage people to avoid the affected area; and

    3. the collection of information to determine the feasibility of using any control tools that may be available at the time.

      1. As soon as possible, based on the distribution and other information gathered, Biosecurity New Zealand will make a decision in consultation with long-term partners on whether it is appropriate to attempt to eliminate didymo from the North Island. This decision will be based on information including:
          • technical feasibility;
          • cost-effectiveness;
          • probability of success, including the likelihood of re-infestation;
          • legal feasibility;
          • wishes of the local community; and
          • presence of high value sites or high value species.
      2. If elimination from the North Island is to be attempted, a plan which has been developed to use copper chelate will be actioned and a Controlled Area under the Biosecurity Act 1993 will be established around the affected areas. If not, a Controlled Area is unlikely to be established and the primary activities will be encouraging water users to change their behaviour to reduce the spread.
      3. The final decision on action will rest with Biosecurity New Zealand in consultation with stakeholders.

      Felt-Soled Waders Update

      • Wherever possible, we recommend you use rubber-soled waders rather than felt-soled waders. Research has shown the risk of spreading didymo with felt-soled waders is extremely high, especially compared to rubber-soled waders.
      • For decontaminating felt soles:
        • Combining the power of heat with the power of detergent is highly recommended due to the inability of decontamination solutions at ambient temperatures to easily penetrate felt soles. The entire felt sole needs to be completely immersed for 30 minutes in hot tap water (45 to 50 °C – uncomfortably hot to touch) containing 2% dishwashing liquid or nappy cleaner.
        • If hot water alone is used, careful attention needs to be made to ensure the temperature of the water is maintained above 45 °C for 40 minutes to ensure the interior of the felt reaches a sufficient temperature.
        • Alternatively, freezing the item until solid is effective.
        • Relying on drying is not recommended because of the difficulty in determining when the entire thickness of the felt is thoroughly dry.
      • These findings for felt soles can be extrapolated to other dense, absorbent materials.

      Science Update

      The resource consent has been granted for a January river trial of the chelated copper control tool in a creek in Southland.

      The Biosecurity New Zealand didymo website will be updated today to include research reports from the 2006 science programme and revised cleaning methods for fresh water activities.

      To report an exotic pest or disease, call the MAF Emergency Pest and Disease Hotline: 0800 80 99 66.