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Didymo delimiting survey well advanced

DATE Thursday 6 October 2005

Didymo delimiting survey well advanced, North Island testing to start.

Testing of North Island rivers for the presence of the invasive Didymo algae will start on Friday 7 October 2005, Biosecurity New Zealand (BNZ) announced today.

The North Island testing plan will prioritise nationally-significant waterways including the high value rivers on the volcanic plateau and Waikato River. The survey is based on NIWA’s likely environments model which estimates the suitability of all New Zealand rivers for the establishment of Didymo. This model shows that 73 percent of rivers with the most suitable habitat for Didymo are in the South Island. The North Island survey will take in some 160 sites, with sites outside the Taupo, Tongariro and Turangi area surveyed next week.

South Island waterways testing continues. BNZ has divided the South Island into thirds. Testing in the northern third, extending as far south as Kaikoura, is well advanced. Each third should take a week to complete, with the lower two-thirds to be tested in the next fortnight. The survey will also include Stewart Island.

Updates on any confirmed new finds will be issued by testing region once results are available. This is to be able to show which areas are clear of Didymo rather than release results on a piecemeal basis and create potential for confusion.

BNZ is committed to finding ways of managing Didymo, whether that is eradication, control, slowing the spread, or minimising the impacts and protecting high value areas.

Biosecurity New Zealand staff are being assisted in the testing programme by staff from NIWA, AgriQuality New Zealand, the Department of Conservation, Fish and Game, and various regional and district council staff. Waterways user groups continue to be hugely supportive and are working with BNZ to work out how cleaning methods can work best for their particular activity.

An extensive Didymo public awareness campaign is planned. To date, BNZ has sought to communicate to river users through stakeholder organisations like national river recreation associations, regional councils, Fish and Game, Maritime New Zealand and the Department of Conservation and will continue to do so. Media reporting has been particularly effective in promoting awareness of Didymo and treatment measures for users of waterways.

Next stages involve distributing information on inter-island ferries and a paid advertising campaign. Public meetings are also planned in key areas to discuss matters directly with users of waterways and other interested people.

To date, Didymo has been confirmed in Southland’s Waiau, Oreti and Mararoa Rivers, the Upper Clutha and Hawea River in Otago and the Buller River in the Tasman District. However, all rivers should be treated as suspect and the appropriate cleaning methods used.

Biosecurity Controlled Areas remain in force in Southland, Buller and Hawea. These will be reviewed at the end of the delimiting survey. No further Controlled Areas are planned in the meantime.


Background information

Biosecurity New Zealand notes the following:

– Recent Didymo finds do not indicate rapid spread, but rapid detection of Didymo. Didymo is a microscopic organism, often difficult to detect, which is now blooming, making it more visible.

– Didymo is present in a number of Northern Hemisphere countries. No control or eradication methods to rid Didymo from waterways have been developed. Products such as Aqua-Gel work on multi-celled plants in still water such as lakes and ponds, but have not been shown to be effective in controlling single-celled algae on the bottoms of flowing rivers.

– Finding a solution involves finding control methods that do not create a greater environmental problem.

– There is a lack of scientific information about Didymo. Due to the research completed since the Southland incursion was first confirmed in October 2004, New Zealand has become a world expert on this organism.

– It is likely that recent finds pre-date the initial Southland incursion and are only coming to notice now as blooms form.

– To ensure you do not spread Didymo, wherever possible use equipment, boats, clothing and other items for exclusive use in a single waterway.

– If you are moving items between waterways you must:

1. Inspect: Before leaving the river, remove all obvious clumps of algae and look for hidden clumps. Leave them at the affected site. If you find any later, do not wash them down drains. Treat them with the approved cleaning methods below, dry them and put them in a rubbish bin.

2. Clean: Soak and scrub all items for at least one minute in either, hot (60°C) water, a two percent solution of household bleach or a five percent solution of salt, nappy cleaner, antiseptic hand cleaner or dishwashing detergent. A two percent solution is 200 ml, a five percent solution is 500 ml (two large cups), with water added to make 10 litres.

3. Dry: If the above cleaning is not practical, after the item is completely dry to touch, wait an additional 48 hours before contact or use in any other waterway.

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