Didymo News

The words no one wants to hear ‘didymo has been confirmed in the North Island’ greeted representatives from MAF Biosecurity New Zealand, DOC and other stakeholders brought together to participate in a MAF simulation exercise for didymo (Didymo spheniagerminata) in Taupo at the end of May.

The latest findings from MAF Biosecurity New Zealand's Didymosphenia geminata (didymo) science programme were presented to the Didymo Technical Advisory Group and Long-Term Management partners at a seminar held in Wellington today.

Didymo has been detected in Queenstown Bay in Lake Wakatipu, Biosecurity New Zealand and the Queenstown Lakes District Council announced in early February.

The organism has previously been detected in other parts of the lake and has been known to bloom on the fringes of lakes where there is sufficient wave action. Didymo has been found in other lakes fed by affected rivers. Four affected rivers flow into Lake Wakatipu. Its main impact is expected to be visual only, though there is obviously a risk of spread.

Now that most New Zealanders are back to work the main risk is posed by the large numbers of independent travellers visiting the country. Targeting these travellers has been a challenge.

Employing contract workers at the Wellington ferry terminal has enabled us to get the message out to travellers before they get to the South Island. It has also produced some alarming statistics:

• More than 50% of travellers currently crossing to the South island are from overseas
• Of these, most have not yet heard of Didymo

Felt soled waders are a high risk vector for spreading Didymo. We are currently producing an information sheet and poster to ensure all anglers know how to treat their boots.

• We recommend that felt soled boots are not used by anglers fishing more than one river who are unable to guarantee to decontaminate the boots after every trip.
• Freezing boots until solid is widely accepted as the most viable method for decontamination

High profile kayaker, Mark Eames has been employed to advocate and inform kayakers and rafters across the North Island about the risk of Didymo and how to ‘Check, Clean, Dry’. Mark will also visit commercial rafting operators, retailers and kayak manufacturers and distribute a kayaker information sheet (produced by the NZ Recreational Canoeing Association)

To have any chance of controlling Didymo we must detect an incursion as early as possible. To increase our chances, a monitoring or early warning system is being implemented at critical sites throughout the North Island. Taupo/Tongariro DoC staff are conducting fortnightly sampling on high risk sites within the Conservancy. This programme will be implemented throughout the North Island by the regional action groups with regional councils in particular playing a key role.

After a huge amount of laboratory testing a potential control tool has been developed by NIWA. Chelated Copper has been extremely good at killing Didymo in laboratory conditions while having little impact on indigenous flora and fauna. As a consequence of these encouraging results, field trials are currently being undertaken in the South Island.

A further delimiting survey was carried out throughout New Zealand in January and early February. With almost all of the North Island samples analysed there is still no indication of a North Island incursion. This is fantastic news, particularly given the seemingly relentless spread through the South Island.

On the 1st October 2006 the Central North Island ‘STOP DIDYMO’ Campaign was launched at Lake Tarawera to coincide with the start of the new fishing season. ‘Clean, Check, Dry’ demonstrations were conducted and Didymo decontamination bottles were distributed.

Since then the ‘Stop Didymo’ public awareness and education campaign has focused on intercepting high risk parties travelling between waterways and more specifically, those travelling to the North Island from the South Island (Controlled Area).
Highlights include: