Didymo Stakeholder Update - March 2007

2 March 2007

Didymo control trials conducted

Environmental trials of a potential didymo control tool were conducted near Te Anau in mid-February. The trials, of a chelated copper formulation, were conducted by NIWA under contract to Biosecurity New Zealand. They proceeded with resource consent from Environment Southland and approval from the Environmental Risk Management Authority.

The trials were conducted over a 9.5-kilometre reach of creek by NIWA staff, assisted by staff from the Department of Conservation, Fish and Game, and Environment Southland.

The chelated copper formulation has been manufactured in such a way that the copper ion is bound to organic compounds that reduce its toxicity in aquatic environments. The specific organic compounds used in the formulation were chosen to be readily absorbed by didymo compared with other organisms.

NIWA has conducted a staged process to evaluate potential control tools for didymo by first reviewing over 3000 reports related to potential algicides. In the first stage of the laboratory trials, 10 potential control compounds were screened for their effectiveness at killing didymo. The four top candidates were evaluated in the second stage for their toxicity against other algae, invertebrates and juvenile fish. The chelated copper formulation emerged as the most effective of the compounds trialled in these laboratory tests, while exhibiting minimal toxicity to other aquatic life. The third stage includes the environmental trial, which is necessary to determine if the effectiveness and safety of the formulation under laboratory conditions will translate to a natural environment. It is also expected the field trials will provide information on how the formulation, if impacts are acceptable and it proves to be effective, might best be used as a practical operational tool. The chelated copper formulation was introduced to the river through a diffuser boom, along with a non-toxic red dye, so its distribution and progress down the waterway could be monitored.

Post-treatment monitoring of the test site to determine effectiveness and impacts will continue for at least three months. Biosecurity New Zealand expects to receive NIWA’s report on the trial in June, and hopes to announce the results shortly after. Any practical control tool will still be some months away.

The trial is not expected to lead to the eradication of didymo from New Zealand. The formulation is intended as a control tool to help manage didymo blooms to low levels, which would greatly serve to reduce the negative impacts of the alga.

Summer didymo awareness campaign

Biosecurity New Zealand’s summer Check, Clean, Dry campaign is winding down. So far there has been very positive feedback from our partners, Regional Councils, Fish and Game and DOC. Their staff have enthusiastically been using the collateral produced as part of the summer campaign.

The summer campaign demonstrated a change in approach to biosecurity social marketing, based on social marketing best practice (as adopted by Land Transport New Zealand, Ministry of Health campaigns on smoking and mental illness discrimination, and SPARC’s ‘Push Play’), and draws upon in-depth formative research conducted with high-risk waterways users.

The campaign featured a range of promotional materials, including trigger spray bottles, information packs (pamphlet, sticker, and pen), sunscreen blisters, jelly beans, posters and river signage. These are designed to help motivate people to Check, Clean, Dry this summer.

Biosecurity staff have also been busy at the inter-island ferries, where people travelling between islands, (especially water-users), were also given the Check, Clean, Dry message. Staff at Picton and Wellington terminals handed out information to vehicle and foot passengers, paying particular attention to travellers with boats, fishing gear, kayaks and other aquatic equipment.

To complement this work, Biosecurity New Zealand made available a small community fund, which has been accessed by regional councils to develop local Check, Clean, Dry initiatives. In some areas regional councils worked with other partners to design summer programmes. Encouraging reports from these programmes are starting to come in, and will be kept in mind when designing programmes in the future.

Biosecurity New Zealand has also produced a set of event materials, which includes a Check, Clean Dry-branded tent, tear-drop flags, and pull-up banners showing the latest campaign material. Biosecurity New Zealand will be using these to target visitors at several water-based events around the country, including the Auckland Boat Show and Maadi Cup rowing regatta. These materials are also available to any stakeholder organisations attending events and spreading the Check, Clean Dry message.

A formal assessment of the summer campaign’s effectiveness will be conducted when it is completed. These results will help us to plan our future approach for next summer and beyond.

Update on cleaning porous items

Research has demonstrated unequivocally that didymo cells are knocked dead after only one minute in contact with numerous decontamination solutions, such as a simple 5% dishwashing liquid. There has been quite a lot of discussion around how to ensure the one-minute contact time is achieved using various application methods on various items. For non-porous items, such as fishing buckets, boat exteriors, tyres or trailers, spraying is effective and convenient for achieving the one-minute goal. But what about porous items such as sand shoes, clothing, buoyancy aids, anchor ropes, tramping boots and waders? Cleaning porous items presents a challenge because it’s difficult to determine exactly how long it will take for the cleaning solution to soak completely in to all the nooks and crannies of the porous item. It’s up to the user to ensure that the total treatment time includes whatever extra time it takes for the cleaning solution to fully penetrate the item.

Whether you apply the solution by spraying the item or submersing it in a bucket is up to you, as long as you can ensure that the solution has penetrated right through any porous item. Each item is different, so you need to use your discretion as to the most appropriate application method.

The two key points to note about porous items are that:

1. the decontamination solution must be applied such that it thoroughly soaks all areas of the item, and
2. the one-minute decontamination time starts AFTER the item is completely soaked by the solution.

Felt-soled waders

Felt-soled waders are a great example of the challenges faced when decontaminating water-absorbent items. Felt soles are thick and extremely dense and make ideal traps for didymo cells, which can be forced deep within the soles when walking in affected waterways.

The felt is dense and retains moisture (and live didymo cells) for long periods, is very slow to dry out and feels dry on the surface even when moisture is still trapped inside. In practical terms, this means it can take several weeks before these waders can safely be used in another catchment if drying is the only decontamination method used.

To make matters worse, decontamination solutions do not passively soak quickly into the dense felt, and it is difficult to ensure that felt-soled waders have been soaked long enough to allow complete penetration of the cleaning solution throughout the sole.

Cleaning methods have been developed specifically for felt-soled waders and have been shown to be effective. These were included in our December update, but are included again as a reminder of their special requirements. If these decontamination options are not practical for your purposes, it is recommended that you use rubber-soled waders or restrict the use of your felt-soled waders to one catchment.

To decontaminate 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 at least 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 methods for decontaminating felt soles can also be applied to other dense, absorbent materials.

Operations update

It is pleasing to note that many of our partners are now using sampling and analysis protocols developed by Biosecurity New Zealand and NIWA. It is important that we have this level of consistency as more partners become involved with sampling as an extension of their environment monitoring and surveillance programmes. This will become more important in the future, as Biosecurity New Zealand is developing a surveillance database with the intention of partners being able to input their own surveillance data for all to access. Note that we are making sampling kits available to those regions that have surveillance programmes in place.

The long-term management programme has been presented to the partner group and is to be further discussed at regional meetings over the next few months.

We will also be undertaking a North Island response simulation within the next two months to challenge fully our North Island incursion response plan.

The second summer delimiting survey has been completed, as have a number of partner sampling programmes. The good news is that all 67 high-risk rivers sampled in the North Island were negative. New rivers identified as positive in 2007 include:

• Upper Mararoa
• Greenstone
• Kawarau
• Haast
• Motueka
• Manuherikia
• Tekapo
• Owan
• Matiri
• Wairaurahiri

The next high-risk delimiting survey will be undertaken in April 2007.

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