Didymo Cleaning

Decontamination of paddling gear without damaging it

MAF Biosecurity’s Didymo decontamination requirements (see below) have produced some concerns about the potential for some of the suggested cleaning methods to damage often expensive equipment. Some advice on what substances to use for decontamination of such materials, without causing damage, but still remain effective against Didymo follows.

This advice is based on information about fabrics and foam from the Design Team at Macpac who test materials used in Macpac’s extensive range of outdoor gear, info from other manufacturer’s websites and observations from myself and others who have been paddling for a while. It is intended to help you decontaminate your gear without harming it, while still being effective against Didymo. While no absolute guarantee against harming your equipment can be offered, this is the best advice I can find and is the most current info available to me. If you find any new info, please contact me and I can forward it on.

Keep an eye on MAF’s Didymo page and the NZRCA’s website for any updates regarding Didymo. I’ll try to put any useful info/links that come my notice here too.

It is expected that this cleaning info will be useful to all river users who have any concerns about decontamination procedures potentially harming their gear.

N.B. Where you see “fresh water” mentioned in this advice, it means water from a town supply or well that is drained to a septic tank, soak pit or treated drain system and does not run directly into a waterway - not water from the nearest stream! Water from places like formal camp-grounds (eg: Riverview or Kiwipark in Murchison) or other such accommodation you are using while away, or from your own home is what is meant.

MAF’s approved decontamination system

Check: 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.
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 200ml, a five percent solution is 500 ml (two large cups), with water added to make 10 litres.
Dry: If cleaning is not practical (i.e. livestock), after the item is completely dry to touch, wait an additional 48 hours before contact or use in any other waterway.

Cleaning with minimal risk of damage:

Bouyancy aids:

Salt can be damaging to b/a foam. The crystals grow as salt-water dries, damage the foam cells and cause the foam to harden and eventually become crumbly. It loses its bouyancy as a result.
Coated nylon fabrics commonly used as b/a shells can also be damaged by salt. The salt crystals expand between the fibres, and between the fibres and the coating, leading to de-lamination and break-down of the fabric.
Nylon webbing is similarly damaged by salt. It can become stiffened after repeated exposure to salt and lose its strength and suppleness.
Bleach and chlorine are even worse for all these materials.
Household dish-washing detergents, especially “green” versions such as Simply Green are unlikely to cause any damage to these materials.
While rinsing your rescue gear (slings, ropes etc) thoroughly in fresh water when you get home after a trip is advisable, having them go through multiple treatments with this sort of stuff should not cause harm during the course of a multi-catchment trip. B/a foam should not be damaged by this stuff either and there is probably no harm if the foam happens to be almost perpetually detergent-logged.

Dry-tops and cags:

Membrane fabrics, like Gore-Tex, can be washed in a saline solution. However, they suffer a similar fate to coated nylons if they are not subsequently rinsed in fresh water. The salt crystals grow as the water dries and cause the membrane to rupture. Makers of Gore-Tex garments intended for sea-kayaking recommend rinsing salt-encrusted garments in salt-water during a trip if fresh-water is not available, but also say you should rinse in fresh water as soon as it becomes available. So, best advice if you are using salt solutions to decontaminate is to not let the salt water dry on your garment and subsequently rinse in fresh water
Coated nylons are mentioned above.
Don’t ever use bleach to clean a membrane fabric garment in particular. Avoid contact with chlorine too.
Household dish-washing detergent is again the most gear-friendly choice and should not cause damage with repeated dunkings on a long trip.
Rinse thoroughly in fresh water when you get home after a long trip.
Your dry-top may need more frequent applications of DWR treatment.

Insulation garments:

Neoprene has been used in salt-water for years of course and tolerates all sorts of abuse, including pool-type chlorine concentrations. It still likes a fresh-water rinse of course or it becomes stiff over time. Don’t use bleach.
Most insulation fabrics (polypro, wool, polyester, nylon and blends of these) should not be damaged either by salt or dish-wash. Most of them don’t like bleach.
For the sake of your skin and general comfort, you will probably want to rinse your garments in fresh water after treatment if you have no choice but to re-use them during a multi-catchment trip if they have become wet.

Boats:

Your boat should handle pretty much any treatment you throw at it. Remember it has lots of nooks and crannies, many have grab-loops made of nylon tape or similar and water can be absorbed into the foam pillars and hip-pads etc.
The easiest way to treat a boat seems to be to get 5-10 litres of dish-wash solution (bigger boat, more solution), tip it in, put a cockpit cover (or spray deck with tied-up waist) on and swish the solution thoroughly around in the boat for at least a minute. There seems to be no reason to prevent you from biffing your gear in the boat when you do this, thus treating the whole lot at once, but be aware that it all needs to be decontaminated properly and this method may not always be the most effective.
Deflate your air-bags first so they get treatment too.
Don’t forget to decontaminate the outside of your boat as well.
Leave the air-bags hanging out so the inside of your boat can dry more easily. Leave the boat on its edge so any remaining water trapped under the foam pillars can drain away and be mopped out.

Overall considerations:

Best practice advice from MAF is to treat every waterway you leave as contaminated and every one you enter as clean. This means that in order to avoid transferring Didymo from one river to another you should decontaminate your gear every time you move from one river to the next, regardless of what you think its Didymo status is. This is a conservative policy I know, but is the best way (at least until we all know more) to limit the spread of Didymo.
As a minimum for day trips, you should decontaminate your boat near the take-out. As long as your gear is contained in a vehicle (and not dripping all over the place from being stuffed in your boat on your roof rack on the way home) you can leave gear decontamination until you get home.
Multi-river trips will obviously require a bit more thought and work to decontaminate between sites, but MAF has gone to some lengths to devise methods that are easy for us to use. In conjunction with advice here, you should have no problem adhering to their requirements.

We all know what we need to do now, so there is no excuse for being slack. Let’s get out there, keep having fun on the water and be really anally-retentive about cleaning our gear so we don’t spread Didymo.

Happy paddling and cleaning,

Ian Gill-Fox.
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