If you are moving items between waterways, you must Check, Clean, Dry.
CHECK: Before you leave a river or lake, check items and leave debris at site. If you find any later, treat and put in rubbish. Do not wash down drains.
CLEAN: There are several ways to kill didymo. Choose the most practical treatment for your situation which will not adversely affect your gear.
* Non-absorbent items
* Detergent: soak or spray all surfaces for at least one minute in 5% dishwashing detergent or nappy cleaner (two large cups or 500 mls with water added to make 10 litres); OR
* Bleach: soak or spray all surfaces for at least one minute in 2% household bleach (one small cup or 200 mls with water added to make 10 litres); OR
* Hot water: soak for at least one minute in very hot
water kept above 60 °C (hotter than most tap water) or for at least 20 minutes in hot water kept above 45 °C (uncomfortable to touch).
* Absorbent items require longer soaking times to allow thorough saturation. For example, felt-soled waders require:
* Hot water: soak for at least 40 minutes in hot water kept above 45 °C; OR
* Hot water plus detergent: soak for 30 minutes in hot water kept above 45 °C containing 5% dishwashing detergent or nappy cleaner; OR
* Freezing any item until solid will also kill didymo.
DRY: Drying will kill didymo, but slightly moist didymo can survive for months. To ensure didymo cells are dead by drying, the item must be completely dry to the touch, inside and out, then left dry for at least another 48 hours before use.
If cleaning or drying is not practical, restrict equipment to a single waterway.
NOTE: The thicker and denser the absorbent material, the better it will be at holding moisture (and live cells), the slower it will be to dry out and the more difficult it will be to soak completely with cleaning solutions.
When cleaning gear, we recommend that you:
* Soak absorbent items for longer than specified to ensure thorough saturation of the material with the cleaning agent
* Follow manufacturer's safety instructions when using cleaning products
* Dispose of cleaning waste well away from waterways.
Cleaning options:
The standard decontamination treatments are included in the Check Clean Dry message above. Further information is available in a table comparing the effectiveness of methods and products tested on didymo survival, published in the Didymo Survival Study Report. This table includes information on using reduced concentrations of decontamination products for longer soaking times to suit high volume commercial users who wish to soak gear overnight at less expense to themselves, their business and the environment.
* Table of Didymo Survival Results - May 07
<http://www.biosecurity.govt.nz/files/pests-diseases/plants/didymo/didymo-survival-results-table-may-07.pdf>
(186 Kb)
Unless otherwise stated, all dilutions are given as volume of cleaning product/volume of total water (v/v). For example, a 5% solution is made by mixing 50 ml of product with water added to make 1000 mls (1 litre) total.
The table below describes in more depth how to clean specific items. Unless stated otherwise (such as for felt-soled waders and boots), all of the decontamination options are effective on all items, provided that absorbent items are thoroughly soaked.
Felt-soled waders and boots
Fishing footwear containing absorbent material, such as felt-soled waders and boots, poses a high risk of didymo transfer-these items are likely to come into direct physical contact with didymo cells (e.g., stepping on or brushing against algal mats), and the moisture retained in these goods helps cell survival.
Choose one of the following treatments specific to felt-soled waders and boots:
Hot water: If hot water alone is used, careful attention is needed to ensure the temperature of the water is maintained at no less that 45 °C for 40 minutes to ensure the interior of the felt reaches a sufficient temperature to kill all cells;
OR
Hot water and detergent: The entire felt sole and boot needs to be completely immersed for 30 minutes in hot tap water kept above 45 °C (uncomfortably hot to touch) containing 5% dishwashing detergent or nappy cleaner;
OR
Freeze until solid: The time required until the boot is frozen solid will vary depending upon the grade of material, how much moisture it contains and the efficiency of the freezer. Freezing overnight should work in most instances.
Drying: Relying on ambient drying as a stand-alone treatment for decontaminating highly absorbent risk goods such as felt-soled waders and boots is not recommended in situations where use between waterways is frequent (daily, weekly or even monthly). Drying should only be relied upon as a decontamination treatment if great care is taken to actively and completely dry the felt (such as by using a heat source where temperatures around the felt are assured of reaching 30 °C). Once the felt appears dry, complete dryness must be confirmed by a tactile inspection of the felt pile to the base of the fibres. Once completely dry, items must remain dry for at least 48 hours before use in another waterway.
These instructions for decontaminating felt soled waders and boots can be used for other absorbent materials.
If you do not want to decontaminate your gear, you should restrict use to a single waterway.
Rich Kirn
Fisheries Biologist
Vermont Fish and Wildlife Department
rich.kirn@state.vt.us