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SofthackleJuly 24th, 2007, 7:53 pm
Site Editor
Wellsville, NY

Posts: 540
For those of you that have not yet become aware of this stuff, here's some important information. We that love to fly fish, study insects and tie flies can be severely affected by this invasive species. I received this info today from TU.

An invasive algae, commonly called rock snot, has been found in the Upper Connecticut River and in Vermont's White River. The Vermont and New Hampshire TU Councils and chapters need your help to stop the spread of didymo before it devastates wild trout populations.

Didymo does not present a health hazard to humans. However its impact on native and wild trout populations has been severe in New Zealand, Quebec and other areas. The algae, which thrives in cool water temperatures, attaches itself to the gravel and rocks at the bottom of the river bed. When the algae blooms, it forms massive mats that coat the gravel and rocks (reports of 4 to 5 inch thick mats are common). These mats form a barrier for native organisms (caddis, mayflies and stoneflies) that result in their decline. Studies suggest that young, wild trout populations are severely affected.

In addition, didymo is easy to spread. Each cell is very small, so they absorb easily into clothing, wading boots, and sandals as well as stick to hard surfaces like tubes, kayaks, and fishing gear. If these items are not cleaned and dried completely, the algae will live (one report had didymo surviving for 8 months on felt sole boots stored in a garage) and can be spread the next time the item is used.

1.) Soak all clothing, wading boots, sandals, etc in hot, soapy water for 30 minutes.

2.) Wash all hard surfaces like tubes, kayaks, and fishing gear with hot, soapy water as well.

3.) A 5% detergent solution is effective. Use 3/4 cups of any detergent (dish soap, antiseptic hand soap, or laundry detergent) per gallon of hot tap water to kill the algae.

4.) Learn more about didymo algae at For additional information about efforts in Vermont to address the problem contact Mary Russ, Executive Director, White River Partnership at 802-767-4600

Hope this brings our awareness level up!


"I have the highest respect for the skilled wet-fly fisherman, as he has mastered an art of very great difficulty." Edward R. Hewitt

Flymphs, Soft-hackles and Spiders:
KonchuJuly 25th, 2007, 9:28 pm
Site Editor

Posts: 496

What is the primary source for this report?
GONZOJuly 25th, 2007, 10:12 pm
Site Editor
"Bear Swamp," PA

Posts: 1681
Thanks for posting the rock snot info, Mark. There are so many invasive species threatening our waters these days that it is easy to surrender to feeling helpless and overwhelmed by it all. That is until one of them shows up in your favorite stream, then in addition to feeling helpless and overwhelmed, you feel damned angry.
SofthackleJuly 26th, 2007, 6:08 am
Site Editor
Wellsville, NY

Posts: 540
Hi, the above information was received in an e-mail from TU, however, there are other online sources regarding the discovery of this invasive species in the north eastern US. Many rivers in the west are already fighting this stuff, and there is little that can be done to get rid of it. The best thing to do is prevent the spread of it. Here's some places to look for more info on this.


Hope this helps,
"I have the highest respect for the skilled wet-fly fisherman, as he has mastered an art of very great difficulty." Edward R. Hewitt

Flymphs, Soft-hackles and Spiders:
KonchuJune 8th, 2011, 9:19 am
Site Editor

Posts: 496
Here's some recent info on Didymo, from the US National Science Foundation. The study they discuss was done in Rapid Creek, western South Dakota.
Shawnny3June 8th, 2011, 10:41 am
Pleasant Gap, PA

Posts: 1197
Sadder still, there is no insidious villain to be angry at in cases like this. Some invasive species are intentionally introduced or the result of other types of human stupidity, but ones like this are just the natural consequence of ease of travel. Maybe there is an upside to really expensive gasoline. Too bad we all can't just fish our local streams.

Bottom line: Unless EVERYONE is well educated and very careful, problems like this will continue to spread. Thank you for putting it in the fore of our consciousness, Mark.

Jewelry-Quality Artistic Salmon Flies, by Shawn Davis
SofthackleJune 8th, 2011, 12:54 pm
Site Editor
Wellsville, NY

Posts: 540
Recently, I read somewhere, that Formula 409 works to kill the cells on boots and felt soles. It easy to use from it's spray bottle and does not do as much damage as bleach.

"I have the highest respect for the skilled wet-fly fisherman, as he has mastered an art of very great difficulty." Edward R. Hewitt

Flymphs, Soft-hackles and Spiders:
Jmd123June 8th, 2011, 1:17 pm
Oscoda, MI

Posts: 2385
Has anyone heard of any reports of Didymo from Michigan? I have not, so if anyone else has please let me know, as I do have felt-soled wading shoes! And Mark, that's a great tip, especially as 409 is made as a carpet cleaning version which one would hope is designed not to damage fabrics such as felt. Hard to give up the felt when I have done the "slick-rock dance" before, though the streams that I fish mostly have sand and silt bottoms with occasional gravel stretches and not so many rocks.

Shawn makes a good point about fishing local streams, as travelling between various watersheds is believed to be part of the problem in the spread of aquatic nuisance species. I know not everyone has the option of doing so, especially in today's world where you have to live where the work is, but if one CAN live in an area where you don't have to travel far and wide to chase trout, it helps in a lot of ways (like saving $$$ on our currently outrageous gas prices, well over $4/gallon here in MI). I am most fortunate to be in this situation (hey, this IS where my work is, and I might be teaching biology this fall at a local community college to boot) and I wish all of my fellow troutnuts could do the same.

No matter how big the one you just caught is, there's always a bigger one out there somewhere...
MartinlfJuly 15th, 2011, 10:15 am
Palmyra PA

Posts: 2936
Mark, Jonathon,

Formula 409 is not generally effective as a spray on treatment.


I just did a treatment after returning from the Delaware and used one of those huge ziplock bags to shake and soak my boots and net in, using very hot water and Dawn detergent. My waders got a thorough hose washing while hanging up on the clothes line and will dry for a couple of weeks while I use my back up pair to fish local streams. I understand that flies and fly lines can harbor the stuff, and they should be cleaned, or dried for several weeks too. An alternative treatment is freezing potentially affected gear, and this may be best for felt sole wading boots. I bit the bullet and bought rubber soled Simms boots a while back due to the didymo threat. With the tungsten star cleats they work very well--no slick rock dance.

For more on invasives:
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell
GONZOJuly 15th, 2011, 12:30 pm
Site Editor
"Bear Swamp," PA

Posts: 1681
Thanks for the update, Louis. I've activated the links in your post, and here are the recommendations of the NZ report on Didymo decontamination (Kilroy 2005, revised 2006):
...recommendations for decontaminating materials that may have come
into contact with D. geminata are:
o Soak and scrub in a 5% (v/v) solution of either salt, nappy cleaner, household
antiseptics (chlorhexidine or chloroxylenol based) or detergent for about 1 minute.
o Or, soak and scrub in a 2% solution of household bleach for 1 min.
o Or, immerse contaminated items in hot water for 2 min, to a final temperature of at
least 60 C.
o After swimming in an affected waterway, allow hair to dry completely, then shampoo
for at least 1 minute, and rinse thoroughly using warm to hot water.
o For large items of equipment, desiccate completely by drying for an extended period
of time (e.g., 48 hours) after all parts of the item (and therefore algal mats on or
within it) appear to be dry.

BTW, I have been using sticky-rubber-soled wading boots for more than a decade and have no complaints. (The soles last much longer than my felts ever did.) When the wading is especially slick, I carry a pair of slip-on wading chains.
SofthackleJuly 15th, 2011, 12:32 pm
Site Editor
Wellsville, NY

Posts: 540
I have been told that cleaning with hot soap (Like Dawn) and water would kill Didymo. If that's the case, why wouldn't 409 work as well. It does contain antibacterial qualities, and it is less corrosive than bleach. I'm not saying the report is wrong, however, I think we need to consider 409 as a possible alternative. A good spray down with with 100% 409, leaving it on, then washing with hot water may well accomplish the job. Don't know what to think. I also thought there was another commercially available spray for Didymo and the like. I don't remember the name, however. Thanks for the info!

"I have the highest respect for the skilled wet-fly fisherman, as he has mastered an art of very great difficulty." Edward R. Hewitt

Flymphs, Soft-hackles and Spiders:
Jmd123July 15th, 2011, 8:58 pm
Oscoda, MI

Posts: 2385
How about an algacide, since it's an alga? Anybody know anything about this?

No matter how big the one you just caught is, there's always a bigger one out there somewhere...
MartinlfJuly 18th, 2011, 7:43 pm
Palmyra PA

Posts: 2936
Thanks, Gonzo! ;>

Mark, I'll bet if Formula 409 is used the right way, with hot enough water, for the right amount of time, it possibly could work. What the article made clear is that the original application was for NZ Mud Snails and it was not a quick spray it on wash it off procedure. That's what I was trying to point out. That kind of cleaning simply won't work well for any invasive--especially on felt soles.
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell

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