I understand that you are doing what you have been told is the right thing to do. I commend you for that.
I have been in science a long time and when I read something that just does not seem reasonable, I look for another explanation. I have been posting about dydimo for many years, and in all the posts, I have been the sceptic and on the side of those who did not believe that replacing felt soled boots would slow down dydimo or any other invasive.
There are too many ways for invasives to be carried other than in felt and I am not referring to animal vectors of transfer.
As I said before, there is no single chemical that is safe for use on waders and boots that will kill all invasives. That is a big problem and so the most common recommended method is to wash the wading equipment with fresh water. Washing decreases the amount of invasive transfer. But dydimo, new zealand mud snails, and whirling disease myxospores can multiply asexually. Only a single live organism is needed to infect a river system. Clearly, banning felt soled wading boots is a futile effort.
Secondly, it just did not make any sense to me why all of a sudden, dydimo, an organism that had been in North America for centuries, should suddenly go wild. There are two main reasons for the explosion of a population. The first is a change in the organism, and the second is a change in the environment.
Was there a change in the organism itself so that it changed genetically to a more virulent form? Close examination showed that dydimo was the same organism as it was hundreds of years ago.
If it was not a change in the organism, then was there a change in the habitat? We know that dydimo lives in water. They tested the water where dydimo blooms occurred and found that a low concentration of phosphorus caused dydimo to grow filaments and create the mats of vegetation that is "rock snot". Add phosphorus and the blooms disappear.
How about that? The blooms are not caused by evil fly fishers with felt soled boots spreading dydimo. The dydimo was already there waiting for low phosphorus to stimulate it.
Why did the water chemistry change? It changed because phosphates in detergents and in lawn fertilizer began to cause algae blooms in lakes and rivers and so they were phased out. Now we have low phosphate rivers and dydimo blooms instead.
Laws to reduce phosphorus | Washington Department of Ecology
16 states ban phosphate-laden dishwasher soap
Phosphorous Lawn Fertilizer - Ban on Phosphorous Fertilizer in Maryland - The Daily Green