Hello chopficaro,
First, You cant wash pathogens off of roots.
Second, Blocking light wont stop or reduce pathogens. Blocking light only stops algae. Algae isn't a pathogen, it's micro flora (a microscopic plant). Like any other plant it needs light energy to survive and grow, that's why blocking light stops algae. Algae doesn't harm plants. Not directly anyhow. It does consume the same
nutrients and dissolved oxygen the plants need. If theirs enough algae the plants may have to compete for nutrients and oxygen. So potentially, large amounts of algae could starve the plants. But algae isn't a pathogen and wont harm the plants directly.
Third, I'm still waiting for you to finish answering the rest of my questions in the other thread. You said you wanted to solve a puzzle. In order to put a puzzle together and solve it you need to have all the pieces first. That's why I asked the questions I did, to get the pieces of the puzzle I need to help you solve it. Without all the pieces of the puzzle I would just be making random guesses based on bits and pieces. Your the one with the puzzle pieces, and I can't help you solve the puzzle if you don't share the puzzle pieces with me.
If you don't want my help I would appreciate it if you just told me that so I'm not wasting my time trying to help you. If you don't want my help I won't bother replying to your threads anymore. We could both be happy. You won't have to be bothered by me, and I won't be wasting my time on you.