It may kill the spores that it contacts, but it may not contact any that have fallen down deep between the leaves. It will also not kill the body of the fungus inside the leaves if there is a pre-existing infection that hasn't yet produced spores on the outside. Too strong a solution and/or too long a soak can damage the plants. I haven't tested this so maybe someone who does this routinely can comment. I have tested dropping diluted bleach on a pustule and it appeared to work but another pustule later erupted right beside it.
