B. nodosa got very black sunken spots but complete leaves never dried up. Cats and Laelia seemed to be mostly unaffected. BC and BLC plants had some sunken black spots, but some only showed very mild brown spotting. Dens seemed to be unaffected, except for aggregatum which had brown sunken spots and lost most of its leaves. I just happen to have other fungal problems on these at the same time.
Experts can be wrong.
I am not convinced the above treatment will cure a plant, but I am fairly sure it prevents the spread of the disease. I have received a number of emails about Microfungus but none of them have ever indicated that they cured the disease. It is either a fungus or it's not. In any event, in the lay persons world, people call this disease, microfungus. The above descriptions of the symtoms seem to be fairly consistent when I talk to other growers.