Cattleya walkeriana with black spots on leaves

[Roberta]

If this were my plant, I would cut away the black area with a single-use single edged razor blade, and then dust the cut edge with cinnamon. If it is a fungal infection, it is probably local - for the moment. You don't want that infection to get into the rest of the plant, and cutting away the bad part (go a little into the clean tissue to be sure of getting it all) may well stop it in its tracks.