Question
Wayne, I have a dendrobium "Cleopatra" that is now blooming with beautiful purple blooms. the plant appears healthy except a few days ago two leaves (the 2nd & 3rd) from the bottom of the spike developed a large black spot on them, and the leaves have turned yellow and are drying up. The spots are thick and hard, while the rest of the leaf has become thin. I have not been able to find this problem covered anywhere. Can you tell me what is going on, and what, if anything, I can do. Thanks. BJ

Answer
My guess is that you have a fungus producing the leaf spot.  To prevent this from potentially spreading, find a fungicide at your nearest garden center.  My preference is to use a copper salt spray.  This will not "cure" the fungus infected leaves but could protect against spread of the fungus to healthy tissue.  Spray the top and bottom of each leaf and repeat at two week intervals for a month.

You didn't mention how long you have had the plant and whether you keep it on the wet or dry side.  At this point, I recommend that you grow it a bit drier as that can also reduce the environment for spread of the fungus.