how do i remove black spot from orchids?

Answer 1

According to the sites I found, the black spots are a sign of excessive moisture.

"Continued dampness in the pot will break down the soil and exclude air, killing the active plant life bacteria. This encourages the accumulation of toxic substances and the growth such as those which produce the parasitic fungi known as 'blight' and 'black spot' The foliage may blacken and wilt and black blotches may appear on the leaves. These conditions are very commonly seen along the coast where they attack crops of tomatoes and potatoes. These diseases are in no way connected with the white fleck or mosaic disease. The fungoid diseases are much more fatal, but, fortunately, they are much more easily cured by correcting the conditions (i.e., surplus of water) which have brought them about."

From:

http://www.bribieislandorchidsociety.com/plant_info.htm

Answer 2

i think mother earth may have the answer to your question --- ill post the link below