black spot

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various fungal or bacterial diseases of plants, resulting in small black spots on the leaves or on other parts.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A fungal disease among plants, particularly roses, that results in black spots on the leaves.
• noun A section of roadway that has been designated as being particularly accident-prone.
• noun A fictional judicial device among pirates, consisting of a black circle indicating condemnation.
• noun snooker The spot on a snooker table where the black ball is normally placed.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of several fungous diseases of plants that produce small black spots on the plant