A symptom of disease
characterized by a limited necrotic or discoloured area, as on
leaves, flowers, and stems.
A "spot" is a general term used to indicate a
relatively small, distinct lesion, with well-definite borders
due to any of a variety of disease-causing organisms like
Viruses, Bacteria and Fungi.
Most times, we indicate the plant organ affected when describing
a plant disease symptom. For example, if the spot is on leaves,
it is called a "leaf spot". If the spots are on fruit, it is
naturally a "fruit spot".