The term “leaf spot" is a tricky one, as it is used by different people to mean different things. Simply being a spot on a leaf does not necessarily make it a leaf spot! Many definitions of leaf spots can be found in books, but in this course we have taken a very general view on leaf spot and consider it to be a spot on a leaf with a necrotic (dead) area within it.
Leaf spot on lettuce
Leaf spot on lettuce
The leaf spots on this lettuce are evenly spaced, have a clear edge to them, and are comprised of an inner zone (yellow) and an outer zone (brown). They are not associated with the leaf veins nor the leaf edge.
