The most common symptom of leaf scald is a white line about 1–2 mm wide (also called a pencil line) on the leaf. This line extends from the midrib to the leaf margin running parallel to the veins. A diffuse yellow border of varying widths runs parallel to the pencil line. The pencil line may have areas of reddish discoloration along part of its length. As the disease progresses, brown, dead tissue (necrosis) develops from the leaf tip or leaf margin and eventually extends the entire leaf. Leaves look burned and curl inward, giving them a scalded appearance–hence the disease's name. Ultimately, the entire plant dies.

Ref:USDA