Brown Spot [Alternata Blight] (on leaves) or Black Pit (on tubers), is caused by Alternaria alternata and often confused with early blight (Alternaria solani). Infection causes spotting of stems and leaves throughout the season, is often observed on newly emerged leaves near the top of the plant canopy, and heavy infection may cause premature leaf drop.
Early symptoms on leaves are small, round, dark spots.
Individual or coalesced lesions develop concentric rings as they enlarge.
Coalesced lesions can form larger necrotic areas with dark brown margins which can then cause leaves to dry up and drop off prematurely.