The disease symptoms start with small spots with discoloration on the lower leaves of the plants. The infection starts from lower leaves and spreads rapidly by wind or rain splash.

The leaf spots will turn tan to dark brown. Severely affected leaves have small lesions merge and leaves turn yellow. Blighting of the leaves may follow.

Wet and humid conditions from mid-summer and through the fall favor development of the disease. Infected leaves from the previous year are the main source of inoculum.

The pathogen can be identified by the characteristic conidia.