However, the disease is most serious in warm regions or during periods of warm, humid weather. Symptoms of frogeye leaf spot occur primarily on leaves although the causal fungus may also infect stems, pods and seeds. Lesions are small, circular to somewhat irregular spots that develop on the upper leaf surfaces. Initially the spots are dark and water soaked in appearance. As the lesions age, the center of the lesion becomes light brown to light gray in color.
Older lesions have a light center with a darker red to purple-brown border.
Lesions may merge to kill larger areas of the leaf surface. Heavily spotted leaves may wither and drop prematurely. Stem lesions can develop later in the season. Young stem lesions are reddish brown with a narrow, dark margin. As the stem lesions age, the centers become brown to gray in color.