Cercospora Leaf Blight and Purple Seed Stain

Cercospora kikuchii

Cercospora leaf blight is fairly common and widespread in NY, though it can be difficult to distinguish from sun scald.  Symptoms often appear during reproductive stages first as light purple areas on leaves in the upper canopy, which may expand and turn a darker purple to almost leathery brown, and finally necrotic leaves will drop prematurely.  Defoliation will occur first in upper leaves, and then move down the canopy.  Severe epidemics are rare in NY, and fungicides are not recommended for management. 

The primary concern of Cercospora leaf blight to NY growers is the development of purple seed stain resulting from the infection. 

Discolored seeds, if at high enough levels, can result in rejection, especially for edible soybean varieties.