Plant Health Initiative

Cercospora Leaf Blight - Scouting

Look for bronzed leaves at the beginning of seed set and into maturity. Photo credit: North Carolina State University

Scout for Cercospora leaf blight during late-season field scouting. Look for a purplish-bronze discoloration of the canopy. Only the top leaves are affected. As the plants mature, the leaves begin to look leathery. In susceptible cultivars, the entire leaf surface may have this appearance.

Cercospora can be mistaken for sunburn, sudden death syndrome (Fusarium verguliforme), pod and stem blight (a disease caused by Diaporthe and Phomopsis fungi), or even early senescence.

If you look closely at individual leaves, you'll see reddish-purple spots that vary in size. Large brown patches develop as the spots merge. The fungus itself can't be seen without a microscrope.

At maturity, check the seed for purple discoloration, which is the seed phase of the disease.