Minor Leaf Spots (fungi - Alternaria sp., Cercospora sp., Rhizoctonia sp., Stemphyllium sp.): Two or more leaf spots may occur at the same time. Symptoms are varied, but generally these organisms cause circular concentric lesions similar to a target spot . These foliar diseases tend to be more prevalent at crop maturity and during periods of high humidity. Preventive control measures are most effective and include seed treatment, good management practices, and destruction of plant residue after harvest. Some varieties are more susceptible to late season leaf spot fungi.
