Cercospora Leaf spot (Gray leaf spot)Caused by: Cercospora zeae-maydis
Problem Category: Fungal Disease
Symptoms: Small necrotic spots with chlorotic halos on leaves which expand to rectangular lesions 1-6 cm in length and 2-4 mm wide; as the lesions mature they turn tan in color and finally gray; lesions have sharp, parallel edges and are opaque; disease can develop quickly causing complete blighting of leaves and plant death.
Comments: Disease emergence is favored in areas where a corn crop is followed by more corn with no rotastion; severity and incidence of disease is likely die to continuous corn culture with minimum tillage and the use of susceptible hybrids in in the midwestern corn belt of the USA; prolonged periods of foggy or cloudy weather can cause severe Cercopora epidemics.
Management: Plant corn hybrids with resistance to the disease; crop rotation and plowing debris into soil may reduce levels of inoculum in the soil but may not provide control in areas where the disease is prevalent; foliar fungicides may be economically viable for some high yeilding susceptible hybrids.