University of Illinois

No. 16/July 10, 1998

Foliar Diseases of Corn

The wet weather conditions also favor corn leaf blights, especially gray leaf spot (GLS). The gray leaf spot fungus requires wet leaves for infection and colonization of the tissues. This fungus produces spores that can remain on the leaf surface up to 14 days without infecting, providing the humidity levels remain above about 60 percent. Infection occurs when humidity levels reach almost saturation (around 90 percent), and the disease cycle can be repeated every 10 to 14 days.

What about managing gray leaf spot? The following article by Paul Vincelli, Extension specialist at the University of Kentucky, offers an excellent summary of GLS management. Although it is directed toward producers in Kentucky, much information is applicable to Illinois producers as well. The basics of disease management that Paul discusses are easily adaptable to those areas of Illinois where GLS can be expected in most years (western and southeastern Illinois).

H. Walker Kirby (, Extension Plant Pathology, (217)333-8414