Conditions Favoring
Disease Development
The NCLB fungus survives through the winter on
infected corn residue at the soil surface. As temperatures
rise in the spring and early summer, the fungus produces
spores on residue, and then the spores are splashed or
wind-blown onto leaves of the new corn crop.
Infection occurs during periods of moderate (64° to
81°F), wet, and humid weather. The fungus requires six
to 18 hours of water on the leaf surface to cause infection.
Therefore, symptoms are commonly observed
following long periods of heavy dew and overcast days,
and in bottomlands or fields adjacent to woods where
humidity will be higher and dew will persist longer into the
morning. In Indiana, symptoms are frequently observed
late in the growing season, when days become cooler.