They are controlled best by using resistant hybrids and a balanced fertility program. Since major corn pathogens can overwinter in Pennsylvania, tillage and rotation are common cultural practices for reducing sources of disease-causing organisms, particularly if disease was a problem the previous year. Delayed harvest leads to greater field losses. Harvest dates should be determined by crop maturity, not by the calendar. Disease prevention or control with fungicides other than seed treatments usually is not economical and should be considered only on an individual basis.
Lesions first appear on the lower leaves, progressing to the upper leaves over time.
A few years ago, the incidence and severity of this disease increased with the occurrence of a new race of the pathogen. Higher levels of genetic resistance to the new race have been incorporated into many hybrids, so disease-caused losses have been limited in the last several years. Potentially, however, this disease can result in yield losses. Bacterial leaf blight Prominent in many areas of Pennsylvania, the organism causing the disease overwinters in the corn flea beetle and is transmitted by this insect. If this sum is greater than 85, severe levels of bacterial leaf blight may be expected on highly susceptible hybrids.