Signs and symptoms: It can have medium (0.5 to 2 in.) rectangular lesions. The disease can be red or brown and later turn grey. The lesions are restricted by leaf veins. It begins on lower leaves and works its way up the canopy.
Inoculum source: Infested corn residue from prior year(s). It is spread by wind or splashing water.
When to start scouting? Normally seen starting two weeks prior to tassel.
Conditions it can be found in? Hot and humid (80° F and above) and cloudy. Wet, humid weather that keeps the leaves wet for long periods.
Management strategies: Yield impact depends on when it establishes and how quickly it spreads. If the infestation occurs at or around the VT growth stage, it will likely impact yield. Conversely, if the infestation occurs several weeks after VT, the yield impact will be negligible. If inoculum is present, rotate to a non-host crop. Reduce corn residue on the soil surface. Select for a hybrid with a good GLS rating.