Northern corn leaf blight is a disease we're hearing a lot about but I have yet to see it in our area.  Most have been mistakingly calling the unknown bacterial disease shown above northern corn leaf blight, but there's truly a difference as you see these photos.  Compared to gray leaf spot, northern corn leaf blight will be more cigar-shaped instead of forming a rectangle.  As this photo taken from the Mead, NE area shows, lesions are often forming in close proximity to each other on the leaves in Nebraska right now.  This disease is one to watch as it has been expanding on certain hybrids in some fields, particularly in eastern, Nebraska.  However, I still haven't seen it in our area and haven't received any confirmations of it being found in our area.  