Greg Roth
Associate Professor
Penn State
January, 2003

Background

     I stopped by this cornfield near Mountoursville, Lycoming County one day a couple years ago with Extension Agent Tom Murphy. On one end of this field a 100 foot wide swath across the field showed a much reduced stand. (Click on the upper image at the right for a larger view) From a distance one might expect some sort of misapplication of a herbicide on the ends of the field. Closer inspection though showed that some of the larger plants had shredded lower leaves. Also, Tom pointed out that many smaller plants in the swath had fallen over and died at about the V5 stage of growth. (Click on the lower image at the right for a larger view) Apparently some event occurred during this period that shredded the leaves on some plants and knocked over and killed the plants in the rest of the field. You might suspect a hailstorm, except much of the rest of the field was undamaged. (Click on the image to the right for a larger view)

Diagnosis

     I had to rely on Tom for the solution to this one. Apparently a small tornado passed through this farm and cut across this field causing this localized damage. Tom got a call from the grower after it happened and visited the field previously. Tornado damage was also evident in the swath in the surrounding countryside.

     Localized wind and storm damage is not uncommon in Pennsylvania. I have also visited sites that experienced similar damage when the corn was in the pretassel stage. This can cause a phenomenon called greensnap, where the stalk is snapped off just below the ear. This causes localized areas in fields with up to 100% of the plants experiencing greensnap. In these cases the recovery potential of the damaged corn plants and also the surrounding undamaged corn plants are limited. In Midwest regions where high winds are common, corn hybrids are rated for their potential for greensnap.