Events that take place during the V7 to V10 growth stages have an impact on the number of kernel rows the ear develops. When stresses are present, the number of kernel rows will be reduced. For example, an ear of corn that pinches in and narrows as it reaches the top could have been caused by the stress of a late herbicide application. In this scenario, the number of kernel rows per ear decreases from the bottom to the top of the ear (i.e. it has 16 at the bottom and by the top only 8 kernel rows/ear). This situation is called "Ear Pinching" or "Beer Bottle" Ears.
If you notice the ears of corn are reduced in size and kernel numbers per row, then you might have experienced Blunt Ear Syndrome (Also known as "Beer Can" Ears or Ear Stunting). The true cause of Blunt Ear Syndrome is unknown. It is sometimes associated with multiple ears at a node; however, it is usually rare and sporadic within a field. During the V8 to V12 growth stages, the length of the ear is impacted. Stress during this time is what can cause those blunt ears of corn. Stress at this time could be caused by drastic temperature changes and sometimes pretassel application of some foliar chemicals.
Small misshaped ears with poor kernel set around the ear tip are associated with Nubbin Ears. This is often caused by severe drought from mid vegetative growth through early to mid-grain fill. Occasionally it has been known to be associated with nitrogen deficiency and high plant populations. One of the best ways to avoid Nubbin Ears is by maintaining appropriate soil fertility, adjusting planting depth with varying soil conditions, and selecting hybrids and seeding rates consistent for soil yield potential and planting date.
Zipper Ears (or Banana Ears) are associated with missing entire or parts of kernel rows on the underside of the ear due to kernel abortion. Occasionally the ear will even bend and look like a banana. The true cause of Zipper Ear is unknown, but it has been linked to severe drought stress or defoliation injury following pollination.
Hopefully, no farmer is finding any of these abnormal ears in their fields.
However, if they are, those ears will provide the farmer with a glimpse into what did or did not happen this growing season if he is able to identify the type of abnormality present.
As always, if you have any questions or would like information on any agriculture, horticulture, or natural resource topic, then please contact your local Purdue Extension Office at 448-9041 in Clay Co. or 829-5020 in Owen Co. or reach me directly at email@example.com. Purdue University is an equal opportunity/equal access/affirmative action institution.
Upcoming opportunities available to you through Purdue Extension include:
October 17--Final Master Naturalist Class Session, 6:00-9:00PM, Clay Co. Extension Office
October 17 -- Clay Co. Extension Office is Closed -- Staff Training
October 17 -- Owen Co. 4-H Awards Night
Oct. 24 -- 26 -- Owen Co. National Meat Judging Team Trip to Kansas State University
October 20--Calico Extension Homemaker's Club Meeting
October 20 -- Clay Co. 4-H Adult Leader Meeting at 7:00 PM