Have you seen these abnormal ears?

Of Osler Ortez AND Dan Quinn

Abnormal ears of corn are found across the country from Kansas and Nebraska in the Western Corn Belt to Indiana and Ohio in the Eastern Corn Belt, and everywhere in between. They can develop in any region if corn is grown there.

Abnormal ear problems have been seen as a sporadic concern. However, 2016 was the year that abnormal ears were no longer necessarily just sporadic. Widespread abnormal ear development has been reported in several US states, including Texas, Colorado, Kansas, Nebraska, Iowa, and Illinois.

Since then, agronomists have paid more attention to abnormal ear development. Here are some comments from the authors:

Ortez: As the saying goes, every adversity, every failure, every heartache brings with it the seed of an equal or greater benefit. This is attributed to Napoleon Hill. Widespread concern about abnormal ears seen in agricultural fields across the United States was the seed that sparked dedicated efforts and research to better understand the phenomenon. The efforts were initially led by University of Nebraska-Lincoln researchers, including myself, Roger Elmore, and Justin McMechan, along with a larger team that included farmers, state corn specialists, extension educators, industry experts seed and plant breeders.

From 2016 to 2021, intensive research took place on the farm and in small plots. After nearly six years, not all questions were answered, but some were. You’ll find insight into what that team discovered as you view each of these anomalies in the accompanying presentation.

Quinn: Bob Nielsen has observed his fair share of abnormal ear types during his career as a corn specialist at Purdue Extension. He was frequently contacted by breeders who noticed unusual ears and sought an explanation. Nielsen visited many of those fields, taking pictures and actively pursuing theories. He often looked back at the start of the season, accounting for weather conditions where the corn plants would have made key decisions about ear length, kernel count and more.

Even when I started my career, I still found abnormal ear types in the cornfields of Indiana. Our goal is to continue to explore causes and fixes for glitches. Hopefully, you won’t find them all in any season, but you might find one or more in any given year. Let us know, so we can further investigate why they occur.

Why anomalies occur

There are distinct differences between normal and abnormal ears, one of which is the ability to produce yield. The abnormal ears show distinctive breaks in the development of husk cobs, grains, or leaves. Abnormal ears include tassel ears, stunted ears, ears with coblike curvatures, ears without viable or exposed bristles, ears with unusual patterns of pollination failure or seed abortion, plants with more than one ear on the same ear stalk, with grains sautéed along the cob and ears not adequately covered by hull leaves.

In 2016, a survey of 15 fields of Nebraska growers showed that affected fields had an average of 26 percent abnormal ears. Abnormal ears reduced grain yields by 35% to 91%. Yield reductions depended on symptoms, frequency and severity of abnormal ears. In these field evaluations, the placement of abnormal ears suggested that primary ear abortion was a related factor because the abnormal ears appeared to be located on lower lymph nodes.

Current knowledge suggests that ear abnormalities result from cumulative interactions between genetics, environment, and management practices. For example, plant stresses imposed by susceptible hybrids, unfavorable growing conditions, and specific favorable management practices interact and amplify the severity and frequency of these problems.

Exposing crops to unfavorable conditions during the growing season can have a negative impact on ear formation and yield, especially at critical moments when plants make decisions. The timeline for corn development shows when these decisions occur.

Understanding the conditions that potentially affect ear formation, yield and abnormal ears at these key times is critical. A big key is when there is potential stress related to ear formation.

A closer look at ear abnormalities

See if you recognize these ear anomalies. The descriptions can help determine what led to this condition in your field. To see the photos, see the slideshow.

Symptom 1: Tassel ears
Description: Ears on top of the crumpled plants instead of tassels
Causative factors: Lower populations, fine or border rows, growth point damage, genetics
Development times: Initiation and differentiation of grower apical meristem in floral structure

Symptom 2: Bandaged ears
Description: Kernel lines increased and not organized
Causative factors: Specific mutants in genetics, low temperatures
Development times: Ear initiation and development, V4 to V7

Symptom 3: Blocked ears
Description: Ear development has stopped or stopped prematurely
Causative factor: Applications of nonionic surfactant (NIS) formulations.
Development times: Determination of ear size, from V6 to V12 and up to V16

Symptom 4: Pinched ears
Description: Abrupt switch to fewer kernel files in the ear
Causative factors: Cell division inhibitors, for example, sulfonylurea herbicides
Development times: Determination of ear size, from V6 to V12

Symptom 5: Blunt ears
Description: Noticeably shorter, stunted ears, also called beer can ears
Causative factors: Plant stressors such as chemicals or environment, genetics, management
Development times: Determination of ear size, from V6 to V12

Symptom 6: Balled ears of silk
Description: The silks fail to stretch properly towards the tip of the ear
Causative factors: Cold, drought, genetics
Development times: Silk elongation, from V12 to R1

Symptom 7: Incomplete kernel set
Description: Sparse or scattered kernel set
Causative factors: Silk damage, drought, high temperatures, pollination problems, phosphorus deficiency, herbicide damage, cloudy days
Development times: Pollination, VT or R1; and the early reproductive stages, R1 to R3

Symptom 8: Banana ears
Description: Curvature of the cob towards the damaged side of the ear
Causative factors: Severe weather conditions, chemical applications, heat or drought, bed bug injuries
Development times: Pollination, VT or R1; and the early reproductive stages, R1 to R3

Symptom 9: Zippered ears
Description: Ears with missing kernel files
Causative factors: Higher seeding rates, drought stress, genetics, defoliation, poor pollination
Development times: Pollination, VT or R1; and the early reproductive stages, R1 to R3

Symptom 10: Ears tilted back
Description: Nuts missing on ear tip
Causative factors: Pollen and silk availability, stone abortion, cloudy days, heat, drought, genetics, higher seeding rates
Development times: Pollination, VT or R1; and the early reproductive stages, R1 to R3

Symptom 11: Multiple ears per node
Description: Multiple ears at single stem nodes or on the same ear stem
Causative factors: Environmental stresses such as cold, low seed rates, genetics, primary ear damage
Development times: After ear initiation at V4 to V6 and before pollination at VT or R1

Symptom 12: Rocker ears
Description: Missing kernels and diameter decreases in the cob
Causative factors: Heat stress, limited solar radiation, ethylene, hormones, chemical applications, genetics, primary ear damage
Development times: Determination of ear size, from V6 to V12 and up to R1

Symptom 13: Short-skinned ears
Description: Shortened husk leaves with ears protruding beyond the husks
Causative factors: Short-term stress such as heat or drought followed by colder temperatures and precipitation, high-velocity winds or storms, genetics
Development times: Close to napping and pollination, V18 to R1

Ortez is an agronomist and corn specialist at Ohio State University. Lui presented a comprehensive report on abnormal ears at the Indiana Certified Crop Advisers Conference in December. Quinn is Purdue Extension’s corn specialist. Some of the photos provided for the presentation were from Bob Nielsen, retired Purdue Extension corn specialist. Nielsen studied abnormal ear development during his four-decade career at Purdue. Contact Ortez al [email protected] and Quinn A [email protected].


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