by Osler Ortez and Dan Quinn

Abnormal corn ears are found all over 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 issues have been viewed as a sporadic concern. However, 2016 was the year when abnormal ears were not necessarily only sporadic anymore. Widespread abnormal development of ears was reported in several U.S. states, including Texas, Colorado, Kansas, Nebraska, Iowa and Illinois.

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

Ortez: As the saying goes, “Every adversity, every failure, every heartache carries with it the seed of an equal or greater benefit.” That is credited to Napoleon Hill. Widespread concern about abnormal ears observed in farm fields across the U.S. was the seed that triggered dedicated efforts and research to better understand the phenomenon. Efforts were initially led by University of Nebraska-Lincoln researchers, including myself, Roger Elmore and Justin McMechan, alongside a broader team that spanned from farmers, state corn specialists, Extension educators, seed industry experts and plant breeders.

Intense on-farm and small-plot research took place from 2016 to 2021. After nearly six years, not all questions had answers, but some did. You will find information on what that team discovered as you view each of these abnormalities in the accompanying slideshow.

Quinn: Bob Nielsen observed his fair share of abnormal ear types during his career as a Purdue Extension corn specialist. He was often contacted by farmers who noticed unusual ears and sought an explanation. Nielsen visited many of those fields, taking pictures and actively pursuing theories. Often, he looked back to the beginning of the season, taking into account weather conditions when corn plants would have made key decisions about ear length, kernel count and more.

Even as I start my career, we’re still finding abnormal ear types throughout cornfields in Indiana. Our goal is to continue to explore causes and remedies for abnormalities. Hopefully, you won’t find all of them in any one season, but you may find one or more in any given year. Let us know, so we can further investigate why they occur.

Why abnormalities occur

Distinct differences exist between normal and abnormal ears, one being the capacity to produce yield. Abnormal ears show distinctive disruptions in development of cob, kernels or husk leaves. Abnormal ears include tassel ears, arrested ears, ears with cob curvatures, ears without viable or exposed silks, ears with unusual patterns of failed pollination or kernel abortion, plants with more than one ear on the same ear shank, ears with kernel skips along the cob, and ears inadequately covered by husk leaves.

In 2016, a survey in 15 Nebraska grower fields showed affected fields averaged 26% abnormal ears. Abnormal ears reduced grain yield by 35% to 91%. Yield reductions were dependent on symptoms, frequency and severity of the abnormal ears. On these field assessments, placement of abnormal ears suggested abortion of the primary ear was a correlated factor because the abnormal ears seemed to be located on lower nodes.

Current knowledge suggests ear abnormalities result from cumulative interactions among genetics, environment and management practices. For example, plant stresses imposed by susceptible hybrids, unfavorable growing conditions and specific conducive management practices interact and magnify severity and frequency of these issues.

The crop’s exposure to unfavorable conditions during the growing season can negatively impact ear formation and yield, especially at critical times when plants make decisions. The timeline for corn development shows when these decisions occur.

Understanding conditions potentially affecting corn ear formation, yield and abnormal ears at these key times is critical. One big key is when potential stress occurs relative to an ear’s formation.

Closer look at ear abnormalities

See if you recognize these corn ear abnormalities. Descriptions may help determine what led to this condition in your field. To see photos, check out the slideshow.

Symptom 1: Tassel ears
Description: Ears at top of tiller plants in place of tassels
Causal factors: Lower populations, end or border rows, growing point damage, genetics
Development timing: Initiation and differentiation of tiller’s apical meristem into floral structure

Symptom 2: Fasciated ears
Description: Increased and non-organized kernel rows
Causal factors: Specific mutants in genetics, cold temperatures
Development timing: Ear initiation and development, V4 to V7

Symptom 3: Arrested ears
Description: Ear development arrested or stopped prematurely
Causal factor: Applications of nonionic surfactant (NIS) formulations
Development timing: Ear size determination, V6 through V12 and up to V16

Symptom 4: Pinched ears
Description: Abrupt change to fewer kernel rows in the ear
Causal factors: Cell division inhibitors — for example, sulfonylurea herbicides
Development timing: Ear size determination, V6 through V12

Symptom 5: Blunt ears
Description: Noticeably shorter and stunted ears, also called “beer can ears”
Causal factors: Plant stressors like chemicals or environment, genetics, management
Development timing: Ear size determination, V6 through V12

Symptom 6: Silk-balled ears
Description: Silks fail to elongate toward ear tip properly
Causal factors: Cold temperatures, drought, genetics
Development timing: Silk elongation, V12 through R1            

Symptom 7: Incomplete kernel set
Description: Poor or scattered kernel set
Causal factors: Silk damage, drought, high temperatures, pollination issues, phosphorus shortages, herbicide injury, cloudy days
Development timing: Pollination, VT or R1; and early reproductive stages, R1 to R3

Symptom 8: Banana ears
Description: Curvature of the cob toward damaged side of the ear
Causal factors: Severe weather, chemical applications, heat or drought, stinkbug injury
Development timing: Pollination, VT or R1; and early reproductive stages, R1 to R3

Symptom 9: Zipper ears
Description: Ears with missing kernel rows
Causal factors: Higher seeding rates, drought stress, genetics, defoliation, deficient pollination
Development timing: Pollination, VT or R1; and early reproductive stages, R1 to R3

Symptom 10: Tipped-back ears
Description: Missing kernels at tip of ear
Causal factors: Pollen and silk availability, kernel abortion, cloudy days, heat, drought, genetics, higher seeding rates
Development timing: Pollination, VT or R1; and early reproductive stages, R1 to R3

Symptom 11: Multiple ears per node
Description: Multiple ears at individual stalk nodes or on same ear shank
Causal factors: Environmental stress like cold, low seeding rates, genetics, damage to primary ear
Development timing: After ear initiation at V4 to V6 and before pollination at VT or R1

Symptom 12: Barbell ears
Description: Missing kernels and diameter decrease in cob
Causal factors: Temperature stress, limited solar radiation, ethylene, hormones, chemical applications, genetics, damage to primary ear
Development timing: Ear size determination, V6 through V12 and up to R1

Symptom 13: Short-husk ears
Description: Shortened husk leaves with ears protruding beyond husks
Causal factors: Short-term stress like heat or drought followed by cooler temperatures and precipitation, high-speed winds or storms, genetics
Development timing: Close to tasseling and pollination, V18 to R1

Ortez is an agronomist and corn specialist at Ohio State University. He presented a full report on abnormal ears at the Indiana Certified Crop Advisers Conference in December. Quinn is the Purdue Extension corn specialist. Some photos for the presentation came from Bob Nielsen, retired Purdue Extension corn specialist. Nielsen studied abnormal ear development throughout his four-decade career at Purdue. Read the full scientific paper online. Contact Ortez at [email protected] and Quinn at [email protected].