Other Corn Ear Abnormalities – when and why do they develop?

Despite many corn acres having reached tasseling, other corn acres are still in rapidly growing stages, mid to late vegetative. Any adverse conditions can still affect the crop through or prior to harvest. Arrested ears occurrence was discussed two weeks ago. Other ear abnormalities of concern up to this point in the season can include tassel ears, fasciated ears, pinched ears, blunt ears, silk-balled ears, incomplete kernel set, banana ears, zipper ears, and tipped back ears.

Based on existing knowledge, table 1 and the following figures present a summary of these abnormalities, including the possible causal factors and their expected timing of development. Plant stages used here are based on the leaf collar method.

Table 1. Summary of various abnormal ear symptoms, their causal factors, and development timing. Adapted from Ortez et al., 2022a.

Symptom

Possible causal factors

Development timing

Figure

1. Tassel ears: ears at the top of tiller plants in place of tassels

Lower populations, end or border rows, growing point damage, genetics

Initiation and differentiation of tiller’s apical meristem into floral structure

1

2. Fasciated ears: increased and non-organized kernel rows

Specific mutants (i.e., genetics), cold temperatures

Ear initiation and development, V4V7

2

3. Pinched ears: abrupt change to fewer kernel rows in the ear

Cell division inhibitors, for example, sulfonylurea herbicides

Ear size determination period, V6V12

3

4. Blunt ears: noticeably shorter and stunted ears

Plant stressors (e.g., chemicals or environment), genetics, management

Ear size determination period, V6V12

4

5. Silk-balled ears: silks fail to elongate toward the ear tip properly

Cold temperatures, drought, genetics

Silk elongation, V12R1

5

6. Incomplete kernel set: poor or scattered kernel set in the ear

Silks damage, drought, high temperatures, pollination issues, phosphorus shortages, herbicide injury, cloudy days

Pollination, VT or R1; and early reproductive stages, R1R3

6

7. Banana ears: the curvature of the cob toward a damaged side of the ear

Severe weather, chemical applications, heat or drought, stink bug injury

Pollination, VT or R1; and early reproductive stages, R1R3

7

8. Zipper ears: ears with missing kernel rows

Higher seeding rates, drought stress, genetics, defoliation, deficient pollination

Pollination, VT or R1; and early reproductive stages, R1R3

8

9. Tipped-back ears: missing kernels at the tip of the ear

Pollen and silk availability, kernel abortion, cloudy days, heat, drought, genetics, higher seeding rates

Pollination, VT or R1; and early reproductive stages, R1R3

9

 

1. Tassel ears

Figure 1. (a) Complete replacement of tassel and (b–c) partial replacement of tassel on tillers in an end row. Images: (a) Osler Ortez, (b–c) Robert Nielsen.


2. Fasciated ears

Figure 2. Fasciated popcorn ear with seven ear branches. (a) Side and (b) top views. Images: Osler Ortez.


3. Pinched ears

Figure 3. Corn ears at different developmental stages. (a) Mature pinched ear due to sulfonylurea herbicide applied between V7 and V10 stages, (b) developing ear at the V9 stage, and (c) developing ear at V12 stage. Images adapted from Strachan (2010). Images: (a–b) Antonio Perdomo, (c) Stephen Strachan.

4. Blunt ears

Figure 4.
Blunt ears, beer-can ears, or stunted ears. (a) The similarity in kernel row number of a blunt ear compared with a normal ear, but with arrested ovule and kernel development. (b) Different degrees of arrested development in blunt ears. Images: (a) Robert Nielsen, (b) Peter Thomison.


5. Silk-balled ears

Figure 5.
(a–b) Silk-balled ears or scrambled silks, silks growing in different directions trapped within the husk and (c) ears with various severity levels of damage. Images: Robert Nielsen.


6. Incomplete kernel set

Figure 6.
(a) Ears displaying incomplete kernel set; and (b–c) silk-clipped ears, damage caused by insect clipping before or during pollination. Images: (a) Peter Thomison, (b) Robert Nielsen, (c) Osler Ortez.

7. Banana ears

Figure 7.
Banana ears exhibit curvature along the cob shape with different degrees of damage (A, B, C). Husk leaves were removed (if needed) for better symptom visibility. Images: Osler Ortez.


8. Zipper ears

Figure 8.
(a) Zipper ears increase at higher seeding rates; from left to right (three ears per treatment): 62,000, 86,000, and 111,000 seeds per hectare. (b) Ear with several kernel rows missing due to pollination or abortion issues, husk leaves were removed for better symptom visibility. Images: (a) Peter Thomison, (b) Osler Ortez.


9. Tipped-back ears

Figure 9.
Tipped-back ears with unfilled kernels towards the tip. (a) Ear with about 50% tipped back, (b) about 25% tipped-back, (c) about10% tipped-back, and (d) about 5% tipped back. Husk leaves were removed for tip-back visibility. Images: (a, b, and d) Osler Ortez, (c) Justin McMechan.

To learn more about these and other abnormal ears, a literature review is summarized here: https://doi.org/10.1002/agj2.20986. For more resources, previous work in Ohio has a comprehensive summary available, Troubleshooting Abnormal Corn Ears: https://u.osu.edu/mastercorn/.

When it comes to abnormal ears, questions still need answers. However, with the knowledge available, abnormal ears can be seen as the result of an “expression triangle” where susceptible hybrids, conducive environmental conditions, and unfavorable management practices can result in abnormal ears. The crop’s exposure to unfavorable conditions can negatively affect ear formation and produce abnormal ears. Abnormal ears reduce yield and can reduce grain quality too.

References

Ortez, O. A., McMechan, A. J., Hoegemeyer, T., Ciampitti, I. A., Nielsen, R., Thomison, P. R., & Elmore, R. W. 2022a. Abnormal ear development in corn: A review. Agronomy Journal, 114, 1168– 1183. https://doi.org/10.1002/agj2.20986

Ortez, O. A., McMechan, A. J., Hoegemeyer, T., Ciampitti, I. A., Nielsen, R. L., Thomison, P., Abendroth, L. J., & Elmore, R. W. 2022b. Conditions potentially affecting corn ear formation, yield, and abnormal ears: A review. Crop, Forage & Turfgrass Management, 8, e20173. https://doi.org/10.1002/cft2.20173

Ortez, O. A., McMechan, A. J., Hoegemeyer, T., Rees, J., Jackson-Ziems, T., & Elmore, R. W. 2022c. Abnormal ear development in corn: A field survey. Agrosystems, Geosciences & Environment, 5:e20242. https://doi.org/10.1002/agg2.20242

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