By Osler Ortez, Ohio State University Extension
If you are familiar with “abnormal ears,” many ear symptoms can fall into that, but early to mid-June is the time when at least one of them can be mitigated: arrested ears. The term “arrested” is used because the development of these ears is interrupted or stopped prematurely due to external factors.
Symptom: arrested ears (ear development arrested or stopped prematurely).
Causal factor: applications of nonionic surfactant (NIS) formulations.
Development timing: during the ear size determination period, from V6–V12; and up to V16.
From field observations, the timing of the causal factor for arrested ears coincided with the timing of pesticide spray applications (e.g., post-emergence herbicide; and pre-tassel fungicide and insecticide applications), which often include nonionic surfactants (NIS) in the tank-mix (note: NIS may be already included in some pesticide products). Researchers started to look closely at nonionic surfactants as the potential cause. Years later, results confirmed nonionic surfactants (not the pesticide!) as the cause when applied anywhere between V6 and up to V16 stage in corn. The percentage of plants affected depended on hybrid, the plant stage when applications were made (e.g., applications at V15 resulting in more arrested ears than V11 applications), and management conditions that promoted faster plant growth (e.g., water and nutrient availability).
The partial solution to this phenomenon is to avoid applications of nonionic surfactants (NIS) during sensitive development stages in corn: V6 to V18 (6 to 18 collared leaves). For this and other reasons, understanding and keeping track of crop growth and development through the season is critical, especially when considering field applications. Development staging misunderstandings and applications at the wrong time can be conducive to these and many other issues. When staging, it is recommended to use the leaf collar method. At later vegetative stages, younger leaves have often senesced, staging using the split-stalk technique will help.
Regarding abnormal ears in general, several complexities and questions still need answers but with the knowledge available, abnormal ears can be seen as result of an “expression triangle” where susceptible hybrids, conducive environmental conditions, and unfavorable management practices can lead to abnormal ears. A classic example of this expression triangle is arrested ears. To learn more about this and other issues related to abnormal ears, a review of the literature is summarized here: https://doi.org/10.1002/agj2.20986.
During the growing season, the crop’s exposure to unfavorable conditions can negatively affect ear formation and produce abnormal ears. Abnormal ears decrease yield and can reduce grain quality.