Agronomy Talk

Agronomy Talk: EAR DEFORMITIES

Published on Monday, November 04, 2019

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STRESS AND EAR FORMATION

Ear and kernel development is a lengthy process for a corn plant. It begins at the V5 growth stage as the plant determines kernel rows around and then continues to V12 where the potential maximum length of the ear is determined. Next comes the pollination stages where the maximum number of kernels is established and then finally, R5 when the maximum kernel size is established.

Any stresses, natural or manmade, during this process, can lead to abnormal ear set. Many of the abnormal ears and their causes are detailed below. Accurate diagnosis of these abnormalities can help prevent future problems in the field.

INCOMPLETE KERNEL SET:

  • Symptom: Few, if any, pollinated kernels on the ear.
  • Cause: Unsuccessful pollination, which could be due to many factors including heat/drought stress, silk clipping, herbicide injury, or simply uneven crop development, ultimately affecting the timing of both viable pollen and silks being present at the same time.

EAR TIP DIEBACK:

  • Symptom: Unfilled ear tips with little kernel development that appear dried and shrunken.
  • Cause: Severe stress during the early grain fill period, typically during the blister stage. This is often associated with nitrogen deficiency, but could also be caused by severe heat/drought stress or limited grain fill due to extended cloudy weather.

ZIPPER EAR (BANANA EAR):

  • Symptom: Zipper ear often occurs when kernel abortion occurs across entire rows of an otherwise normally developed ear. As unaffected kernels continue to develop, the ear will bend and take on a banana-like, curved shape.
  • Cause: Severe stress during the early grain fill period, silk balling, and other issues related to silking.

PINCHED EAR (BEER BOTTLE EAR):

  • Symptom: Normal length of the ear and the butt of the ear displays typical kernel rows around. However, kernel rows around decreases abruptly further up the ear, “pinching” to form the tapered shape of a bottle.
  • Cause: Severe stress between V7 to V10 can cause this phenomenon; however, it is often associated with late post-emergence ALS herbicide applications.

BLUNT EAR (BEER CAN EAR):

  • Symptom: The ear will exhibit near-normal girth and kernel rows around; however, the length of the ear will be drastically shorter than normal, leaving the tip barren in most cases.
  • Cause: Severe stress during the later stages of ear development (V8 to V12), including multiple herbicide and fungicide/insecticide applications (due to included surfactants), can cause this deformity.

TASSEL EAR:

  • Symptom: Ear development where a tassel would normally be located at the terminal end of the plant. Most commonly, this occurs on tillers/suckers of an otherwise normal plant.
  • Cause: This is caused by a hormonal imbalance when either the growing point of the plant is compromised (frost, mechanical injury, etc.) or when there is excessive tillering along field edges or in areas that are underpopulated.

BOUQUET EAR:

  • Symptom: When multiple ears originate from a single node. These ears will typically have reduced kernel numbers; however, kernel row length can be normal. This occurs sporadically within the field.
  • Cause: The cause of this ear deformity is unknown, however, it is commonly associated with brief, cold stress during the early ear formation stages.

INCOMPLETE BASAL FILL:

  • Symptom: Very few kernels, if any, are present at the basal portion of the ear.
  • Cause: Numerous stresses including drought at the onset of pollination, lack of available pollen during ear pollination, or the clipping of silks from insects during this time.

 

CLICK HERE FOR A DOWNLOADABLE VERSION OF THIS AGRONOMY TALK UPDATE

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Travis Burnett
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Travis Burnett

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