Diagnose Corn Ear Problems

September 20, 2016 02:29 PM

Shape and condition can determine what went right or wrong

As days get shorter and the air begins to cool, it’s a sure sign harvest is nearing. As you check fields, take time to peel back a few husks and see how your in-season management played out this year. This end-of-season benchmark can be a critical tool to tweak hybrid selection and management practices in the future.

“Always look toward next year,” advises Jason Kelley, a wheat and feed grains Extension agronomist at the University of Arkansas. “We need to check our management results and hybrid performance.”

During the field check, know there’s little you can do to affect yield this season. Identify potential mistakes and develop a strategy to correct any issues. 


When checking ears, first look for the degree of kernel tip back, says Fred Below, professor at University of Illinois Crop Science department. “No tip back means you didn’t plant enough and ½" to 1" of tip back means you planted sufficient plants.”

While it sounds like a paradox—you want as many kernels per ear as you can, but you don’t want ears filled to the tip—you’re losing potential yield with too few plants. Look for straight ears with at least ½" of tip back, any less indicates your population was too low. In addition, if you’re seeing multiple ears per plant (aside from outer rows) you’re likely planting too low of a population.

“If you’re planting too light don’t go too far when correcting,” Kelley says. “Don’t spend more on seed for little returns.”

If you recognize you’re plant population was too low this year, try a boost of at least 2,000 plants per acre next year or talk with your seed sales rep or agronomist for specific hybrid tips. Flex ears might not need as substantial of a population boost while fixed ears could require more.

Tip back might not be an easy diagnosis, however. Population does play a role in kernel development, but it’s not the only factor.

“If it’s tipped back 2" or more and the ear tip is bent over it’s stress related,” Below says. 

A number of issues can cause stress to corn plants, but the two most likely culprits are weather or fertility issues. Because you can’t control weather, consider what fertility program you used.

Fertility issues, specifically nitrogen deficiencies are the easiest to identify, Below adds. The plant will have yellowing while it’s green, might die earlier, could have lower test weight and often doesn’t fill or aborts kernels at the tip.

Nitrogen application prior to planting might not meet corn needs throughout the entire season, especially with excess rain. For example, at tassel corn still has 40% of total nitrogen uptake to complete. If you apply nutrients in the spring that’s at least three months of rain, heat and other nitrogen-leeching mechanisms that could steal yield potential. If you notice tip back at the end of the season due to nitrogen, perform tissue tests at critical points throughout the season to determine if sidedressing could help.


Uneven emergence, even by just three or four days can have a lasting impact on the success of your crop. When plants get behind they can suffer during pollination, have poorer root systems and wimpy, underdeveloped ears. 

“From looking at a lot of high yielding plots the higher the ear is on the plant the better it yields,” Below says. He says the scientific reason for this is still unknown, but it’s a fact commonly recognized by high-yield growers.

Check the ear height along rows to determine how uniform your crop is and think back to planting, soil compaction, herbicide application and other management actions that influence growth. Identify the most likely culprit for non-uniformity and plan for next year.


When you’re peeling back husks you might find a deformed ear every so often. When “zipper ear” occurs, two or more entire rows of kernels are missing the length of the ear. “It’s not all that common and mostly associated with drought stress,” Kelley says. Areas with good rainfall or irrigation won’t see this phenomenon.


Another abnormality you might find in your field is arrested ear. The base of the ear might appear normal but kernel development up the ear is altered or ceases completely. “This is usually caused by surfactants added to herbicides or fungicides that are applied after the V8 growth stage but before VT (tasseling),” Below says.


Just like insects can cause damage to leaves and stalks, they can cause ear deformation. One example is “banana ear” caused by stink bugs feeding on developing kernels. The damage causes the ear to bend like a banana. Address this and other insect damage in your pest management strategy for next season.

While deformed ears are often few and far between, ear rots can impact yields. Examine ears to identify the culprit and devise a plan to address mycotoxins and other possible docks at the elevator.

Gibberella and Fusarium produce mycotoxins, but the more common Diplodia rot does not, according to Purdue University. Rots favor wet, humid conditions in the three weeks following silking. Other damage from insects can make ears more susceptible.

Gibberella shows pinkish red mold that moves from the tip to the base of the ear. Diplodia produces gray to black mold from the butt of the ear toward the tip. Fusarium shows gray discoloration scattered on individual or groups of kernels throughout the ear.





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