Watch Corn Rev Up at V6

Warm temperatures tend to push corn off the starting line faster than a turbocharged race car. Going from zero to 60 isn't exactly a bad thing in the crop, but it increases the need to mitigate risk with timely management during critical growth stages.

The car metaphor seems to fit because V6 is a critical period when the number of kernel rows per ear is determined, as outlined in a recent LG Seeds news release.

Shane Irlbeck, an LG Seeds agronomist based in southern Minnesota, said the four key windows when corn yield is most influenced by management include: VE, V6, V10-V12 and R5-R6.

Putting boots in the field is still the best way to observe what challenges a particular field during each of those stages. Knowing what specifically to be on the alert by growth stage also helps refine scouting tactics. Planting has been delayed in many regions this spring and growth stages could range from field-to-field.

For example, in some cases, such as black cutworm, corn can outgrow the threat, and treatment is generally not warranted after V5. Read more here: https://www.dtnpf.com/…

The Land Grant Universities define corn growth stages and provide solid scouting information through the Crop Protection Network. Find it here:

https://cropprotectionnetwork.org/…

Seed companies have also developed scouting charts that correspond to growth stages. The LG Seed chart is easy to follow and gives management tips by growth stage. Find it here: https://lgseeds.com/….

V6 WINDOW TO WATCH

By V6, plant stands are established, rapid stem elongation begins and the number of kernel rows per ear is being determined. During this period, you want the plant focused on building yield, not battling stress, Irlbeck noted.

According to the company's scouting guide V6 is the time to specifically watch for:

--Disease: Goss's Wilt, Stewart's leaf blight, common rust, gray leaf spot, northern leaf blight, eyespot

--Insects: Corn rootworm, European corn borer, common stalk borer, fall armyworm, southwestern corn borer, corn leaf aphids

--Other vulnerabilities: Nutrient deficiencies, hail, freeze, flooding

"Drought or crop stress at this time can impact the yield potential we're setting up for the year," he said. "The crop's ability to overcome V6 stressors depends in part on whether it flexes in ear length or girth or by kernel depth, but regular scouting and an appropriately timed fungicide application can help in either scenario."

The V6 stage is when nitrogen uptake begins, and he urged growers to watch for nutrient deficiencies and be prepared to correct them.

"If you have it in your program to do some side-dress nitrogen, V6 to V8 is an optimal time because it's not long until we're pushing tassels," he noted, pointing to University of Nebraska research that shows corn uses up to 70% of its nitrogen before R1 (https://digitalcommons.unl.edu/…).

"The rapid growth period from V7 to tassel is when most of the nitrogen in that plant is taken up and used," Irlbeck explained. "Make sure you have enough fertilizer up front or split-applied."

"If you see nutrient deficiencies, a foliar or a soil-applied rescue application can help, but keep in mind that some damage has already been done," Irlbeck said. "It's better to be out there, know you have an issue at the time and take action than wondering why it yielded poorly."

You may also start to see suckers or tillers appear on the plant at V6, but that can be good news. "Tillered corn is happy corn," Irlbeck said. "That typically means it has enough nutrients and moisture that it thinks it can throw another stalk out there."

PUT LATE CORN TO THE TEST

Have late corn? Taking time to score emergence on later planted stands can also help fine-tune management. AgriGold agronomist Brett Leahr talks about that here: https://agrigold.com/….

Read more about how you can perform similar flag emergence tests and what the test can tell you in DTN's coverage: https://www.dtnpf.com/….

Find the complete news release on monitoring V6 growth stages from LG Seeds here: https://lgseeds.com/….

Pamela Smith can be reached at pamela.smith@dtn.com

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