Cold temperatures and injury to newly planted corn
Newly Emerged Corn
Damage from exposure of above-ground plant tissue to frost can range from minor leaf injury to complete death of all exposed leaf tissue. That's the bad news. The good news is that the all-important growing point region of a young corn plant remains below the soil surface, safe from exposure to frost, until the V4 to V6 stages of development. That means that the above-ground plant tissue you see in fields younger than about V4 is composed primarily of leaves and rolled up leaf tissue in the whorl, but does not include stalk tissue or the growing point. As long as temperatures are not lethally cold, "simple" frost injury usually does not literally kill such young corn plants. Damaged plants will begin to show recovery from the whorl within 5 to 7 days, depending on temperatures following the frost event.
Disclaimer: Repeated frost events that re-inflict damage to recovering corn plants can cause permanent stunting or death.
When folks worry about the effects of cold weather on corn, they often fail to distinguish between simple frost events and lethal cold temperatures. Frost can occur at temperatures easily up to the high 30's F, but lethal cold temperatures for corn are generally thought to be 28F (-2C) or colder. With little to none of the 2014 corn crop emerged to date plus the near absence of such low temperatures in the past week or so, I doubt that any above-ground injury to "early" planted corn has yet occurred.
Only time will tell whether corn planted during the past couple of weeks has suffered from the cool soils during germination. Obviously, those "early" planted fields should be scouted over the next few weeks for emergence problems. Come October, we will know for certain whether this year's early planting risk takers will have "won the game" or not.
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