The sight of frost on an emerged corn field may leave you wondering if your crop has been injured. To answer this, we need to evaluate how low the temperature dropped, and the location of the growing point when the cold weather event occurred.
The growing point in corn remains below ground until growth stage V6 (6 leaf collars) and is protected from aboveground frost damage, unless the freeze was substantial.1 28° F is considered lethal to a corn plant whose growing point is aboveground, and can injure a growing point that is below ground if the temperature remained this low for more than a few hours. Signs of frost injury may be observed on the leaves of young plants, but if the growing point remains healthy, the plants should make a rapid and complete recovery. For more information on the growing point location at different growth stages, visit: https://www.agry.purdue.edu/ext/corn/news/timeless/GrowingPointsGallery.html
Symptoms of frost injury will start to show up about 1 to 2 days after a frost, and appear as leaves that look water-soaked, wilted, yellow, brown, and/or silver. Several days later, leaves may turn brown and die; however, if the growing point is not damaged there is a good chance for recovery and survival, particularly if there is new green tissue in the whorl leaves.2 If new leaves are not emerging, check the growing point for discoloration. A white or cream-colored growing point that is still firm is an indication that the plant is recovering, while growing points that are darkened and soft are likely to die.
If weather conditions are beneficial for recovery, a new leaf should develop three to four days after the frost. Occasionally, decaying leaf tissue may inhibit the growth of new leaves from the whorl, giving the corn seedling a twisted appearance.2 In most situations the new growth will grow through the decaying tissue. Continue to scout corn to detect any problems that may require corrective action.
The best thing you can do is to wait 3 to 5 days before making a field-by-field assessment of frost damage.3 At that point, surviving corn plants should have new leaf tissue beginning to expand from the whorls, while dead plants will not.2 Dry, warm conditions will favor recovery, while multiple frost events or cool, damp weather can compromise recovery and plant health. Corn survival is dependent on a healthy growing point and new leaf growth. The best management practice is to exercise patience and to scout your fields. Evaluate your existing stand for potential survival and uniformity before deciding to replant. Compare the yield potential of the existing stand with the yield potential of a replanted stand. For more information on Corn Replanting Decisions, visit:https://www.channel.com/agronomics/Pages/Corn-Replanting-Decisions.aspx
1 Elmore, R.W. 2015. Impact of early season frost (before V4). Iowa State University. https://crops.extension.iastate.edu/corn/production/management/planting/frost.html
2 Nielsen, R. 2001. Frost and low temperature injury to corn and soybean. Corny News Network. Purdue University. https://www.agry.purdue.edu/ext/corn/news/articles.01/frost_corn_soy-0418.html;
3 Nielson, R. 2017. Assessing frost/cold temperature injury to young corn. Purdue University. Corny News Network;
4 Nielsen, R. 2008. Growing point location in corn at different growth stages. Purdue University. Corny News Network. Purdue University. https://www.agry.purdue.edu/ext/corn/news/timeless/growingpointsgallery.html
Web sources verified 02/26/18. 15051415293