frost and freeze damage to corn
Near to below freezing temperatures can damage emerged corn. The amount of damage depends on air temperature, soil moisture, stage of growth, residue, tillage, and length of cold. This issue of Wyffels Between the Rows® will provide guidance on how and when to evaluate potential frost damage of emerged corn.
Patience is Key
The growing point of a corn plant remains about 1/2 inch below ground until about the 5-collar stage, which keeps the plant reasonably protected from the effects of above ground frost. Frost damage to corn is usually minor and limited to above ground plant tissue. Corn can easily recover from this type of injury early in its development and suffer minimal yield loss.
When air temperatures drop to lethal levels (28° F or less) for more than a few hours, the growing point of a young corn plant can be injured or killed even if it is still below the soil surface. The degree of lethal damage that occurs (even at 28° F or less) depends on your soil type and the amount of moisture in your soil. Corn plants in sandy soil or in very dry soil are more prone to freeze damage. Corn planted in low-lying areas may actually drop below the freezing mark quicker than other spots in the field.
The key requirement for assessing frost damage is to be patient and to allow the plants to recover. While corn leaves may blacken and wither within a day after frost occurs, the true extent of plant damage may not be evident. After three to five days, surviving corn plants should be showing new leaf tissue expanding from damaged whorls. If a significant portion of the population is obviously dead after this same period of time, then replanting may be justified.
Another way to assess whether a plant will survive is to dig up the plant, split it in half, and inspect the growing point (crown). The growing point of VE to V1 corn can be identified by finding the swollen area between the seed and above ground stem and leaves. Nodal roots are typically evident at the growing point of V2 and older plants. A brown discoloration of the growing point would indicate the plant will not survive. A white or light-yellow color indicates a live plant with a chance to continue development.
Another point to keep in mind is frost damaged corn is developmentally older than what a recovered plant shows. For example, if a V2 plant loses both of its leaves to frost damage and grows three new leaves, the plant is actually a V5 plant even though it only has three visible leaves. This is a common misunderstanding that can have negative effects, especially if you apply an herbicide when the corn plant is actually at V6 or V7, but you thought it was only V3-V5.
