Agronomy Talk

Agronomy Talk: Early-Season Frost Damage

Published on Friday, March 01, 2019

CLICK HERE FOR A DOWNLOADABLE VERSION OF THIS AGRONOMY TALK UPDATE

Early-season frost damage is a stressful physiological event that can slow plant development. The net impact of early-season frost on a corn or soybean plant will depend on the health of the plant before the frost, the extent, and duration of the freezing temperature, and the growing environment following the frost event.

In general, corn seedlings are at a lower risk of death from freezing temperatures than are soybeans because the growing point of corn remains below ground later in the spring until the V5-6 growth stage.

Where to Look:

  • Low lying areas: Even a 1 to 2’ depression is more vulnerable to frost
  • High residue areas: Residue slows the springtime soil warming processes
  • Dry, loose soils: They tend to lose heat more rapidly than moist or compacted soils

Freeze Damage on Plant Tissue:

  • Water within the leaf freezes, rupturing cells

Corn

Frost damage on emerged corn plants has been observed from April until mid-June. Corn plants will not be killed by frost unless temperatures drop low enough to drive the cold into the soil and kill the growing point that is positioned 0.75 in. below the soil surface. Corn that has not emerged is typically well insulated from frost damage. 

Most Vulnerable:

  • Recently emerged or early vegetative growth with tender leaves
  • Anytime air temperatures dip below 32°F for extended periods

Symptoms:

  • Show up one to two days after the freeze event
  • Water soaked leaves
  • Leaves turn limp and brown
  • Three to four days later, new green leaves will emerge from the whorl

Check for Long-Term Damage:

If, after three or four days, new leaves are not visible or emerging, check the growing point for discoloration. Carefully dig the young plant from the soil and split the plant lengthwise to observe the growing point. Healthy tissue will be white, cream or light-yellow color – any other color indicates that the growing point is damaged. A common complication of a strong frost or light freeze on V2 to V3 growth stage corn is that the leaf-tips get “tied-up” and further restrict new leaf emergence. Under subsequent cloudy, cool and moist conditions, visual recovery can take 7 to10 days.


Corn plants with damaged leaf tissue will often get “tied up” when they grow new, healthy tissue.
These plants will recover from frost. Photo: Luke Schulte

 


In this picture, the growing point is water soaked and dark- this plant will not recover from this damage.
Photo: Luke Schulte
 

Soybeans

Although subject to frost as well, soybeans often escape similar injury due to plant development and to typical planting dates past the average last frost date.

Upon emergence, the growing point of a soybean plant is above the soil surface and less insulated against frost. Soybean cotyledons are thick compared to leaves. Therefore, cotyledon stage soybeans are more tolerant to freezing temperatures than older soybean or young corn leaves. When the frost only affects the top of the soybean plant, those plants with one or more intact cotyledons recover from surviving axillary buds.

Most Vulnerable:

  • If the air temperature stays at or below 28 to 30°F for several hours
  • Hooking stage soybeans will be killed if the hypocotyl tissue below the cotyledons is killed

Symptoms:

  • Water-soaked lesions on the cotyledons, leaves or hypocotyl

Check for Long-Term Damage:

  • Check for firm, healthy hypocotyls, cotyledons, and growing points. In soybeans, the growing points are above ground at emergence and are exposed after the cotyledons open. Freezing of all growing points is fatal. However, soybeans can compensate better for partial stand losses than corn.


Soybean cotyledons damaged by frost.
The hypocotyl (stem below the cotyledons) is damaged, so this plant will not recover. Photo: Luke Schulte

Management Moving Forward

Frost damage is often visible immediately. Assessment to occur damage should occur three to four days after the frost event when plants have had an opportunity to show new growth.  During this field scouting, if a significant portion of the stand is not showing signs of recovery, you may need to consider replanting. Your local Beck’s Representative can provide more information about evaluating a stand for replanting, and the Beck’s 100% free replant policy.

An early frost can have an impact on grain yield, but the trade-off between planting date impact on yield is generally greater than the frost damage impact on yield. Delayed planting further impacts profitability due to management delays, and higher harvest moisture and increased drying costs with corn.


Frost damaged corn field showing desiccated damaged tissue and green new growth. Photo: Jim Schwartz

 

Michael Blaine | Field Agronomist 

 

CLICK HERE FOR A DOWNLOADABLE VERSION OF THIS AGRONOMY TALK UPDATE

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