Assessing Spring Frost Damage in Corn and Soybeans


New corn growth following frost damage.

Each year, late spring frost is a concern in most corn and soybean growing areas. Crops planted early are at a greater risk because early establishment exposes plant growing points earlier in the season, which makes them more vulnerable to damage. 

In this article, we’ll review factors that increase frost severity, symptoms of frost injury and how to determine if a plant will survive. Finally, we’ll look at decision points for managing frost-damaged crops.

Factors Increasing Frost Severity

  • Air temperature drops below 32° F
  • Length of time below freezing
  • Growth stage of crop
  • Wind speed (calm nights)
  • Cloud cover (clear nights)
  • Topography (low areas of field)
  • High soil residue (cooler soils) 

Symptoms and Determining Surviving Stand
Freezing temperatures do not necessarily cause crop injury. While temperatures of 28-30° F or below can cause frost damage, there are multiple examples of 28° F not causing significant damage or stand loss. Remember, the length of time below freezing is a factor; temperatures must be at or below freezing for more than a couple hours to cause damage. Additionally, microclimatic conditions such as air movement (wind), cloud cover and topography can increase or decrease risk of frost within local areas. 

Frost-damaged plants will appear darker in color within the first few hours of freezing. If the damage is less severe, they may look water soaked. Over the next few days, plants will begin to appear browning and necrotic. 

Determining the survival of corn is highly dependent on the growth stage the plant was in at the time of freezing. During normal plant development, the growing point of corn remains below the soil surface until V5-V6 growth stages. Due to the depth of the growing point, newly emerging plants are at less risk of injury than V3-V4 plants, where the growing point is nearing the soil surface. During short periods of air temperature drops, the soil acts as a buffer to maintain the growing point temperature above freezing. 

Frost damage will lead to the loss of upper leaf area, but warm growing conditions soon after will result in new growth emerging from the whorl of the dead tissue. Prior to new leaf growth, corn survival can be gauged by digging up plants and cutting open the stem to evaluate the growing point. Dark yellow to brown growing points could indicate severe damage and a plant that is less likely to survive. 

Soybeans can survive slightly cooler temperatures than corn. However, the growing points of soybeans are exposed above ground as soon as seedlings emerge from the soil. Each developing node becomes the predominate growing point for soybeans. Soybeans with frost injury to upper nodes can still survive. If lower canopy temperatures remain above freezing due to leaf coverage and soil warmth, soybeans will begin regrowth from lower surviving nodes. 

Left: Lightly frosted corn plant with watersoaking and necrosis

Right: More severe frost injury with protected growing point and new leaves appearing from whorl days after frost

Decision Points for Managing Frost-Damaged Crops

  • Wait 2 or more days after frost occurrence before evaluating regrowth or growing point health to determine the number of surviving plants remaining.
  • Consider calendar date and potential yield reduction a replanted crop may encounter.
  • Weigh yield potential of reduced stand against yield potential of a later planted crop.
  • Consider additional costs of replanting such as seed, fuel and labor expenses.
  • Refer to the Golden Harvest Online Replant Calculator as an online resource for corn.
  • Final soybean stands near 100,000 plants per acre or greater likely will not need replanting.

An alternative management practice is clipping the damaged leaf area to speed recovery. Many farmers and researchers have played with cutting off frost-damaged tissue to allow for regrowth to occur more easily and quickly. This method is usually only considered for corn at V5 or larger as a method to remove damaged tissue. Due to growing point emergence occurring at the same time, take caution to avoid damage when clipping plants. University research shows mixed results with this management practice and indicates grain yield loss as a consequence of clipping. Clipping plants should be reserved for severe cases where you are certain plants will not survive without taking action.

Reacting quickly after frost can often be farmers’ first response. Unfortunately, this situation will require patience and investigation in order to determine the impact. Getting a good idea of the number of surviving plants will be the most critical decision factor. Allow plants the chance to recover before making a final determination. 

Before taking action and to get a second opinion on affected fields, contact your local Golden Harvest Seed Advisor.

Photos are either the property of Syngenta or used under agreement.
Syngenta hereby disclaims liability for third-party websites.


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