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Frost Damage (06/03/21)

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During the early morning of Friday May 28, 2021, frost occurred in many parts of North Dakota and northwestern Minnesota. Temperatures below 32 F will cause water in plant cells of susceptible crops to freeze and resultant ice crystals will kill cells by damaging cell membrane systems. How different crop species react to freezing temperatures depends on where the growing points are, and if the cells have built in anti-freeze systems to prevent ice crystal formation.

Environmental conditions before or immediately after a low temperature greatly influence the extent of freezing injury. If the temperature drop is gradual, plants are in better condition to resist injury and can stand surprisingly low temperatures. Similarly, slowly rising temperatures after a frost and satisfactory soil moisture conditions are desirable to aid recovery. However, drought conditions, wind, and high temperatures are likely to aggravate frost injury and lessen the chance of recovery.

Corn plants less than 6 to 8 inches tall (five-leaf stage or less) will recover from frost because the growing point is still below the soil surface and is usually not damaged. However, in some plants the damaged tissue may constrict the emergence of a new leaf.

Cereal grains may lose some leaf tissue due to frost. New growth will occur after frost damage since the growing point is protected below ground before jointing.

Soybean and dry bean are quite sensitive to frost. Soybean and dry bean plants may leaf out again after a light frost from axillary buds in the leaf axil, where the cotyledon or the unifoliate leaves and the stem meet. However, tissue damage below the cotyledons will result in plant mortality.

Photo 1: Soybean frost damage. Picture taken Noon May 28, 2021, after early morning frost. and Photo 2: Soybean frost damage. Several plants died, some survived. Picture taken June 1, 2021, four days after early morning frost.

In evaluating frosted seedling fields, consider the percentage of plants killed and the percentage recovered. The surviving plants should be evenly distributed in a field. Even if many of the seedlings in a reasonable stand are frost killed, the field will usually produce more seed when left rather than if re-seeded, especially during the current drought conditions. The surviving plants will take advantage of the reduced competition for light, moisture and nutrients, and grow larger, producing more branches, pods and seeds per pod, thereby compensating for the lost plants. The remaining plants may require five to eight days longer to mature; but a re-seeded crop will require an even longer period to reach maturity.

 

Hans Kandel

Extension Agronomist Broadleaf Crops