Assess Wheat For Freeze Injury

Thanks to Mother Nature’s somewhat cruel sense of humor, farmers in wheat-growing states need to evaluate their stands for death from recent (and upcoming) cold snaps. Damage will vary depending on what varieties you used, what stage of growth the plant was in and how long it stayed cold.

Don’t go out to assess injury immediately, according to Oklahoma State University (OSU) research. Signs and symptoms of damage might not be noticeable until days later.

If warm temperatures return quickly you should wait about a week to check. Whereas if temperatures remain cool after the freeze event it might take up to two weeks before you can accurately assess injury. Based on forecasts across much of the Midwest, most farmers will need to wait two weeks.

OSU shows a few injury symptoms in which you should be aware:

  • Yellow and necrotic leaf tips are often a cosmetic injury that appears after a freeze, but it might not affect yield.
  • If the entire leaf turns yellow to white and the plants are limp with a slight “silage” smell, that’s more severe damage that could affect yield.
  • Check the growing point for injury, yield loss could be more severe if it’s damaged. Slice the stem lengthways and look for a crisp, whitish-green, turgid growing point. If it’s mushy, limp, brownish colored and breaks off when lightly flicked it’s injured. Another sign the growing point was injured is if the emerging leaf is necrotic.

Temperatures that Cause Freeze Injury at Various Stages

Growth Stage

Approximate injurious temperature (2 hours)

Primary Symptoms

Yield Effect

Tillering

12° F

Leaf chlorosis, burnt leaf tips, silage odor, blue cast to fields

Slight to moderate

Jointing

24° F

Growing point death, yellow or burnt leaves, lesions, lower stem split or bent, odor

Moderate to severe

Heading

30° F

Floret sterility, white awns or white spikes, damage to lower stem, leaf discoloration

Severe

Flowering

30° F

Floret sterility, white awns or white spikes, damage to lower stem, leaf discoloration

Severe

Milk

28° F

White awns or white spikes, damage to lower stems, leaf discoloration, shrunken, roughened or discolored kernels

Moderate to severe

Dough

28° F

Shriveled, discolored kernels, poor germination

Slight to moderate

Source: Kansas State University

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