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Determining freeze injury in wheat

Wheat freeze injury

CENTRAL PLAINS: Seems like we are having a real winter in Kansas this year. Driving past some wheat fields the other day, it was fairly difficult to detect that wheat had even been drilled in some fields. Consequently, many of the growers I have visited recently seem to be seeking a little reassurance that the wheat is OK.

Truthfully, it’s nearly impossible to walk into a field right now and determine the health of the crop. Soil temperatures have remained cold enough up to this point that if injury symptoms were present, it’s likely they won’t have appeared yet but there are four things you can consider while you wait for warmer weather:

  1. Acclimation – This is likely the most important variable. Allowing the wheat to acclimate to cold temps gradually and minimizing large temperature swings during the winter will greatly increase the winter hardiness of the plants.
  2. Moisture availability – Soil moisture helps in a couple of ways. Healthy plants with adequate moisture will have better cold tolerance, and soil moisture can also slow the penetration of cold air into the soil.
  3. Nodal root development – The plants will have better tolerance from the cold if they have developed nodal roots giving themselves more access to soil moisture and nutrients.
  4. Depth of the cold temps – How deeply sub-10-degree temperatures penetrate the soil is a critical element. If soil temperatures at the two-inch depth begin to fall below 10 degrees for an extended period of time, the likelihood of seeing winter freeze injury can increase substantially, even with adequate moisture.

Why can’t we see the damage now? Visually with the naked eye, the damage is detected by poor regrowth and discoloration in the crown tissue. It’s been too cold to observe regrowth or discoloration at this point. Discoloration is caused by bacteria and/or fungi attacking the damaged tissue, and these organisms are not active enough in the cold soil for the infections to be apparent. Thus, we need the temperatures to moderate a bit to detect the damage.

Want to know right away? Although not surefire, you can bring some samples inside, and green them up yourself. Keep the soil intact and try not to damage the plants. Store them at room temperature with adequate sunlight and moisture. After four to five days, you should see the leaves start to grow upright.

Continue to monitor growth for another week. Damaged plants with well-developed roots can green up initially, before going backwards. After that time, you can even go further and pull some plants for inspection. Just rinse them in cool water, lay them out on a towel and cover them with a damp (not wet) paper towel. Once the paper towel is dry, inspect the crowns for any red, brown or black discoloration. If the roots near the base of the crown remain white and the crowns remain translucent to pale-green, this is a good sign!

Again, this is not a surefire method for detecting damage. Plants with only minor damage can green up, and even then discoloration isn’t guaranteed to be present. However, minor damage provides an opportunity for infections to grab a toehold. Then, when stress occurs later in the season or conditions favor disease development, that toehold could lead to a foothold or eventually even a stronghold resulting in significant yield loss. So, even fields that begin to green up nicely this spring can sometimes go backwards later in the growing season.

All photos are the property of Syngenta unless otherwise noted.

Reporting from Viola, KS

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