Plant Diagnostic Clinic and IPM coordinator
Freeze injury is a possibility for our winter wheat crop given our very recent weather. The amount of injury or lack thereof will depend on a number of weather factors and crop growth stage. Wheat growers in our area will want to go out and scout their fields for possible injury.
Our University of Illinois Extension Agronomist Dr. Emerson Nafziger notes that "how well the wheat crop can tolerate temperatures dropping from highs in the 70s to lows in the 20s depends on crop stage and on how fast the temperature drops. Young, actively growing leaf tissue is vulnerable to freeze damage or death, but if the temperatures drop over two days or so, the leaf tissue can physiologically adjust to some extent, perhaps enough to escape serious injury. Wheat does not do this as well as bluegrass in a lawn, but it has much more ability to tolerate low temperatures than does a crop like corn". So that gives growers some reason for hoping the damage will not be substantial.
Environmental factors can also influence the amount of damage to a field. Dr. Nafziger indicates that "in the case of freeze injury in wheat, there can be large differences in damage based on things like cloud cover, how fast temperatures drop, how long they stay low, and even how much the sun shines on the days following cold nights".
Growers in our area of the state, and further north, are much less likely to be affected than wheat growers south of the I-70 corridor. This is because our wheat is at an earlier growth stage than down south where growth stages are reported to be at Feeke's Growth Stage 6 or up to jointing.
Freeze damage should show up within a day or two of the damage. Symptomology for wheat that is in the tillering stage will include yellowing leaves, leaf tips that appear brown or burnt, and the field may have a bluish cast or smell like silage. As severe as these symptoms sound, generally for wheat in these early growth stages yield impact should be minimal. If the wheat has gotten to the jointing stage symptomology from freeze damage will be more dramatic. If you split open the stem you will see death of the growing point, leaves will be yellow and again burnt in appearance. The plants may be bent over and the field will have a silage smell. Yield loss with these symptoms will be severe.
To aide you in identification of spring freeze injury in winter wheat there is an excellent resource from Kansas State University 'Spring Freeze Injury' with accompanying photographs that can help you in your scouting observations available on the web at http://kscroptests.agron.ksu.edu/pdf/SpgFrze.pdf.