Assessing Winter Wheat Freeze Damage

Carrie Knott, Extension Agronomist-Princeton, University of Kentucky
 

Last night temperatures dipped below 24°F for several hours throughout Kentucky. Winter wheat at the jointing (Feekes 6) growth stage, was likely damaged by these cold temperatures.

To assess wheat freeze damage:

 Figure 1. Healthy wheat head at the Feekes 6, jointing growth stage. 50x magnification.  Photo: Brenda Kennedy.

Figure 1. Healthy wheat head at the Feekes 6, jointing growth stage. 50x magnification.  Photo: Brenda Kennedy.

  1. Wait until high temperatures are at least 40°F for 5 to 7 days. According to the projected weather forecast, most of the state will have high temperatures greater than 40°F the next 7 days. Assess freeze damage next Tuesday or Wednesday. Any earlier than the middle of next week may provide an inaccurate estimate of damage.
     
  2. Freeze damaged wheat will have yellow, chlorotic growing points, limp leaves and/or a silage odor. There will likely be yellow leaf tips. This is a cosmetic problem only. The real issue is whether or not the growing point was damaged. A healthy growing point will be turgid, somewhat translucent and very glossy (Figure 1 and 2). A freeze damaged growing point will be limp and greenish is color. A hand lens is very helpful at differentiating these subtle differences.
 Figure 2. Healthy wheat head at the Feekes 6, jointing growth stage. 20x magnification.  Photo: Brenda Kennedy.

Figure 2. Healthy wheat head at the Feekes 6, jointing growth stage. 20x magnification.  Photo: Brenda Kennedy.

It is likely that the main stems, which are  at jointing, will be killed by last night’s and tonight’s low temperatures. The key is to determine the number of healthy tillers that remain. This will help determine the yield potential of the field and ultimately the decision to keep or destroy the wheat crop.

More information will follow once we understand the scope of the problem.