OPTIONS FOR FREEZE DAMAGED WHEAT: WHICH WILL BE MOST PROFITABLE?

 Greg Halich, Extension Economist, University of Kentucky

A severe freeze in mid-March has likely damaged much of the wheat crop in Kentucky. The extent and severity of the damage will be better known one to two weeks after the freeze when baseline estimates can be made. Normally, producers would have three options to deal with wheat stands that have been damaged at this stage:
1) Stay the course, harvest the wheat and then double-crop soybeans.
2) Terminate the wheat stand and plant corn.
3) Terminate the wheat stand and plant full-season soybeans.

Varietal Differences in Freeze Damage

Dave Van Sanford, Wheat Breeding and Genetics, University of Kentucky and Bill Bruening, Small Grain Variety Testing, University of Kentucky
The wheat varieties we grow in KY will respond differently to the extremely low temperatures we have experienced over the past few days. Several traits come into play but the most important thing

for the grower to consider at this point is growth habit, which can range from completely prostrate to very upright.

Most of the wheat varieties grown in KY develop at a rate that is determined by heat units accumulated, which we commonly refer to as Growing Degree Days (GDD). These varieties were pushed by the unusually warm temperatures we experienced in February, so that many of them had reached jointing (Feekes 6) or beyond when the severe freezes began. A much smaller percentage of our wheat varieties are held back by sensitivity to daylength. These daylength sensitive varieties will not joint until they reach a daylength threshold – i.e. a minimum no. of hours of daylight. Such sensitive varieties remain prostrate in their growth habit until the threshold is reached and thus the growing point remains near the soil surface and is much more protected than the growing point in an upright variety at jointing or beyond.

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:

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.

Freezing Temperatures Overnight May Damage Winter Wheat at Advanced Growth Stages in KY

Figure 1. Wheat heads showing freeze
damage at heading (Feekes 10.5)

Carrie Knott, Extension Agronomist-Princeton, University of Kentucky

Last night temperatures dipped to or below 24°F for several hours at many locations throughout Kentucky (Table 1). For winter wheat that has reached the jointing (Feekes 6) growth stage, damage (Figure 1) can occur to the developing wheat head, which is above the soil surface at jointing, when temperatures are 24°F or below for at least 2 hours.

Wheat Injury Unlikely Despite Unusually Cold Temperatures

Carrie Knott, Extension Agronomist-Princeton, University of Kentucky

Most of the wheat crop in Kentucky is either still tillering (Feekes 4-5) or just beginning to joint (Feekes 6). Although this has presented management challenges this year, it also may have protected the crop against freeze injury from the unusually cold temperatures the past two nights.

Wheat Freeze Damage

Carrie Knott, Extension Agronomist-Princeton, University of Kentucky

Record low temperatures with little to no snow cover last week may have caused some damage on the wheat crop in Kentucky.