2017 Wheat Freeze: Where’s the Damage??

Dr. Carrie Knott — Extension Grain Crops Specialist, Princeton

I doubt there has been a case where I have been so happy to say “I WAS WRONG!”.

Now that we have had a little more than a month since the 2017 freeze events, many –myself included– are left wondering: “Where is the damage?”

Most reports I am hearing throughout the state, from producers and county agents, are that there is very little, if any damage. There have been some reports of head death (Figure 1) and stem damage (Figures 2 and 3), but for the most part it seems most of the wheat was not affected by the freeze.

This is quite surprising given that all the literature indicates that temperatures below 24°F for two or more continuous hours cause death of the heads and stem damage to wheat. Many acres were examined for head injury in the last few weeks. There are some reports that heads were killed by the freeze, but only a small percentage of Kentucky’s total wheat acreage. In a couple of those cases, the stems continue to appear “healthy”; however there is no wheat head within the developing stem.

Figure 1. Developing wheat heads at approximately Feekes 6 (jointing) growth stage. Seven days prior to this photograph the developing wheat head on the left was damaged by temperatures less than 24°F for more than two consecutive hours. The developing wheat head on the right is healthy.

Wheat has also been examined for stem damage. There are more accounts of stem damage than head death. In most cases, stem damage is not severe, that is, the wheat still looks excellent from a windshield (Figure 4). However, regions of the stems are weaker than normal stems, due to the freeze. It is possible that these weakened regions of the stem will remain upright until grain fill and ripening. It may be at this point that stems will break and plants will lodge due to the additional weight of the grain.

Only time will tell whether weakened stems will remain intact until grain yield. For now, when scouting fields this season assessing stem health and lodging will be important to determine whether weakened stems may be at an increased risk of lodging prior to harvest.