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

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.

For wheat that has not reached jointing, temperatures of 12°F or below for 2 or more hours can cause damage.

For wheat that is at the jointing growth stage in areas that temperatures dipped to or below 24°F for at least 2 hours (Table 1) damage is likely.

Table 1. Low temperatures and duration that temperatures were 24F or less for selected KY counties Feb 26, 2017 mtidnight to 8:00 am. Data obtained from kymesonet.org.

To assess wheat freeze damage:

Wait until high temperatures are at least 40°F for 5 to 7 days.
According to the projected weather forecast, we will have high temperatures greater than 40°F all week, therefore assessing freeze damage Thursday or Friday will likely provide an estimate of freeze damage.
Scout fields and look for yellow, chlorotic growing points and limp leaves.
There will likely be yellow leaf tips, but as long as the growing point is not affected, there will likely be minimal to no damage.
Heaving is another concern this year for wheat stands and yield potential.
The extreme temperature changes we are having this winter could push wheat plants out of the soil. This can result in reduced stands and ultimately affect yield if heaving occurs on a large percentage of the field.

If you suspect or know your wheat was at jointing prior this weekend it will be important to assess for freeze damage even for areas that may not have been at or below 24°F for 2 or more hours.

More information on assessing freeze damage is in the Comprehensive Guide to Wheat Management in KY.