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.

Canola Freeze Injury

Flowering canola plant. Princeton, KY. 21 Mar 2016.

Carrie Knott, Extension Agronomist-Princeton, University of Kentucky

Quite a bit of information for winter canola freeze injury exists (see the end of the blog for links).

This past weekend, most of the state remained in the low-30s°F. Weather data can be found at: wwwagwx.ca.uky.edu or www.kymesonet.org.  At these temperatures significant damage, even to flowering canola is not expected.  The critical temperature for winter canola is mid- to low- 20s°F. 

Freeze Damage on Winter Wheat

Chad Lee and Jim Herbek, Extension Agronomists, University of Kentucky

The cold temperatures experienced yesterday in many areas and the cold temperatures expected tonight could damage the wheat crop. Wheat in the boot or heading stages generally needs temperatures at or below 30 F (-1.1 C) for at least two hours to cause severe damage. The Kentucky Mesonet reported lows of 45.1 F for Fulton County, 38.0 F for Graves County, 41.1 for Hopkins County, 42.7 F for Simpson County, and 39.6 F in Mercer County) for Sunday, May 12, 2013. None of these temperatures are low enough to severely damage wheat, but localized temperatures across fields may have been lower. 

Bleached wheat head exhibiting freeze

damage symptoms. Photo taken in 2012.

Usually, a week to ten days of warm, sunny weather is needed before the full extent of a freeze damage becomes evident. So, while we all want to scout fields today and tomorrow, a true assessment of freeze damage should not occur for about a week. Cool, cloudy days will slow wheat growth and slow the development of freeze symptoms.

Winter Wheat and Potential Freezing Weather

Chad Lee, Extension Agronomist, University of Kentucky

Recent weather forecasts include the potential for temperatures to dip into the low 30's or upper 20's (Fahrenheit) for the next couple of days. Much of the wheat around Kentucky is somewhere between the boot stage and heading, which means temperatures around 28 to 30 degrees could cause damage.

Wheat sensitivity to cold temperatures depends on the growth stage (Table 1). If a freeze event occurs, the wheat will need about a week to ten days of good growing conditions before we can assess damage. At that point, we will need to examine the developing heads for noticeable signs of damage or death, the stem for signs of girdling (which could lead to lodging) and the tillers which could produce viable heads.

Corn Planting this Spring

Chad Lee, Extension Agronomist, University of Kentucky

Young corn plant killed by freezing temperatures. 

The weather is warm, the soil is warm, the redbuds are blooming... it seems like we should be planting corn! Some producers have sprayed their burndown herbicides, which is a good thing this season considering how large weeds could get. Some have finished applying anhydrous ammonia, which is good because soil conditions are good. Now that these major tasks are done, all that is left is to plant corn. The fields are ready, but the calendar is not.



Last season, the rains came in early and stayed late. Every farmer was pushed to get corn planted at all, let alone in a timely fashion. Late plantings, especially on soybeans did better than "early"plantings last year. The calendar says late plantings hurt yields. This spring, something internally says that everything else is ready, let's plant some corn! The fresh memory of the previous planting season says let's plant some corn! But, the calendar says not to plant corn, yet.