Early Spring Freeze Effect on Kentucky’s Wheat Crop

By Conner Raymond, Matthew Dixon, Dr. Carrie Knott

Even though we have officially made it to spring in Kentucky, we are not exempt from sub-freezing temperatures. From March 26 through March 28, large portions of the state experienced temperatures that lingered around the threshold that could significantly impact wheat yields. The majority of the state is around the Feekes 6-7 growth stage or jointing. At this stage the growing point of the plant is above the soil surface and is particularly sensitive to temperatures at or below 24°F for periods of two hours or more. Even though temperatures fell below the threshold that does not necessarily mean damage has occurred. Thanks to Matt Dixon, Senior Meteorologist in the UK Biosystems and Agricultural Engineering department, we can see that across the largest wheat producing counties in Kentucky, only six Mesonet sites were below the 24°F threshold and of those counties only four sustained that temperature for more than two hours (Brandenburg, Cynthiana, Maysville and Stanford).

According to Matt Dixon "Looking ahead, models suggest low temperatures in the 30s this weekend (April 9-10). Some may approach freezing, but nothing concerning in terms of the winter wheat crop. Long range outlooks then favor above normal temperatures next week (April 11-17). Normal low temperatures for the midsection of April run in the mid to upper 40s, while highs average in the upper 60s to low 70s. This would put most of the major wheat-growing areas past the average date of last spring freeze (below). Good news, although, we've seen some late freezes in years past.”

After a significant freeze event it is vitally important to scout wheat fields for damage. Typically, damage to heads and stems can be seen seven to ten days after a freeze if the plant has been ACTIVLEY growing with good conditions above 40°F and adequate sunlight. If conditions are cool and cloudy, more time may be needed to assess damage to plants. According to the AGR 253 Identifying Damage and Estimating Yield Reductions following a Spring Freeze in Winter Wheat, primary symptoms of damage at this growth stage include death of growing point, leaf yellowing or burning, lesions, splitting or bending of the lower stem and an odor. When assessing damage to heads, carefully peel back layers of leaf sheaths at the highest most node on the plant to reveal the un-emerged head. Once the head has been revealed, an undamaged head appears green glossy and turgid opposed to a damaged head which will be white or tan, shrunken, limp or brittle. For more information regarding freeze damage on wheat, refer to AGR 253 Identifying Damage and Estimating Yield Reductions following a Spring Freeze in Winter Wheat.