Freeze symptoms and associated yield loss in soft red winter wheat

In the soft red winter wheat (Triticum aestivum L.) growing regions of the eastern United States, midwinter warm temperatures have accelerated wheat development, exposing wheat that has transitioned to reproductive stages to cold temperatures during late spring. The objectives of this diagnostic guide were to: (a) provide images depicting freeze injury and (b) provide estimates of grain yield and straw biomass reduction in response to low temperature at the Feekes 6, 8, and 10.5.1 growth stages of soft red winter wheat. Wheat plants were transplanted from the field into pots at each the Feekes growth stage and placed into freeze chambers with temperature treatments ranging from 3 to 39 degrees F. Plants were then placed in an open-air greenhouse and grown to the completion of grain filling. Grain and biomass yield were evaluated and modeled across temperature treatments within each growth stage. Small temperature differences resulted in large differences in yield. At the Feekes 6 growth stage, grain yield was reduced by 10% at 17.9 degrees F and 25% at 14.8 degrees F. At the Feekes 8 growth stage, grain yield was reduced by 10% at 27.6 degrees F and by 25% at 24.6 degrees F. At the Feekes 10.5.1 growth stage, grain yield was reduced by 10% at 27.8 degrees F and by 25% at 26.3 degrees F. Our guidelines provide estimates for potential reductions in grain yield associated with low temperatures. However, scouting fields approximately 2 wk after the freeze event (and after active growth has resumed) is important, as there are microclimates within fields.