Richard Taylor, Extension Agronomy Specialist; rtaylor@udel.edu
Since the unusually cold temperatures last week and with many fields showing at least leaf burn from the very low morning temperatures, I thought it might be worthwhile to include here some information from the University of Kentucky about freeze injury on wheat. Reprinted below is Table 1 from an article by Chad Lee and Jim Herbek, Extension Grain Crops Specialists with the University of Kentucky and originally printed in Wheat Science News, Vol. 11, Issue 1 for April 2007 and published by the University of Kentucky College of Agriculture Cooperative Extension Service. Wheat losses from cold temperatures depend on the growth stage of the wheat, the air temperature in the canopy, the duration of the temperature, and possibly the sensitivity of the wheat related to the amount of nitrogen (N) applied (the higher the N rate, the more tender the tissue). It is important for growers to scout frost-susceptible small grain fields to keep abreast of yield potential for their marketing plans.
Photo 1. Winter injured wheat showing leaf burn but this wheat had not reached the jointing stage.
| Growth
stage |
Approximate
injurious temperature (2 hours duration) |
Primary Symptoms | Effect on Yield Potential |
| Tillering
(1-5)a |
12˚ F. | Leaf chlorosis; burning of leaf tips; silage odor; blue cast to fields | Slight to moderate |
| Jointing
(6-7) |
24˚ F. | Death of growing point; leaf yellowing or burning; lesions, splitting, or bending of lower stem; odor | Moderate to severe |
| Boot
(10) |
28˚ F. | Floret sterility; spike trapped in boot; damage to lower stem; leaf discoloration; odor | Moderate to severe |
| Heading
(10.1-.5) |
30˚ F. | Floret sterility; white awns or white spikes; damage to lower stem; leaf discoloration | Severe |
| Flowering
(10.51-.5) |
30˚ F. | Floret sterility; white awns or white spikes; damage to lower stem; leaf discoloration | Severe |
| Milk
(11.1) |
28˚ F. | White awns or white spikes; damage to lower stems; leaf discoloration; shrunken, roughened, or discolored kernels | Moderate to severe |
| Dough (11.2) | 28˚ F. | Shriveled, discolored kernels; poor germination | Slight to moderate |
a Numbers in parentheses refer to the Feekes’ scale.