Did Freezing Temps Affect Wheat?

The cold temperatures on the morning of May 18 have a some questioning whether there will be any effect on the wheat crop. Based on reports from area weather station the lowest recorded temperature was 34 for Toledo, 35 for Wauseon, 36 at OARDC NW Ag Research Station and 37 for Napoleon,& Defiance. The coldest temps lasted for about 1 hour based on hour by hour data from OARDC NW Ag Research Station. The current CORN Newsletter address wheat development and cold temperatures. Based on this information it would seem we have little concern of injury in wheat from the cold temperatures Monday morning.

Air temperatures dropped to an average of about 35 degrees on at least two nights over the past week. Understandably, some wheat producers are concerned that these relatively low temperatures may have caused some damage to their crop. Thirty-five degrees is really not a problem, however, we do not know what temperatures the wheat head actually experienced. We will have to see what happens over the next few days. At our current growth stage, between Feekes 9 and 10, in northern counties and between heading and flowering in southern Ohio, the yield effect of frost can range from moderate to very severe if temperatures drop to 24 - 28 F for two or more hours. It all depends on the variety, the growth stage, how cold it was, and the length of time plants were exposed to the cold temperatures. The amount of damage is a function of both time of exposure and the temperature, but no one has any numbers that we know of. We just don't know. For example, 28 degrees for 30 minutes may be as bad as 31 degrees for a long period.

Freezing temperatures between boot and flowering may cause spikes to be trapped in boot, leaf discoloration, floret sterility, and damage to the lower stems. The damage tends to be most severe with the greatest yield impact between heading and flowering. The head has some protection from cold temperatures until it emerges, but is easily damaged after emergence. Sterility and stem damage may lead to yield loss, however, since it is highly unlikely that all the plants in a field were at the same growth stage and were equally exposed to temperatures below 30 F, the overall damage may be minimal and restricted to low areas of the field. At most there may be some leaf tip burn on more sensitive varieties. Wheat is a winter crop and can tolerate cold temperatures.

The visual symptoms of frost injury to the heads appear as bleached glumes (and can be confused with scab or take-all). Additionally, freeze damaged florets appeared to be lighter green in color than unaffected florets on the heads. Remember, you can not detect damaged fields from the roadway; you will need to walk the field and inspect individual heads to see if there is any damage.