With the cold temperatures the last few days, especially dipping below 20 degrees recently, there is certainly potential damage to our wheat crop in Southern Illinois. I want to stress that at this point I am only saying POTENTIAL damage. It is far too soon to tell for sure. Attached are links to documents from the University of Tennessee and the University of Kentucky that do very nice job describing freeze injury to wheat. A hard freeze like we just experienced can be damaging to heads as well as stems. As you read the UT bulletin, please remember that their wheat crop is ahead of ours from a growth and maturity standpoint, so what you see there does not mean it will happen here in SIL. That said, we certainly need to recognize the potential for damage in our area as well.
Of course, the potential injury depends on many factors, including growth stage, the actual low temperature reached, the duration of the low temperature, and the soil moisture under the wheat canopy. The most important being the growth stage of the crop and the low temperature reached. At Feek’s stage 6 wheat has begun to joint and this is the first point at which the head size is determined and most susceptible to injury. Much of our Southern Illinois wheat was slightly behind this stage (Feek’s 6) and was currently at Feek’s 5 as of late last week. However, due to the above average growing conditions both in the fall and through February this spring, I suspect we have some fields already at F6 and potentially some later than that. For those fields, this cold snap, and especially last night’s freeze will have the greatest impact.
Last night’s temperatures dipped below 20 degrees in some areas, and that 20 degree mark is where we start to see potential issues if temperature stays that low for more than a couple hours. We did have high levels of soil moisture which will help keep the ground temperature from falling quite so fast so that will certainly help. The snow Saturday and Monday will also help keep temperatures at the growing point from dropping so suddenly.
We are obviously right on the verge of potential damage, but again it is too early to make that call. I will not begin looking at our wheat until next Wednesday to determine potential damage. At that point I will send more information on how to determine potential damage and properly stage the wheat. Until then, you can scout your wheat fields and at least determine what stage they are at, that will give you an idea of what COULD be ahead. The easiest way to identify fields with the highest potential damage is to determine if the flag leaf is out. If that is the case, these fields will have the highest potential for injury. If you can’t identify the flag leaf yet, and there are no visible joints on the main stem, the potential for damage is greatly reduced, and that is a very good sign. In fields at this growth stage and between first joint and flag leaf emergence, we will wait about a week to take a look at possible damage and determine severity. I have attached a document on identifying wheat growth stage. As always, please call with questions and we can discuss. We will hope for the best and take a close look next week.