By Jason Kelley, Wheat and Feed Grains Extension Agronomist
Wheat freeze damage from the morning of March 15th 2017 is becoming more evident across eastern and Northeast Arkansas. Overall the level of damage appears to be less than anticipated given the low temperatures and growth stages. I have not seen any fields or heard of reports of fields with what I would consider having severe damage. The full extent of damage will become clearer in the coming days and weeks.
Below is a description of several types of freeze damage that we are currently seeing:
Leaf burn is the most common and most easily recognizable injury symptom that is being seen (Figure 1 below). The leaf burn in the photo was from an area where the temperature dropped to approximately 27 degrees F. Leaf burn itself should be considered cosmetic injury, but it does indicate that temperatures were cold enough to potentially cause other forms of damage including head and stem damage and further investigation is needed to verify any damage.
Head damage is also being seen on a limited basis across Northeast Arkansas. Figure 2 (Photo by Chris Elkins, Poinsett Co.) shows a white and dead head on an otherwise healthy looking plant. Dead heads like this were probably not noticeable earlier in the week and will become more evident in the coming days. This kind of damage seems to be found mainly on the largest tillers and at this point appears to be limited.
Stem damage is another form of damage that may be seen. Temperatures were cold enough in some areas that stems froze. A very few ruptured lower stems have been found,. Stem damage can be found in several forms, but a soft, rubbery or flat spot on the stem typically between the first and second or second and third nodes is often seen. The photo in Figure 3 shows a stem that is soft and rubbery and the tiller will eventually die. Non-lethal stem damage that does not kill the tiller and head may cause the stem and or nodes to be brittle and could increase lodging potential later in the season near harvest.
Damage to emerging heads on very early maturing and/or very early planted wheat may show different symptoms than described above. We had a very limited amount of wheat that was in the boot/heading stage when it froze last week. The head for the most part does not show damage, but closer examination shows that the flower portion of the head was damaged. Anthers should be a light green color prior to emerging. If anthers are white or a light brown prior to emergence, the anther was likely killed and the floret will be sterile, Figure 4.