Ice-coated wheat, and symptoms of freeze damage
click image to zoomJim Shroyer, K-State Research and ExtensionWheat with a thick coating of ice in Saline County, April 11, 2013. In central Kansas, many fields of wheat were covered in a thick coating of ice on April 11. By itself, a coating of ice on the surface of leaves and stems will usually not cause direct damage unless the wheat is tall enough that the weight of the ice breaks the wheat over and causes lodging. Ice can also cause leaves to become water-soaked and mushy, but this will not affect new leaves.
Ice on the surface of leaves and stems doesn’t necessarily mean there will be ice inside the stems. Those are two separate issues. If there is ice inside the stems, that may or may not injure the developing heads. You might think ice inside the stems would always cause damage, but anyone who has seen a lot of spring freeze events knows that wheat’s response can be unpredictable.
There have been times when there was ice inside the stems, and it simply melted and the wheat had normal head development afterward. It may depend on how cold the temperatures were when the ice formed. Other times, ice will kill the heads or split open the stems, which usually results in severe injury. Oddly, even split stems do not always mean the end of the tiller. In 1997, there were a lot of split stems that surprised everyone by healing up on their own, due to the wet mild conditions in the weeks following the freeze.
click image to zoomJim Shroyer, K-State Research and ExtensionCloseup of ice on wheat. Unless the ice formed inside the stems or breaks over the plants, this in itself should not cause a problem. It may cause the leaves to become water-soaked, but new leaves should be fine unless the growing points have been killed. Where stems and/or growing points were killed by the freeze, start looking for new tiller growth coming from the crown area. In fact, look for new tiller growth even if you think the stems look okay. Sometimes tillers can be killed but will not show any symptoms for quite a while. In those cases, the first sign that the tillers are dead is the sudden growth of new tillers at the base of the plant.
There are many possible scenarios after a freeze, and things do not always go according to “the book.” So just keep watching your fields closely over the next 7 to 10 days for the following:
* The color of the developing head or growing point. As long as heads are light green and turgid, the head in that tiller is fine. If the head is whitish and flaccid, it has died.
* The color of newly emerging leaves. If they are nice and green, that probably indicates the tiller is alive. If newly emerging leaves are yellow, that probably indicates the tiller is dead. The color of existing leaves is not terribly important, except for the flag leaf. Existing leaves will almost always turn bluish-black after a hard freeze, and give off a silage odor. Those leaves are burned back and dead, but that in itself is not a problem as long as newly emerging leaves are green.
* The integrity of the stem. If there are lesions or crimps anywhere on the stems, that usually means the wheat will lodge at some point during the season. If the stems look undamaged, that’s a good sign.