Assessing freeze damage in KS wheat
The repeated hard freezes in Kansas are taking a toll on some of the wheat furthest along in development, said Jim Shroyer, K-State Research and Extension crop production specialist. Temperatures were in the mid- to low-20s on the nights of April 23 and 24, which is low enough to damage wheat in more advanced growth stages, he said.
“This is the third episode of hard freezes we’ve had, starting April 9. This time, the freeze caught a few more fields in the jointing and pre-boot stage than the freeze on April 9 and 10. What should producers expect now? If freeze-damaged wheat heads out, will that head be viable and produce grain? It depends on what stage the wheat was in when the freeze occurred,” Shroyer said.
Jointing to pre-boot: If the tillers were in this stage or earlier at the time of the freeze and the tillers are green and growing actively now, then the heads should be fine. If the head had been killed, the tiller would not be green and actively growing. If the leaves coming out of the whorl are chlorotic, then the head on that tiller is dead.
Boot: If tillers were in this stage at the time of the freeze, there are several possibilities. The head may be fine, it may be partially damaged, or it may have been completely killed. In any of those cases, the head may continue to emerge.
If the head is fine, it will turn from lime green in the boot to a darker green when it emerges. If the head is freeze-damaged, some or all of the spikelets will become yellow and/or watersoaked in appearance as it emerges. It’s possible for some of the spikelets to be alive and a healthy dark green while other spikelets on the same head are damaged. If a spikelet flowers normally and the kernels on that spikelet develop normally, then the head is at least partially viable and can produce grain.
In southwest Kansas, irrigated wheat is probably going to have the most severe freeze injury, and some stands could be mostly or entirely lost, Shroyer said. Some of the dryland wheat in southwest Kansas, especially early-maturing varieties and wheat in low-lying areas also may lose some tillers -- or have even more severe damage in some cases, he added.
The freezes have caused extensive leaf damage in west-central and northwest Kansas, but some of that wheat is already greening back up, especially where the growing point was still at the soil surface or just slightly above the soil at the time of the freezes, he reported. Where tillers were killed, new tillers are beginning to grow in many cases, he added.
Freeze damage is not the only problem for dryland wheat in western Kansas, Shroyer said.
“Dry soils and mite damage are limiting the yield potential of dryland wheat in western Kansas as much or more than the freezes. The smaller wheat hasn’t been hurt much by the freezes except for leaf burn, but it will need some moisture to produce much grain,” he said.
In south-central Kansas, temperatures also got into the mid-20s on April 24. Some wheat had one or two joints at the time of the freeze, and this could cause some tiller loss, Shroyer said. The situation there is a little different than in western Kansas, he added.
“Soil moisture conditions are much better in central Kansas than in western Kansas. This will help reduce the severity of freeze damage to some extent, and will help the wheat regrow or continue to develop in the coming weeks,” he said.
“However, there are reports of freeze damage to the lower stems in that region. If the lower stem damage is severe, the wheat will eventually lodge,” he added.
More information on freeze damage to wheat is available in “Spring Freeze Injury to Kansas Wheat,” K-State Research and Extension publication C646, available at county and district Extension offices and here.
Editor's Note: This report was compiled by Steve Watson, Kansas State University Research and Extension.