Cold Damage to Small Grain & Corn
April 21, 2021
With temperatures dropping tonight, we have an advisory update from Wade Thompson, Professor/Grains Specialist for Virginia Tech, to discuss potential impacts.
"I’m sure the upcoming forecast is generating some questions about the potential for frost/freeze injury.
First, let’s deal with corn. I don’t think any parts of our state are forecast to be cold enough to kill any young corn plants. Air temps would have to fall below 28 degrees or so for several hours for there to be a danger of plant death. What’s a lot more likely is that we get 32-35 with no wind and get a significant frost. For corn that is emerged, this may well result in death of those frosted leaves. While this will set the crop back, it should not harm the stand and plants should recover. After about three days, the growing points of plants can be examined for injury. Green, healthy tissue is a sign that plants will recover.
Purdue has a good, brief summary with photos. https://www.agry.purdue.edu/ext/corn/news/timeless/FrostedCorn.html
Based on the cool weather and rainfall, I have been expecting to see lots of nitrogen, sulfur and zinc deficiency early in this year’s corn crop. Cold injury may exacerbate this and bring those symptoms on even earlier. If deficiency symptoms do appear, an earlier than normal sidedress application may be needed this year.
Wheat is also a concern. The best resource that I know of on the subject comes from Kansas State. https://www.sunflower.k-state.edu/agronomy/docs/c646_Whole_Wheat_Freeze_Publication.pdf
The table below is from that publication and shows that temperatures around 30 degrees can definitely cause damage to our crop based on the growth stage of many fields. But note that these expectations for injury are from two hours of exposure to that temperature, not just a few minutes.
Like with corn, it will take 3-5 days after the event to assess the damage so I would encourage you and your growers to scout for injury next week."