RAPID CITY, S.D. - Average frost dates in the higher elevations of western South Dakota run into mid-May, but this year a freeze occurred close to the final edge of that average in several locations across South Dakota.
With the otherwise warm temperatures throughout the early parts of spring, the cold spell caught winter wheat fields that looked promising for high yields.
Charlie Boe, local agronomist for several farmers in south-central South Dakota and north-central Nebraska, says the freeze damage is hard to detect until the crops grow further.
In wheat heads, the anthers, or male parts inside the floweret, can be damaged by frost. When they wilt, the floweret becomes sterile and heads won’t fill, and that’s when producers will be able to visualize the damage, if any.
Boe says the full extent of the damage of the May 15 freeze for most farmers won’t fully be known until combines hit the fields.
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The National Weather Service says the frost hit the western edge of the state - Buffalo to Rapid City - and into northeastern South Dakota from Aberdeen to Brookings. The temperature hit 26 degrees or lower for three to four hours, which was low enough to damage several types of unprotected plants.
Boe says the temperature, length of time below freezing and plant size are calculated together to determine probable loss.
Wheat can tolerate 24 degrees Fahrenheit in the joint stage and 28 degrees Fahrenheit in the boot stage, but a light frost could hurt flowering or heading plants. Most of the winter wheat he sees now was in the boot stage when temperatures dropped to 26 degrees Fahrenheit or lower.
There were other crops that might be affected by the mid-May frost, too.
Boe says some corn froze, but fields he observed only showed one or two leaves above the ground, so he anticipated it will come back. Corn that had more leaves above ground might curl up and trap new growth.
There was also some observed damage to field peas and pulse crops, such as lentils.
While Boe hasn’t seen any replanting happening in his areas, he has advised some clients not to expect the high yields they might have hoped for.
Mother Nature has several curve balls to throw at crops in the fields this time of year. Frost in mid-May is just one of the unexpected weather events that can affect a farmer’s final yields.
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Boe recommends a publication for farmers interested in learning more about their particular fields called, “Spring Freeze Injury to Kansas Wheat.” The 12-page fact guide serves as a reference for Midwest farmers who want a more in-depth look at frost damage.
