Search IPCM Newsletter Archives
Vol. 17, No. 6
Article 5 of 6
April 20, 2007
|
Fate of wheat crop may take until week's end; corn, too, may have been injured by frosts By Greg Horstmeier COLUMBIA, Mo. - Missouri's frosted crops need to revive before they will reveal the extent of damage from the Easter weekend's record low temperatures. "We need warmer temperatures and some sunshine before plants will regrow, and we can see how much damage was done," said Bill Wiebold, University of Missouri Extension agronomist. Wiebold and other MU crop experts discussed damage during a weekly teleconference, April 11, with extension specialists from around the state. Most specialists reported area wheat fields were showing frost-damaged leaves. While only a fraction of the state's corn crop has been planted, it too may have been damaged by temperatures that caused soils to freeze down to a 2- inch depth in places. Plant stems and leaves turned dark and limp due to the heavy frost, Wiebold said. This indicates cell death, and the affected portion of plant will not survive. "Patience is essential," he said. "We need some heat units for the damage symptoms to show up." He suggested specialists and farmers wait until the end of the week, which promises some chance of sunshine, before trying to assess the fate of fields. Wheat, typically a frost-hardy crop, was in an extremely vulnerable condition, Wiebold said. Near-record warm temperatures in March pushed the young wheat plants to grow ahead of schedule. Plants were well past jointing in central and south Missouri. Jointing is the stage where the stem begins to elongate, and the immature head is pushed above ground although still hidden by the leaves. "Minimum temperature records were set throughout the state during the April 8-9 weekend," said Pat Guinan, MU Extension climatologist with the Commercial Agriculture Program. "The state witnessed an unprecedented climatic event over a three-week period when an unusually warm two-week period beginning March 21 abruptly transitioned to a record six-day cold wave beginning April 4," Guinan said. A map of low temperatures for the weekend shows a smattering of 17- to 20-degree temperatures, deadly to tender crop plants. Only the Bootheel region was spared lows 20 degrees or lower. To check wheat spikes, or the stem containing the tiny, immature wheat head, Wiebold said to slit the main plant stem from the soil to the tip. When healthy, the tiny wheat head and nodes will appear white to light-green and be firm and moist. Damaged heads and nodes will appear dark and mushy. Corn fields also were in a vulnerable stage. At this point in the season, corn that has been planted and emerged has its growing point one-half inch or so below the soil surface, Wiebold said. Freezing temperatures below that point could likely have killed the growing point. Sprouted, but not yet emerged, corn kernels could also have been killed in soil that froze into the 1- to 2-inch depth. Wheat has secondary tillers that, if they survived, can produce wheat heads, though yields will not be as high as from the primary spike. Corn has no secondary, or "backup," growth point. As with wheat, Wiebold recommended waiting a few more days for temperatures to get back to more normal conditions, then checking corn plants and sprouted seeds for the mushy, dark appearance that signals plant death. Source: Bill Wiebold, 573-882-0621
Greg Horstmeier |
