AgEBB-MU CAFNR Extension

David Burton
Civic Communications Specialist
2400 S. Scenic Ave.
Springfield, MO 65807

April 20, 2018

Be Patient When
Assessing Cold Injury

LAMAR, Mo. - Jill Scheidt, agronomy specialist with University of Missouri Extension, scouted fields around Barton County April 11. She observed wheat at the second joint, and newly sprouted corn.

If wheat is jointing, moderate to severe damage can occur at temperatures at or lower than 24 degrees F for two or more hours. Symptoms include death of growing point, leaf yellowing or burning, lesions, splitting or bending of lower stem and odor.

"Identify the joint stage by running fingers along the stem, feeling for the first node," said Scheidt.

"To assess possible injury, carefully split stems open just above the growing point, which is the uppermost node, to expose the developing head," said Scheidt.

A normal growing point is bright white to tallow-green and turgid. Freeze injury causes the developing head to become off-white or brown and water soaked in appearance.

"The growing points I observed were 2-6" from the crown and appear healthy an undamaged," said Scheidt.

Stripe rust in boot stage wheat has been confirmed in Montgomery County, KS, which is in the southeast corner of the state. "Scout for light green lesions with bright orange pustules, running in stripes along the leaves," said Scheidt.

According to Greg Luce, state grains specialist with University of Missouri Extension, the first water the corn seed takes in (imbibes) is important for the initiation of germination. A chilling effect occurs when water colder than 50 degrees Fahrenheit is taken in. The cold water disrupts the reorganization of cells during rehydration and can result in the loss of seed vigor or seed death. The most critical time for imbibition is within 24 hours of planting.

"Wait until 2-inch bare soil temperatures will consistently read 50 degrees for a few days before planting corn to avoid injury," said Scheidt.

"Sprouted corn can generally withstand a frost or freezing conditions because the growing point is beneath the soil. Temperatures between 28°F and 32°F are damaging, but can become lethal when they fall below 28 degrees," said Luce.

"The extent of injury to corn and wheat will not be fully evident until temperatures warm and growth resumes. Wait until later this week, when temperatures warm to assess damage," said Scheidt.

For more information about the program, or to sign up for the program, contact Jill Scheidt at the Barton County Extension office, (417) 682-3579.

Photo available for following caption Photo credit: MU Extension

Wheat head after early April frost

Photo available for following caption Photo credit: MU Extension

Sprouted corn after frost

Photo available for following caption Photo credit: MU Extension

Sprouted corn after frost

Source: Jill Scheidt, (417) 682-3579

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