Cold weather threatens crops, according to MU Extension agronomy specialist in Lamar

Jill Scheidt, agronomy specialist with MU Extension, scouted fields April 4. She found earlier planted wheat jointing, while later planted wheat was still tillering.

"Cold weather could affect crop growth," said Scheidt.

If wheat is tillering, slight to moderate damage can occur if temperatures are at or lower than 12 degrees Fahrenheit for two or more hours. Symptoms include leaf chlorosis, burnt leaf tips, silage odor and blue cast to fields.

If wheat is jointing, moderate to severe damage can occur at temperatures at or lower than 24 degrees for two or more hours. Symptoms include the death of the 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.

According to Purdue University, if temperatures drop below 28 degrees for a few hours, the growing point of young corn plants can be injured or killed even if it is still below the soil surface. Leaves may blacken and wither. Yield loss due to early freeze is primarily related to stand loss.

Newly planted corn may be at risk if soil temperatures drop to 50 degrees or lower within 24 hours of planting. If the seed absorbs cold water, the cold water disrupts the reorganization of cells and can result in loss of vigor or seed death.

According to Kaitlyn Bissonnette, pathologist with MU, prolonged cold, wet weather after a freeze increases the chance for disease development of corn. Soil type and management of the soil, for example, tilled or not, can affect extent of damage too.

"The extent of injury to corn and wheat will not be fully evident until temperatures warm and growth resumes. It is best to wait at least one week or until temperatures warm to assess damage," said Scheidt.

According to the MU Lamar Weather Station, the 2-inch bare soil temperature was 35 degrees Fahrenheit at 8:30 am on April 4.

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.