Beware Of Cold Injury To Wheat Says MU Extension Agronomy Specialist

LAMAR, MO.
   Low temperatures can kill winter wheat plants by injuring the crown according to Jill Scheidt, agronomy specialist with University of Missouri Extension.
   “When adequately hardened, crowns can tolerate temperatures of -9 to -11 degrees Fahrenheit,” said Scheidt. “Plants in the 3-4 leaf stage with good root systems are in the best position to survive the winter.”
   The planting date is important not only when considering protection against Hessian flies, but also to protect plants from cold temperatures and unpredictable weather that occurs in Missouri.
   “If plants put out too many tillers in the fall, the overly lush plant will be more susceptible to cold temperatures. Larger plants are more subject than younger, smaller plants to shriveling due to cold, dry winds and lack of adequate snow cover,” said Scheidt.
   Wheat should not be planted before Oct. 10 south of Vernon County to Jasper County and ranging east to the state line; and not planted before Oct. 14 south and east of Newton County to Missouri's state borders to avoid yield loss caused by Hessian fly and cold temperatures.
   “Plants that are killed by low temperatures will normally fail to green-up in the spring and have a bleached-tan color to the leaves. These symptoms will be most apparent on exposed high areas of the field. The crown tissue of winter injury plants will be soft, brown and mushy and secondary roots will have rotted off,” said Scheidt.
   Healthy plants have firm, pale green crowns and white roots. Severity of freeze injury to wheat depends on temperature, length of exposure and growth stage.
   Plants can be checked for winter injury by digging them up before spring green-up and bringing the plant indoors. If the crown tissue is still alive, new growth should be visible within three days on plants clipped at one-half to three-fourths inches above the crown.
   According to Scheidt, wheat has the maximum amount of resistance to cold temperatures during mid-December to the end of January. Wheat can withstand temperatures of -9 to -11 degree Fahrenheit. Wheat can withstand temperatures as low as -5 degree Fahrenheit until the end of February.
   “If there is 4 inches of snow to cover wheat plants during cold temperatures, the snow will provide enough insulation to protect the plant. If there is less than 4 inches of snow covering plants during temperatures of -4 degrees Fahrenheit or below, producers should check their fields for freeze injury,” said Scheidt.
   The tillering stage usually occurs in the fall when the plant has 4 to 5 leaves. During spring tillering, beginning in March, if temperatures drop to 12 degrees for more than 2 hours, a wheat plant may see a slight to moderate yield reduction. Symptoms include leaf chlorosis, burning leaf tips; you may also see a blue cast to the field.∆