April 20, 2007

It appears that most of the winter wheat in western Nebraska did not suffer major freeze injury. Some winter wheat fields in eastern and south central Nebraska appear to have moderate to severe injury to main tillers and also injury to secondary tillers in some areas. This includes stem damage, lodging and damage to the young heads in the stem. How much this wheat recovers depends on how much development there is from secondary and basal tillers. With this week's warmer weather a more accurate assessment of freeze injury can be made.

Evaluating the condition of winter wheat is always difficult. Everyone has heard the old saying, "Winter wheat has nine lives," and many years we use most of them.

Last fall many fields were seeded late because of wet conditions and a delay in when soybeans dried down for harvest. We also had ice on many winter wheat fields this winter. Now with the freeze injury, we can see that we're using a number of those nine lives.

A major factor in winter wheat yields is the length of the filling period. The longer the filling period, the better the yields. Temperatures above 85°F shorten the filling period and decrease yields.

We might estimate a field has 25% freeze injury, but if we have a long cool filling period, we still could have some of our best winter wheat yields. Likewise if we again estimate that the field has 25% freeze injury and the filling period is short with hot weather, yields may be even less than 50% of normal. Freeze injury does delay the onset of winter wheat filling so injured winter wheat yields can be reduced if the weather is hot at the filling stage. Early freeze injury is difficult to evaluate unless it kills the plant. Therefore, growers should be cautious about estimating yield loss as a result of the freezing conditions in early April. Winter wheat is a crop well adapted to the vicissitudes of Nebraska weather and should not be counted out prematurely.

Bob Klein
Extension Crops Specialist
West Central REC, North Platte
Paul Hay
Extension Educator, Gage County
Drew Lyon
Extension Dryland Crops Specialist
Panhandle REC, Scottsbluff