Winter Wheat Condition Updates

Winter Wheat Condition Updates

May 16, 2008

Graph showing how a freeze affects different growth stages of winter wheat.
Figure 1. How freezing temperatures injure wheat at various growth stages. Winter wheat rapidly loses hardiness during spring growth and is easily injured by late freezes. (Graph adapted from A.W. Pauli for UNL Extension EC132, Freeze Injury to Nebraska Wheat.)

Robert Klein, Extension Cropping Systems Specialist at the West Central REC, North Platte: Winter wheat in west central Nebraska is about 10 days behind normal development, which probably saved the crop when low temperatures occurred May 11.

On May 10 and May 11, 1981 similar temperatures occurred near McCook. Winter wheat at the normal development stage had just headed and growers experienced major losses. Decatur County, Kansas, which adjoins Red Willow County (McCook) also had major losses in 1981 to its winter wheat crop. Those counties each had the highest winter wheat losses from the freeze for each of their states.

Also see this week . .
Wheat Disease Update
Wheat Fungicides Update

The late stage of development is a plus for protecting the crop from freeze injury (see Figure 1 and Table 1, below), but means that the crop will be filling later, probably under higher temperatures. Temperatures above 85°F during the filling period shorten the filling period and reduce yields, even if sufficient water and nutrients are available.

Later development also allows more time for disease and insects to build to economic levels. Producers and crop consultants will need to scout fields regularly and treat where economical.

Douglas Anderson, Extension Educator in Keith, Arthur, and Perkins counties: Wheat is at early jointing. The weather stunted back growth and leaf tips were frosted. It will start growing in earnest with sunshine.

William Booker, Extension Educator in Box Butte County: I haven't seen any early frost damage. In 2005 we had 11 degrees here on May 8 and it was early enough to not hurt the wheat. Many things impact wheat yield — cold weather near pollination would be a killer.

Karen DeBoer, Extension Educator in Cheyenne County: The wheat in our area is jointing and recovering from the cold winds we had with the blizzard on May 2. It still shows signs of wind damage, but I have not seen any diseases developing. I expect it will recover, especially with the warmer temperatures that are forecast.

Drew Lyon, Extension Dryland Cropping Systems Specialist, Panhandle REC, Scottsbluff: The wheat here didn't sustain serious injury from the freezing temperatures. Much of it recently jointed and the jointed plants formed a good canopy, which helped protect the growing point. Freezing temperatures in the future will be more likely to cause significant damage.

Table 1. Temperatures that cause injury to wheat at spring growth stages and symptoms and yield effect of spring freeze injury.
Growth stage Approximate injurious
temperature

(two hours)
Primary symptoms Yield effect

Tillering 12 F Leaf chlorosis; burning of leaf tips;
silage odor; blue cast to fields
Slight to moderate
Jointing 24 F Death of growing point; leaf yellowing or burning;
lesions, splitting, or bending of lower stem; odor
Moderate to severe
Boot 28 F Floret sterility; head trapped in boot; damage to
lower stem; leaf discoloration; odor
Moderate to severe
Heading 30 F Floret sterility; white awns or white heads;
damage to lower stem; leaf discoloration
Severe
Flowering 30 F Floret sterility; white awns or white heads;
damage to lower stem; leaf discoloration
Severe
Milk 28 F White awns or white heads; damage to lower stems; leaf
discoloration; shrunken, roughened, or discolored kernels
Moderate to severe
Dough 28 F Shriveled, discolored kernels; poor germination Slight to moderate