Diagnose wheat affected by freezing temps

Freezing temperatures can affect wheat fields within the Colorado High Plains region some seasons. In fields where only some of the tillers have been damaged, there is still plenty of time for undamaged tillers to compensate and minimize any potential yield loss. However, frost damaged wheat heads will be permanently damaged. Wheat heads emerging white in color indicate frost damage and will not produce seeds.

Determine freeze damage
There are a number of key factors in determining freeze damage: the stage of development of the wheat, the density of the stand and condition of the plants, the amount of residue on the soil surface, the extent and duration of low temperatures, temperature gradients within the field, soil moisture and the wind speed.

—Stage of development: Wheat that has greened up but hasn’t started to joint yet will probably suffer damage to the existing foliage, but the growing points will be protected by the soil and should escape injury. This wheat will have cosmetic damage to the leaves that will show up almost immediately. If new leaves emerging over the next few weeks are green, that will indicate that the growing points survived and the plants will still produce tillers. If the new leaves are yellow, the growing point of that particular tiller was killed by the freeze.

Jointing wheat can usually tolerate temperatures in the mid to upper 20s with no significant injury. But, if temperatures fall into the low 20s or even lower for several hours, the lower stems, leaves or developing head can sustain injury. If the leaves of tillers are yellowish when they emerge from the whorl, this indicates those tillers have been damaged. Existing leaves may also be damaged so severely that they turn bluish-black and have a water-soaked appearance, then bleach out. This usually results in the field’s having a “silage smell.”

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