Wheat
Assessing spring freeze damage on wheat
Wheat is often damaged by freezing temperatures during the spring. Wheat's tolerance of freezing temperatures decreases as growth proceeds to flowering in the spring. Wheat is particularly sensitive to sub-freezing temperatures (24-32 degrees F) after the jointing stage. The expected wheat injury sustained at various growth stages is as follows:
Tillering: (Feekes
2-5)
Injurious temperature = 12 F
Symptoms: Leaf chlorosis, leaf burning, blue cast to field, silage odor
Yield effect: slight
Jointing: (Feekes
6-8)
Injurious temperature = 24 F
Symptoms: Death of growing point (head), bending of lower stem at joints,
silage odor
Yield effect: moderate
Boot: (Feekes
9-10)
Injurious temperature = 28 F
Symptoms: Floret sterility, spike trapped in boot
Yield effect: severe
Heading to Flowering: (Feekes
10.1-10.5)
Injurious temperature = 30 F
Symptoms: Floret sterility, white awns or spikes
Yield effect: severe
Milk: (Feekes
11.1)
Injurious temperature = 28 F
Symptoms: White awns or spikes, shrunken, rough, discolored kernels
Yield effect: moderate to severe
Dough: (Feekes
11.2-11.3)
Injurious temperature = 28 F
Symptoms: Shriveled, discolored kernels, poor germination
Yield effect: slight to moderate
