Written by Rickey Roberts Tuesday, 10 April 2007 22:09Overnight temperatures dropped into the critical zone for several evenings in a row this past week. Normally, a hard freeze in early April is not a problem for wheat. But this year, the crop is about two weeks ahead of normal development.
Producers should not make any quick decisions about the condition of their wheat crop after the freezes. It will take several days of warm weather following the freezes to evaluate the condition of the crop.
Even if some of the main tillers are injured or killed, producers should wait to see if enough other tillers have survived to compensate for the lost yield potential.
As of today, that would be my guess.
Patience is the key at this point in the season. Three factors are important in determining whether there will be any damage to the crop from the freezes this week: stage of wheat development, temperatures, and wind speed.
The temperature ranges mentioned below are not hard and fast rules, but general guidelines. Whether actual freeze injury takes place depends on: (1) the lowest temperature reached, (2) the effect of the unusual snow cover we had, (3) how long the temperatures stayed that cold, (4) wind speed, (5) canopy density, and (6) other microclimate factors.
Soil moisture is another factor that is usually important in determining freeze injury, but this year moisture levels are good.
In the jointing stage, wheat can usually tolerate temperatures in the mid to upper 20s with no significant injury. If temperatures get into the low-20s or lower for several hours, injury can occur to the lower stems, the leaves, or the developing head.
If it is windy during the nighttime hours when temperatures reach their lows, this increases the chance of injury.
Normally, soils that are warm and moist will be radiating heat into the canopy. This helps protect wheat from freeze injury unless conditions are windy.
With the snow fall it is possible that the ground was chilled to prevent this from happening.
When and how will producers know if their wheat in the jointing stage has been injured by cold temperatures?
After temperatures warm up, damage may be apparent within seven to 10 days. If temperatures stay cool for another week or two, it will take longer to notice any freeze injury.
Injury symptoms will vary. If the main tillers are injured, secondary tillers which were buried under the snow will begin growing normally and fill out the stand.
The wheat may have a ragged appearance because the main tillers are absent, but there may still be enough surviving tillers to produce good yields if spring growing conditions are good.
If we are going to lose our main tillers, early April is not a bad time for it to happen as there is plenty of time for secondary tillers to develop.
If the lower stems are damaged by freeze injury, the wheat plants will likely lodge at some point.
Lodging could also be caused by other factors, however, so it will be important for producers to examine the lower stems on lodged plants to determine the cause. Plant may have simply leaned over due to snow and will eventually come back up if the lower stem isn’t damaged.
In summary, the wheat I have seen appears to have stem damage. Thus as we sometimes have “market corrections” we may have a “tiller correction.”
Actual damage, if any, will not become apparent until temperatures have warmed back up for several days and growth has resumed. Even then, you’ll not find me giving “last rites.” I can still remember 1997.
For more information on freeze damage to wheat, see “Spring Freeze Injury to Kansas Wheat,” K-State Research and Extension publication C646.
On the alfalfa crop, it appears the growing point has been killed, causing the terminals to turn down like a shepherd's crook.
If so, the first cutting is pretty much done. I’d try to mow off the top growth, which should allow the regrowth to come back more quickly.
Please remember that weevils are cold-weather creatures, so they have bailed to the base of the plant or even below ground. But they will be hungry once it warms up so keep a close eye on the regrowth, even if you have already sprayed.