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Wheat producers need
to assess damage now
Nebraska
Wheat growers in west central and southwest Nebraska need to check their fields for freeze damage. Recent low temperatures caught the area's Wheat crop at its most vulnerable stage of development, a University of Nebraska cropping system specialist said.
With temperatures as low as 26 degrees at North Platte and winter Wheat about 10 days ahead of normal development, the freeze probably killed or damaged many Wheat plants' anthers, said Bob Klein, cropping system specialist at the university's West Central Research and Extension Center here.
"This results in sterility because the anthers produce the pollen that is essential to kernel development," Klein said.
The length of time that temperatures stayed below freezing is critical, he said. North Platte was below freezing for 5 hours on May 14. Klein said it's also important to note that temperatures at the wheat's head, near the ground, probably were lower than officially recorded lows. Several factors influence the microclimate at the wheat's head, including density of plant canopy, soil moisture, humidity and wind speed.
"If there was any damage from this frost, it will mostly be to winter wheat," Klein said. "The biggest potential is in west central Nebraska, but southwest Nebraska could have sustained damage as well."
After the weekend's warmer conditions, fields should be ready for growers to survey damage.
"After assessing damage, growers will want to make sure their crop is worth harvesting," Klein said. "The crop is going to have to yield at least 10 bushels per acre for it to be worth harvesting."
It's important for growers to contact their local Farm Service Agency and crop insurance agents before doing anything to their crop, Klein said.
Producers concerned about possible freeze injury should examine the anthers inside each floret from several Wheat heads, Klein said.
The anthers, or male parts, are more vulnerable to low temperatures than are the stigmas or female parts, Klein said. Wheat is self-pollinated so each kernel needs live anthers to develop.
Freeze-damaged anthers become twisted and shriveled within 48 hours after a freeze, then quickly turn white to whitish-brown. If the anthers are still in the floret and dried up, pollination has not taken place. They will be extruded if pollination has taken place.
"A week or so after freezing, look for continued kernel development," Klein said. "Sometimes only a few florets are damaged while at other times the entire head is killed. If you have good kernel development, you probably had little or no freeze damage."
Chlorosis or bleaching of the awns (beards) is the most apparent freeze damage to a Wheat spike that has just headed. This results in a whitish color rather than the normal green color. Low temperatures that damage the awns also may damage the male flower parts.
If the spikes head out normally but remain white or yellow instead of green, damage probably is limited and the crop may be worth saving, Klein said. In some areas, parts of the field may be damaged, while others are not.
If the crop is a total loss, some possibilities include making hay out of the crop.
However, it may be best just to spray the crop with herbicide to kill it so it doesn't use any more moisture, Klein said.
"If you hay the crop, then you won't have any residue left to protect the ground from erosion," Klein said. "That residue is really valuable for the next (year's) crop by protecting the soil, reducing wind velocities, reducing soil temperatures to trap more snow and helping conserve moisture in the soil."
Planting another crop probably isn't wise because of limited soil moisture, Klein said.
Details about assessing damage to Wheat are available in Crop Watch, Nebraska Cooperative Extension's crop production newsletter, on the Web at http://cropwatch.unl.edu/. For more information about freeze injury to wheat, consult Nebraska Cooperative Extension Circular EC 94-132-S, Freeze Injury to Nebraska Wheat, available at a local Extension office or on the Web at http://ianrpubs.unl.edu/fieldcrops/ec132.htm.
Date: 5/19/04
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