Cold Temperatures Raise Concerns about Winter Kill in Wheat Fields
Mary K. Corp, and Larry Lutcher, OSU Extension Agronomists, Umatilla and Morrow Counties.
Unseasonably cold temperatures last week raise the issue of potential cold damage to
cereal crops in the minds of local wheat growers. The effects of the recent cold
temperatures on the winter wheat crop will show up as black or a dark-shade of purple on
wimpy leaves. Local conditions may well have set the crop up for some level of injury
but only time can reveal the full extent of the impact.
The amount of cold injury is often influenced by several key factors:
 The physiological condition of the plants when the cold snap occurred, i.e. under
water stress is one factor,
 The rapid movement from warm temperatures (40+F.) and active growth to cold
temperatures (<10F.), and
 Genetic differences in cultivar hardiness.
Most local fields have adequate moisture in the surface foot, so we may have dodged the
water stress bullet. We did ease into the extreme cold over a 10 day period, until we
reached temperatures at 27F below normal. This may have given plants some
opportunity to “harden”. Hardening involves production of special gums and resins,
which resist frost damage, and the lowering of the moisture content of the crown. Still the
lack of snow cover and high winds – can have drastic impacts on exposed areas of our
hilly terrain.
There are significant differences in the genetic winter hardiness of cultivars. Many
growers planted fields to Tubbs-06, Tubbs, Goetze, ORCF-101 or ORCF-102. Others are
raising Stephens, WB-528, Skiles, Gene, or some combination. Tubbs and Tubbs-06 will
tolerate more cold than Goetze or Gene. As few years ago, Larry Lutcher observed winter
injury on ORCF-101, while adjacent fields of Tubbs and Tubbs-06 were unaffected.
Variety
Gene
Goetz
ORCF-101
ORCF-102
Stephens
Tubbs
Tubbs 06
Cold Tolerance
Rating
2
2
4
5
3
5
5
Growing a hard red winter wheat? Finley and Paladin have high cold tolerance ratings of
six(6). Norwest 553 is rated at a four (4) which is still higher than Stephens so under most
conditions it should have adequate tolerance.
Injury in wheat progresses from younger tissue to older tissue. The crowns and growing
points are the most hardy parts. Sugars and other water-soluble materials are in highest
concentration in these tissues and act as antifreeze. Often all above ground leaf tissue will
be dead, but tiller and main stem growing points will survive and regrow.
Growers are encouraged to check their wheat plants for viability using the paper towel
test:
Paper towel test
1. Collect a sample of plants from the field in question. Collect plants from both
good and poor areas. Collect whole plants by digging with a shovel. Try to
minimize crown damage in the digging process.
2. Carefully wash the plants removing dead tissue and soil. Try to not damage the
crown or tillers.
3. Moisten several pieces of paper towel and lay the plants on the towel with green
tissue, if any, extending over the top edge of the towel. Roll the towel into a
cylinder and place the bottom end of the towel in a container partially filled with
water, or place the moistened towels in a plastic bag. The plants must not dry out.
4. Place the plants in the refrigerator or other cool place overnight to acclimate them
to the warmer indoor temperature, and then move to a warm location (60-65F).
If plants are alive, new growth should appear on the main stem or tillers within
one week to ten days).
If plants have survived growers must decide whether the remaining stand is adequate
to meet yield expectations. Paper gymnastics could be used to estimate maximum
yield potential. Russ Karow, former OSU Cereal Specialist, offered the following
exercise for ballpark estimates:
Two surviving plants per linear foot of 10 inch row would equate to 2.4 plants per
sq ft (2 plts/.833sq ft) or 104,586 plants per acre (43,560 x 2.4). If each surviving
plant produces four heads and each head produces an average of 48 seeds and
each seed weighs 45 mg (@10,000 seeds per pound) then yield would be 2,008
lb/a or 33.5 bu/a.
Even if the plants are alive there is the potential for Cephalosporium stripe to become
a problem. In 1989, fields survived a freeze but were later devastated by
Cephalosporium stripe. Root breakage, which accompanies freeze events, is one
factor that increases the occurrence of this disease. If Cephalosporium has been an
on-going problem in a field, reseeding may be beneficial.
The bottom line is to try to assess the level of damage and then consider the options
of reseeding or overseeding from an economic standpoint. Each situation is likely to
be unique and each solution will carry a different economic burden and risk. There
will be no easy answers, but we hope this information helps you plan for whatever
“lies ahead.”