Cold damage to cereals
Below is a response from Cereals Extension Specialist Russ Karow and comments from others to a question regarding the cold weather in late December, 1998 and potential damage to cereals crops.
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Question: Do you have any concerns about the cold weather and the 1999 wheat crop?
Russ Karow's Answer: Yes, the cold is of concern. This will be the first real test we've had of Gene in many years. I would guess that Gene will get toasted back to the ground. Other varieties are also susceptible in that we had fairly warm temperatures going into this cold spell which means plants were not well hardened. The wind is generally more problematic than the cold per se as the combination tends to freeze-dry plants. This effect is intensified when plants are in water-stress situations. Plant size goes both ways as to whether it's good or bad. Small plants get less wind exposure and tend to have a higher solute level in their tissues and hence are less prone to injury under some cold conditions. On the other hand, if it freezes hard, the leaves and tillers of larger plants tend to act as insulating layers and also rupture first releasing water and solutes which in turn freeze and actually create a ice ball cocoon of sorts around the remaining tissues which may keep these tissues somewhat warmer. Little plants don't have this protection available to them. If it gets real cold, they just freeze. Large plants are more prone to freeze-drying as they have greater tissue exposure. I would expect that every field will show different end results depending on plant size, variety, moisture status, etc. The other thing we've seen in the past is that plants have survived the cold and are then wiped out later in the season by cephalosporium stripe due to the extensive tissue injury caused by the cold.
Overseeding is an option if there is injury and you don't think there will be a cephalosporium stripe problem. Overseeding with a spring grain makes more sense than using a winter. If there has been any evidence of cephalosporim problems in a field in the past or it has a long history of Stephens production, I would recommend some serious penciling on reseeding per se.
County agents - could you folks send the group your thoughts on the situation in your area when you get a chance. If you have time, could you all also pull some plants after the cold front passes and do a rag doll test as described in the attached article if you have injured fields in your area and let us all know the results. Thanks!
How many ways to kill a wheat plant, let me count the ways ...
Cold Damage to Cereals (written following the December 1991 cold weather)
By Russ Karow
First indications are that the late December (1991) cold snap was not as damaging as it could have been, but you are still likely to get many questions regarding injury assessment and replanting considerations. Below are my thoughts on these and related topics (in part an excerpt from a similar 1984 note).
Cold injury is influenced by several factors: 1) the physiological condition of the plants when the cold snap occurs; 2) genetic differences in cultivar hardiness; and 3) snow cover and moisture conditions during the cold period.
The worst case scenario for cereals is to move from a period of warm temperatures (40+F) and active growth to cold temperatures (<10F). Under such conditions the plants do not have an opportunity to "harden" (to shut down physiological functions). Hardening involves production of special gums and resins which resist frost damage, lowering of the moisture content of the crown etc. Without a hardening period, even the most winter hardy cultivars can sustain injury. With a gradual de-cline in temperature, winter hardy cereals are able to survive temperatures below 0F for short periods of time even without snow cover.
In addition to rapid drop in temperature, freeze and thaw cycles are also detrimental to the hardening process. Level of winter hardiness can decrease if temperatures fluctuate widely. Duration of sublethal temperatures is also a factor. Canadian re-search has shown that at 5F the ability of plants to survive declines after 12 hours of exposure. At 0F survival rates drop after only one hour.
There are significant differences in the genetic winterhardiness of cultivars. Stephens, Yamhill, Malcolm, Oveson, and Whit-man have low levels of hardiness while cultivars such as Daws, Cashup, John, Nugaines, Hatton and Wanser are quite hardy. Refer to current cultivar publications for hardiness ratings.
Snow cover and soil moisture play significant roles in cold in-jury. Experience indicates that even a light snow cover, especially in deep furrow plantings, can prevent serious damage. In the Midwest, hardened wheats with snow cover have survived air temperatures of -40 to -45F degrees. Cold injury is also in part a dehydration process. Water freezes in intercellular spaces which leads to water loss from cells and water movement in the plant. If a plant is under water stress, injury may occur due to desiccation - freeze drying essentially. But high moisture content can also lead to injury. High water content in the crown can lead to dilution of natural antifreeze materials and thus make these materials less effective.
Injury in cereals progresses from older to younger tissues. The crown and meristems (growing points) are most hardy. 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.
One useful method of checking for plant viability is the "rag doll" or paper towel test. (See also comments from Mike Stoltz)
1. First, collect a representative sample of plants from the field. Collect plants from both good and poor areas. Collect whole plants by digging with a shovel or pick. Try to minimize crown damage in the digging process.
2. Carefully wash the plants removing dead tissue and soil. Try not to damage the crown or tillers. If large root masses are present, these may be cut off several inches below the crown. Likewise, leaves may be cut off several inches above the crown; however, if there is several inches of green healthy growth above the crown it is probably not necessary to run this test. The plant is likely to be alive.
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 alternatively, place the moistened towels into a plastic bag. The plants must not dry out.
4. Place the plants in the refrigerator or other cool place overnight to acclimatize them to the warmer indoor temperatures, then move to a warm location (60-65F). If the plants are alive, new growth should appear on the main stem or tillers within several days.
Even if the plants are alive, there are other concerns. In the 1989 freeze, fields survived but were later devastated by Cephalosporium stripe. Root breakage which accompanies freeze events is one of the factors which leads to the occurrence of this disease. If Cephalosporium has been an on-going problem in a field, reseeding may be beneficial.
If plants have survived a grower must also decide whether the remaining stand is adequate to meet yield expectations. Paper gymnastics of the following type could be used to estimate maximum yield potential.
Two surviving plants per linear foot of 10" row would equate to 2.4 plants per sq ft (2 plts/ .833 sq ft) or 104586 plants per acre (43560 x 2.4). If each surviving plant produced four heads and each head produced an average of 48 seeds (16 spikelets with three seeds each) and each seed weighed 45 mg (@10,000 seeds per pound) then yield would be 2008 lb/a or 33.5 bu/a [(104586 x 4 x 48) / 10,000].
Tillering rates of 3-8 tillers per plant are possible, 4-5 most likely. Stephens head size ranges from 12 to over 20 spikelets per head (average 16-18) with three kernels per spikelet. An average seed size is 10,000 seeds per pound.
As for reseeding, Stephens is the only winter wheat that should be considered for planting at this time. It has been successfully planted into the middle of February and even as late as early March in some years. Malcolm is likely to behave similarly, but experience is limited. Other cultivars such as Daws, Hill81 and Nugaines have a long vernalization requirement and there would be risk involved in planting beyond early January. (How late can I plant winter wheat? Using weather data to predict vernalization.)
I hope these ramblings are of use to you. The bottom line is to try to assess level of damage and then consider the options from an economic standpoint - overseeding, reseeding, etc. Each situation is likely to be unique and each solution will carry a different economic burden and risk. There are no easy answers.
A related comment from Chris Mundt, Plant Pathologist:
Just a quick addition to Russ's message. I've seen Gene frozen back to the ground as many as three times in a season and still come through in Pendleton. It seems that the nail in the coffin often is the herbicide program. Cold plus Karmex or Fargo has taken out my Gene plots on multiple occassions in the Willamette Valley, and I've heard stories of the same interactions with metribuzin on the east side. This is probably another important variable to put in the equation.
Mike Stoltz on the "rag doll" test:
I will add my two bits in here: I tried the rag doll test one year where we had a lot of damage in Pendleton. I found that the some of the plants would grow but then died after about 1 week - 10 days. Sure enough, those spots in the field where those plants came from also died the next spring. So there was a lot more damage than I thought based on the rag doll test after about 4-5 days.
I found another method that is better. Clarence Peterson, retired wheat breeder in Washington, showed this method with slides.
Here is the method: When the field unthaws enought to dig plants walk through the field and dig plants at random, at least 100. Take them in and wash them off. Take a real sharp knife and slice the plant through the crown lengthwise. Those plants that are OK will be white with yellow center. Those that are damaged will have a brown center. It really works well on 2-4 leaf wheat.
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Cold damage (brown center) ----------- Healthy (yellow center)
A fieldman and I tried this method '93 on 10 different fields. Our percentages turned out to be right on the money when spring rolled around.
I think it would make a great bulletin, especially if one could get Clarence's slides or I guess someone could take new slides. Try it out and compare it to the rag doll test. Leave the rag doll test 2 weeks.
Last updated Dec. 21, 1998.
Crop & Soil Science WWW, Oregon State University
(http://www.css.orst.edu/cereals/)