NDSU Crop and Pest Report

Plant Science

ISSUE 16  August 21, 2003


Crop water use, also called evapo-transpiration or ET, is an estimate of the amount of water transpired by the plants and the amount of evaporation from the soil surface around the plants. A plant's water use changes with a predictable pattern from germination to maturity. All agronomic crops have a similar water use pattern. However, crop water use can change from growing season to growing season due to changes in climatic variables (high temperature, amount of sunlight, humidity, wind) and soil differences between fields (root depth, soil water holding capacities, texture, structure, etc.).

Many years of research have produced a number of equations that allow accurate estimates of crop water use values to be calculated from measured daily weather variables. Accurate estimates of crop water use values can be calculated for crops in North Dakota.

Approximate acreage yield, water use and water use efficiency of some crops commonly grown in the northern Great Plains.





Grain Corn
Sugarbeets (Sugar)
Spr. Wheat

5 tons
120 bu
400 cwt
3.2 tons
35 bu
40 bu
1500 lb.


0.2 ton
6 bu.
20 cwt
0.2 ton
2.2 bu.
2.7 bu.
110 lb.

Pinto Beans

25 bu.
2200 lb.
55 bu


1.7 bu.
180 bu.
5 bu.

Source: J. W. Bauder and M. J. Ennen, NDSU Soil Science Dept.

The water use figures in the above table help explain many Agronomists statements, that sunflower is relatively drought-resistant. Several studies have shown that in addition to the low water requirement, sunflower is relatively resistant to the effects of short water stress periods. The water use efficiency (translated as seed production per inch of water use by the plant when water is limiting) represents the response of adequately fertilized crops.



Flax acreage continued to increase in North Dakota in 2003 with 540,000 acres expected to be harvested. A number of new producers have called requesting the proper time to cut and harvest flax.

Flax is harvest ripe when 90 percent or more of the bolls have turned brown and can be combined direct. Any green bolls remaining will crush and pass right through the combine. Direct combining is the cheaper method and is entirely satisfactory when the flax is thoroughly dry and free of weeds. However, the most common method of harvest is with the swather and windrow pickup attachment on a combine because few fields are free of weeds and few ripen uniformly. Flax is considered to be fully mature when 75% of the bolls have turned brown. After this stage has been reached, the crop may be swathed. If regrowth occurs in the fall, cut the crop when the greatest amount of ripe seed can be obtained. Do not delay the harvest too long because fall rains may cause weathering of the mature seed and frost may cause immature seed to turn black, resulting in a reduction in grade. Swathed flax is in condition to combine after a few days of dry weather. Swath rollers are often used to pack the windrow to prevent destruction or movement by wind. When swathing, leave a stubble height of about 4 to 6 inches to hold the flax swath off the ground for good air movement and drying.

Considerable frost damage occurs in immature seeds when temperatures drop to the 27 to 23F range, while leaves are severely damaged at 25 to 23F and stems at 21 to 19F. Cutting or desiccating flax at an immature stage is not known to result in seed blackening, but yields will be reduced due to early termination of seed development. This will result in thin seeds of lower test weight.

Chemical desiccation may be used to accelerate drying of the crop and any weeds that may be present. It does not speed crop maturity, but will reduce the time from maturity to harvest. Potential advantages from this practice are:

  • earlier harvesting;
  • elimination of the need for swathing ( no wind scattered swaths).
  • direct cut harvesting is less risky
  • reduction in combining time;
  • less wear and tear on machinery
  • cleaner seed harvested
  • reduction or elimination of the need for artificial drying
  • A desiccant may be applied after 75% of the bolls have turned brown, which is the normal time of swathing.

    In North Dakota, Drexel Defol (sodium chlorate) and glyphosate can both be used for weed desiccation. Glyphosate should not be used on flax grown for seed purposes since reduced germination/vigor may occur. See labels for correct time to spray desiccants.

    Studies at Morden, Manitoba by Ag Canada researchers, have shown that yields are reduced if applications are made too early. For instance, swathing or desiccating at the 25 to 50% brown boll stages, reduced yields by an average of about 10% and 5% respectively, due to premature termination of development of some of the seed.

    Desiccated flax should be harvested as soon as possible after it is ready, to avoid boll loss and weathering of the seed.

    Flax should be stored at 10 percent moisture or less for safe storage. For long-term storage 8 percent moisture is suggested.

    Duane R. Berglund
    NDSU Extension Agronomist



    This past week I got a call from one of the county agents asking about Holstein oats. Initially I thought he was asking about a variety of oats (one that milk producers would like to feed to their cows?!). I soon found that Holstein oats refers to a poorly understood disease or disorder of oats.

    What is Holstein oats

    Holstein oats is the name given to a disease or disorder that causes black streaks or spots to occur on the oat kernel. The black spotting or stripping on the white colored kernel gives rise to the name of Holstein oats. It has also been referred to as Zebra oats. Since the discoloration can only be seen after the kernel has been de-hulled, most growers with this problem will not learn about it until it is delivered to the elevator. Holstein oats is only a problem of oats intended for the premium market for human consumption as there are no other known deleterious effects associated with the discoloration. I do not know how widespread Holstein oats is in North Dakota; my sense is that it has been noted only rarely. In Saskatchewan, however, it was fairly common last year and there were some reports of it in Manitoba.

    The cause of Holstein oats is currently not known. Water, frost, heat and pathogens or their combination have been proposed as causal agents but nothing conclusive has yet been reported. Since Holstein oats has not been a problem in North Dakota in the past, there has not been any research on it carried out by NDSU. Furthermore, since its cause is not know, there are currently no recommendations on how to prevent it. The intent of this note is to provide some basic background information on a potential problem of oats. I would like to hear from you if you do encounter this problem in your oats this year.



    With the hot and dry weather of the past couple of weeks corn is starting to be stressed. Corn is transpiring nearly ¼ inch of water a day. From the first of August through today (August 18) an early planted corn field in the Fargo area of the state used 4 inches of water. That coupled with the fact that there has been little or no rainfall during this period means that many corn fields are starting to run out of water. The effect of drought on corn growth and yield varies considerably depending on its timing and severity. Corn is most sensitive to drought during flowering, most specifically -1 to 22 days after silking. It is more sensitive at this stage than most crops because the male and female flowers are separated by a considerable distance and pollen and silks are sensitive to hot and dry conditions. When corn is severely stressed prior to flowering, silk growth is delayed and pollen shed will occur before the silks have emerged resulting in barrenness. The corn plant has the capacity to store considerable reserves in the stem, but the developing ear cannot draw upon these reserves until about three weeks after pollination when the kernels are of sufficient size to be an effective sink. Corn that was planted late or that was planted in the drier areas of the state this year was or will be stressed during the critical flowering period and will likely have very low yield potential even if the rains return in the next few days.

    Fortunately, most of the early planted corn crop in North Dakota flowered before the current dry conditions, at least in the eastern half of the state. What can you expect for yield in these fields? Even under the most severe drought situation, if the drought stress occurs three weeks or more after silking, plants will yield at least 30% of what they would have produced if not stressed (Bolaños and Edmeades, 1996). On the more positive side, fields that have not yet shown any outward symptoms of drought stress will probably have limited yield losses if rains return soon. Most early planted (around 1 May) corn crops will probably be somewhere between these two extremes this year.

    How is yield affected by late season drought stress?

    During the first stage of stress, the upper leaves curl or roll towards the midrib during the hottest part of the day. If stress continues, premature leaf death begins at the bottom of the plant and proceeds upward. Leaf death is the first sign of permanent damage to the plant. With severe stress, the upper leaves roll so tightly that they appear like "onion leaves". With less leaf area capable of photosynthesis, grain filling is slowed even while maturing at an accelerated pace. Carbohydrates that had been stored in the stem earlier in the season are moved to the developing ear. Not surprisingly, drought stressed crops are more prone to lodging because of poor stalk health. There may be some kernel abortion in the tips of the ears, but for the most part, kernel numbers are not reduced significantly with late season drought. Yield losses will largely be due to reduced kernel size and reduced test weight. The amount of reduction will be related to the amount of stress prior to harvest.

    Premature leaf death and upper
    leaf rolling in corn as a result of drought stress.

    Drought-stricken Corn for Fodder?

    For a severely stressed corn crop it might be time to consider using it for fodder rather than for grain. If you expect yields of less than 40 bushels per acre it may be hard to justify the cost of harvesting the crop for grain. Corn can be grazed while still green, taken as a green chop or left for late fall grazing. The fodder quality of corn plants declines rapidly the longer it stands in the field, so now is the right time to make a decision on whether to use your crop as a fodder and if so, how. Stressed green corn stalks can accumulate nitrates and can potentially be toxic to cattle.

    You can obtain additional information on how avoid nitrate toxicity in stressed corn used as fodder by contacting Greg Lardy, Extension Beef Cattle Specialist (701-231-7660, glardy@ndsuext.nodak.edu ).

    Joel Ransom
    NDSU Extension Agronomist - Cereal Crops



    Successful winter wheat producers in southwest North Dakota commonly seed into standing spring wheat stubble for protection against temperature extremes which often occur during winter and early spring. In addition to the stress on plants produced by these extreme conditions soil-borne pathogens may affect the ability of winter wheat to survive the dormant period into the following spring. "Winter Kill" or combination of weather extremes and soil-borne pathogens results in thin stands making winter wheat less competitive and more difficult to manage in terms of weed control and harvest management. A number of protectant or systemic seed treatments are registered for seed treatment. Some are specific for certain seed or soil-borne fungi; others are wider spectrum. Often several products are used in combination or are formulated to provide control of a wider spectrum of diseases.

    Following are the results of various registered seed treatments conducted in the Dickinson area for 2003. Protein values were not available at this time. Experimental treatments are not shown in these tables.

    Winter wheat (cv. Falcon) seed treatment on the Ryan Kadrmas Farm, Dickinson, ND, 2003.




    Head density



    Test Weight




















    Dividend XL 1.67 FS






    Raxil XT






    Raxil XT + Gaucho 4802


















    LSD .05












    1 All grain yields, test weights, and proteins are adjusted to a 12% moisture basis.
    2 Guacho 480 and Crusier FS are insecticides.

    Stand counts for Falcon hard red winter wheat with various seed treatment, Ryan Kadrmas Farm, Dickinson, ND 2003.


    10 April 2003





    Fumigated Soil


    Raxil XT


    Raxil XT + Gaucho


    Dividend XL






    LSD .05


    Check = untreated seed.
    Fumigated = fumigated soil treatment.
    Dividend XL 1.67FS = Dividend XL 1.67FS @9.75 grams/100Kg seed.
    Raxil XT = Raxil XT 35WP @ 3.5 grams/100Kg seed.
    Raxil XT + Gaucho 480 = Raxil XT 35WP + Gaucho 480 @ 3.5 + 5.0 grams/100 Kg seed.

    Additional information on seed treatments is available in the 2003 North Dakota Field Crop Fungicide Guide from your county extension agent.

    Wheat streak mosaic virus can be a problem in southwest North Dakota. Seed treatments are not available to control this disease. This disease can be minimized by seeding in the recommended planting window for the southern half of North Dakota, September 10-30. Planting earlier than these dates increases the likelihood of infection by wheat streak mosaic virus – a disease transmitted by wheat curl mites. In areas where this disease is prevalent seeding should be delayed until the later part of the recommended planting window.

    Roger Ashley
    Area Extension Agronomist
    Dickinson Research Extension Center

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