NDSU Crop and Pest Report

Plant Science


ISSUE 4  May 23, 2002

 

WIND INJURY AND HEAT CANKER IN SMALL GRAINS

High winds are in the weather forecast this week. Young tender crop seedlings can be injured by excessive high winds and moving soil particles.

Severe leaf damage can occur in small grains as a result of wind blown soil particles which sand blasts the young seedlings. This type of injury only becomes serious when the growing point or the flag leaf is severely injured. Grain in the three to five stage should recover. Plants in the one to two leaf stage may be more vulnerable because they lack carbohydrate stores to grow new leaves. In most instances with good soil moisture and cool temperatures these plants will recover.

With the potential for warm sunny weather in many portions of North Dakota in the weeks ahead, heat canker maybe observed on small grains. Heat canker is most common on plants less than 4 inches and is favored by dark soils and hot sunny days before plants are large enough to provide shade. Once jointing occurs and stem elongation begins the potential for heat canker is minimal. Heat canker is caused when plant tissues at the soil surface are injured by the hot soil. Typical symptoms are white bands on one or more leaves. These bands appear first at the soil surface but as plant growth occurs they will extend above the soil surface. In more severe cases stems may be constricted at the soil line and the seedlings may fall over. Barley has been observed to be more vulnerable than wheat to heat canker.

In most cases of heat canker on small grains the growing point of the seedling is not injured. Most plants will recover with minimal affect on crop productivity.

Any stress during small grain development will result in reduced productivity. While yield of small grains is determined at harvest, yield potential is determined early in the developmental phases of growth. Yield is determined by the number of heads, number of kernels on a head or head size, and the weight of the kernels. Tillering in small grains typically begins at around the three leaf stage and continues through the five to six leaf stage; varying with environment and variety. Head development is initiated during the four leaf stage. Consequently stress during these early stages, including the two previously discussed, has a negative effect on the final yield of a crop.

 

CANOLA STANDS (HOOP METHOD)

Some canola is emerging while some fields have been reported to have erratic stands. The question comes up, what is an adequate stand in canola? Seeding rates of 5 to 6 pounds per acre should result in 450,000 to 650,000 seeds dropped per acre depending on seed size and numbers per pound. An ideal stand of canola seedlings should be 500,000 plants per acre or 11 to 12 plants per square foot. We donít always reach this ideal goal. What is the "minimum" stand of canola population required to still obtain decent potential yield? Research results from Canada and U.S. have shown that 4 plants per square foot is the minimum stand to still expect good yields. Weed competition however becomes minimal with reduced stands. The canola plant has a way of compensating with additional branching and a thicker stem to support the extra branching when growing under a reduced or lower plant population.

An easy method to determine the stand count in canola is using the "hula hoop" method. Use a hula hoop in a drilled or solid seeded canola field. Randomly toss the hula hoop in 10 different areas of the field and make counts within the hoop.

Using the table below, multiply your average counts by the multiplication factor which corresponds to the size of the hoop being used. The product answer equals the plant population per acre. This method will also work with solid seeded soybean in row spacings of 8 inches or less.

 

Hoop Diameter

Multiplication Factor

30 inches

8,900

32 inches

7,800

34 inches

6,900

36 inches

6,200

38 inches

5,500

Example: 36 canola plants in 32 inch diameter hoop equals: 36 x 7800 = "280,800 plants/A" or 6.5 plants per square foot.

Canola plants per "hoop count" to equal the minimum 4 plants per square foot.

Hoop Diameter

4/ft.2 minimum (canola)
(Number of plants)

30 inches

19.6

32 inches

22.3

34 inches

25.2

36 inches

28.1

38 inches

31.7

After you have counted and determined the canola stand, you can investigate further to see if any additional canola seedlings will or can emerge. Dig or scratch below the soil crust and see if any old or new seedlings have a chance to emerge. Once all the information is assembled then one can judge to leave a field or replant to another crop. Reseeding to canola is getting late and rather risky for this 2002 season.

Duane R. Berglund
Extension Agronomist
dberglun@ndsuext.nodak.edu

 

SUNFLOWER PLANTING DATE MAY AFFECT OLEIC ACID CONTENT

Planting NuSun sunflower varieties too early or late may reduce oleic fatty acid content. Two studies in North Dakota, a date of planting study by the Dickinson and Hettinger Research Extension Centers and Slope County Extension Service (Figure 1) and a study by Miller, Rehder, and Vick of the USDA-ARS Northern Crop Science Laboratory, Fargo (Figure 2) indicate that planting NuSun sunflower varieties early had significantly less oleic fatty acid than plantings made in mid- to late-May. The southwest North Dakota study shows that even plantings made in mid-June had reduced oleic fatty acid content when compared to plantings made in mid- to late-May. The study at Fargo confirms the trend seen in the southwest North Dakota study but that study has a much smaller window of planting dates. The study in southwest North Dakota used a medium-early maturing variety while at Fargo a medium-late maturity variety was used in that study. With processors of NuSun sunflower setting a minimum standard for oleic concentration of 55%, producers will not only need to consider the impact that planting date has on sunflower seed yield but will also need to consider the impact that planting date has on desirable oleic fatty acid content. The April and mid-June plantings in southwest North Dakota produced seed that would be rejected if the minimum oleic fatty acid concentration is 55%. None of the planting dates at Fargo produced seed that contained less than 55% oleic fatty acid.

Both studies can be found on the National Sunflower web site:

http://www.sunflowernsa.com

Summary annual reports for the southwest North Dakota site may be found at the Dickinson Research Extension Center web site:

http://www.ag.ndsu.nodak.edu/dickinso

Figure 1. Combined data of the fatty acid profile comparison of Mycogen 8242 NS for five planting dates, Miles Hanson farm, Bowman, ND, 1999 Ė 2001. (Ashley, Eriksmoen, Whitney, 2001)

Planting dates chart

Planting date: 1st = 26 Apr; 2nd = 9 May; 3rd = 23 May; 4th = 6 Jun; 5th = 17 Jun.

Figure 2. Oleic acid concentration of seed harvested from three different planting dates for Mycogen 8377 NS, Fargo, ND, 2001. (Miller, Rehder, and Vick, 2001).

Oelic acid concentration

Roger Ashley
Area Extension Specialist/Cropping Systems
Dickinson Research Extension Center
rashley@ndsuext.nodak.edu

Dr. Jerry Miller
Research Genetic Plant Scientist/Sunflower
Northern Crop Science Laboratory
millerjf@fargo.ars.usda.gov

 

HARROWING FOR WEED SEEDLINGS

Populations of shallow emerging weed seedlings such as foxtail, kochia, Russian thistle, wild mustard, pigweed, nightshade and below ground white weed sprouts can be severely reduced by timely harrowing. Harrowing will not reduce wild oat, cocklebur and volunteer sunflower populations due to their deeper emergence, and strong root system. However control will be higher if they have not yet emerged and happen to be near the soil surface.

Light spring tooth harrows should be set shallow (1/2 inch deep) and angled back to reduce the potential of crop injury.

Itís best to harrow wheat and barley at the two leaf stage and not later than the three leaf stage to minimize injury potential. Wheat can be harrowed twice while barley should be harrowed only once. Corn can be harrowed between the one and four leaf stage, and sunflower, 2 to 6 leaf stage. Soybean and dry beans can be harrowed between the 1 to 2 trifoliolate stage. Itís advised not to harrow canola, mustard, crambe or flax seedlings. Refer to NDSU Extension Cir. W-1134 for additional information on mechanical weed control with the harrow or rotary hoe.

Duane R. Berglund
Extension Agronomist
dberglun@ndsuext.nodak.edu

 

SOYBEAN PLANTING DATES

Recent university soybean trials conducted in North and South Dakota have included planting date comparisons. During 1999 to 2001, a soybean production trial was conducted at the NDSU Carrington Research Extension Center that included two varieties sown at normal (May 18 to 21) and late (June 1 to 8) planting dates. The normal planting date provided a 6% seed yield advantage versus late planting. However, with early June planting, the short-season variety Daksoy (00.5 relative maturity) maintained yield while Traill (0.0 relative maturity) yield decreased by 5% compared to yield with May planting. A South Dakota State University soybean date of planting trial was conducted at Beresford during 2000-2001 with five planting dates. The first planting date was early May followed by 7- to 10-day planting intervals and ending during the second week of June. Average seed yield with the first 3 planting dates (May 3 to 25) ranged from 46.6 to 48.1 bu/acre compared to 40.4 bu/acre with the early June planting date (June 2 and 4) and 39.2 bu/acre with the last planting date (June 10 and 11). In summary, plant soybean by May 25 for adequate yield potential and select varieties with shorter maturity if planting is delayed.

Greg Endres
Area Extension Crops Specialist
NDSU Carrington R/E Center
gendres@ndsuext.nodak.edu


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