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ISSUE 6  JUNE 10, 1999

 

SUNFLOWER - HOW LATE CAN WE PLANT?

    Most years in North Dakota, a number of sunflower fields are planted late or replanted. The many
reasons for this include: extremely cold or wet conditions, wind erosion, insects (cutworm), diseases,
hail and frost. This wet year, 1999 will go down as one of the later planting of sunflower and many other crops.

    Research on late planted sunflower has been conducted at various North Dakota NDSU Research
Center sites. Results of these studies are shown below:

Table 1. Sunflower yields* (lb/A) as influenced by
planting dates at Prosper and Carrington, ND

Approximate planting date

Hybrid

% oil

SW101**

894

June 1

2046

2087

43.9

June 15

2323

1891

44.1

June 30

1692

1076

40.5

July 15

312

123

33.9

* Average 3 years, 2 locations

** Sunwheat 101 - early semi-dwarf sunflower

 

Table 2. Sunflower oilseed yields*- Early vs. late planting

Planting time

 

Langdon

 

Minot

Mid May

1828

1632

Early June

1179

1368

 

diff.

649

diff.

264

* 5 year ave. Yields - lbs/A

    When planting sunflower late (after June 5) it’s suggested to plant early maturing hybrids. Selection of
short season sunflowers will increase the chance of reaching maturity in the northern areas of North Dakota
and Minnesota. Planting of non-oilseed or confectionary sunflowers is discouraged in June.

 

FLAX SEEDING - HOW LATE?

    Flax is an alternative oilseed crop that can be late planted with reduced yield potential. How late is the
question many ask in North Dakota this year. Below are data from studies at the NDSU North Central
Research and Extension Center at Minot, ND.

    Flax seeded the middle of June, late June and early July, periods 4, 5, and 6 yielded 32, 52 and 84
percent less than flax seeded in early May, period 1, see table following. This would indicate that
seeding flax prior to the middle of May is important in obtaining 20 plus bushel flax yields.

 

Flax seeding date studies, Minot

Seeding periods

Yields* (bu/A)

1st (Early May)

23.5

2nd (Mid-May)

21.8

3rd (Late May)

18.5

4th (Early June)

16.0

5th ( Mid-June)

11.3

6th (Early July)

3.8

Nine years (1977-1985)
*Yields averaged over 10 varieties

    Mid June planting of "early" varieties yielded 79 percent of their early May planting while late
maturing varieties planted in mid June yielded 42 percent of their early May planting. Please note:
NorLin was the highest yielding early variety when seeded the middle of June - period 4. These
data support the recommendation to plant early maturing varieties when seeding in June.

In summary this nine-year study of planting date of flax indicates that delayed flax planting will
reduce yield potential. Flax planted in periods 2 through 6 yielded 93, 79, 68, 48 and 16 percent,
respectively, of flax planted in period 1 when averaged over all varieties.

 

PLANT BUCKWHEAT NOW

    Buckwheat is planted later than small grain, corn, beans and sunflower. It is very sensitive to spring
and fall frosts and any seeding should be delayed until all danger of frost is past. Best planting dates are
from May 25 to June 10 in most years. Research date of planting studies at Langdon during 3
years indicated significant buckwheat yield reductions when seeding was delayed to June 22 or later.

    It requires about 10-12 weeks after emergence to reach maturity. Buckwheat also is very sensitive
to high temperatures and drying winds during blooming time in July and early August. Seedbed preparation
is similar to flax. Delayed sowing permits killing several weed crops prior to seeding. Presently, no
herbicides are labeled for use in buckwheat for weed control.

    Under good moisture and temperature conditions, buckwheat shades the ground rapidly. A seeding rate
of 40 to 50 lb/A is recommended. Seeding depth of 1 to 2 inches is desirable in moist soil. Shallow
seeding is desirable for rapid emergence. A conventional grain drill can be used and seed treatment
is not necessary. Buckwheat has limited response to fertilizers. It’s a heavy user of phosphate with needs
similar to wheat. Nitrogen application should remain low because of problems with lodging and
delayed maturity. Buckwheat should be swathed when most of the seeds are ripe. In the event of frost,
swath promptly to reduce shattering losses.

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

 

APPRAISING INJURY TO SMALL GRAINS

    There have been several reports of injury to small grains from herbicides. Leaf burn from herbicides,
or loss by mechanical means, during early stages most often has a minimal effect on yield; however, as
the crop approaches reproductive developmental stages, leaf damage or loss has greater impact on yield.

    Destruction of leaf area on young plants is seldom as serious as appearances may indicate. If the
growing point of small grain is not damagedm, plants will likely recover.

    During early development the growing point is below the soil surface, making it less susceptible
to injury. With this protection, small grains can suffer loss of above ground foliage without dying.
When hail, frost or herbicides cause severe foliar damage, it is advisable to wait several days after the
injury occurs to make an accurate determination of stand reduction. After this period, new growth
on plants with uninjured growing points can be observed. If no regrowth is observed, the stem of the plant
may be split to inspect the growing point. The growing point should be white or cream colored. Darkening
or softening of the growing point usually precedes plant death. When the growing point moves above the
soil surface at jointing in small grains it becomes more vulnerable to damage.

    Wheat and barley typically produce seven to nine main stem leaves. When leaf injury occurs at the
three to five leaf stage most tillers have at least two leaves that have not emerged and are undamaged.
The flag leaf, the last leaf produced on each tiller, is the most important leaf; if it remains undamaged
throughout the growing season the yield potential will be largely intact.

    When severe injury to small grains occurs after jointing, particularly from hail, plants still have
potential for recovery by initiating new tillers. Precipitation that usually accompanies hail storms will
help stimulate tillering. Potentially, tillering can restore yields to acceptable levels. The number of head
bearing tillers is determined before heading, so injury that occurs after heading in small grains is the most
damaging to yield.

Michael D. Peel
Small Grains Extension Agronomist
mpeel@ndsuext.nodak.edu

 

SCOUTING CORN AND SOYBEANS

    Efficient pest scouting in corn and soybeans requires knowledge of pest and crop biology, pest
identification and habits, correct sampling methods and a decision on economic thresholds. The goal
is to give an overview of crop condition with as complete, accurate and unbiased an assessment of
the pest problems in the fields as possible. In order to thoroughly overview your crops, keep in mind
the need for scouting frequency, scouting patterns across the field, field history, scouting reports,
equipment you should have on hand at all times, stand counts and general crop condition, specific
pest scouting procedures and any special problems that may be seen in the fields.

    Frequency of scouting depends on the crop and pests present or expected. Field corn often should
be monitored at least weekly until pollination is completed, at which time frequency can be relaxed to
once every ten days. Soybeans should be monitored at least once a week during the initial vegetative
stages and like corn this frequency can be relaxed after flowering begins.

    In order to clearly evaluate a field, use scouting patterns across each field for efficiency. An
"M-shaped" walking pattern in square or rectangular fields works best and in irregularly shaped
fields figure a pattern that covers a representative area of the field. Don't expect the edge of a field
to have the same pest populations as other areas. Don't sample field edges unless it is also specifically
needed such as with stalk borer or weed scouting. For large fields over 50 acres, consider splitting the
field into two or more separate scouted areas based on geography, previous cropping or soil type.

    Know as much about the field as possible before scouting. Besides field location, have cropping
history, crop yields, pesticide use, fertilizer applications, soil type, soil test records, major pest problems
in the past and anything else that can make your current job easier.

    Devise a scouting form to record your scouting finds. Even if pest damage is not found, record the
general crop health and growth stage. This will help you monitor changes in the field throughout the season.

    When monitoring corn and soybeans keep on hand the following equipment: scout forms, clipboard,
pencils, pocket knife (for splitting stalks and stems, looking at roots and cutworm scouting), magnifying
glass or hand lens for accurate pest identification, bags (as well as plastic vials and labels) for collecting
pest specimens for help in identification or later clarification, mechanical hand counter, measuring tape,
spade, cooler with ice in your vehicle to keep unknown pest samples fresh until identified as well as
reference materials in your vehicle in case questions come up in the fields.

    Stand counts in fields should be made the second week after crop emergence. Take counts for the
same distance in several locations within the field and determine by use of conversion factors the stand
on a per acre basis. If losses are seen later in the season, another stand count may be required. Evaluate
each field in order to keep on hand an accurate assessment of the crop stand.

    Consider the specific timing and requirements to scout weeds, diseases and insects. The first
weed survey should occur shortly after corn and soybean emergence and continue weekly until control
options are no longer available or until chemical and shading by the crop has clear control of weed
populations in a field. A comprehensive weed survey or map should be completed during and at the
end of the season in order to determine preventative weed control for the next season. Corn and
soybeans should be monitored for evidence of disease during each field visit. Know the general
conditions and time frames when certain diseases can occur. Check for specific diseases if they
have been found in nearby areas. Scouting for insects in corn and soybeans varies according to
insect species present. Familiarize yourself with the timing, habits and damage symptoms of insect
pests in your area. Use the specific scouting recommendations on each insect pest expected during
the time frames when these insects normally appear.

    Occasionally, unknown field problems are seen when scouting corn and soybeans. In these cases,
it is important to diagram where the problem occurred in the field and to collect plant samples so
proper identification can be made. Collect a variety of plant samples including roots and also collect
some healthy plants for comparison. Store samples in a cooler until they can be refrigerated or
identified through the diagnostic lab or other specialist. Include label information on the samples for
variety, planting date, environmental conditions, pesticide use, soil type, distribution of symptoms,
cropping history and any recent soil test results.

    Whether you are scouting your own fields or someone else's, determine your plan of covering
the acres you are scouting in as efficient a manner as possible. Also, keep in mind the many
resources available to you for additional information including your local county Extension agent,
other specialists, published reading materials (bulletins, fact sheets, newsletters and books) and the
Internet.

Denise A. McWilliams
Extension Crop Production Specialist
dmcwilli@ndsuext.nodak.edu

 


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