Learn about late season soybean diseases, yield monitor calibration tips and guidance on corn drydown and harvest timing in this August issue of Walking Your Fields newsletter. Articles are written by DuPont Pioneer agronomists in South Dakota and distributed on behalf of DuPont Pioneer account managers and Pioneer sales reps.

1. In a stressful growing season, attack from plant patho-
gens may begin to show up late in the year as patches of
dying or wilted plants with drooping or diseased leaves.
While soybean diseases may become apparent just prior
to harvest, the infection may have occurred much earlier
in the season. These above-ground symptoms are com-
mon to several unique below-ground problems. A quick
peek at roots and lower stems can help determine which of
these pathogens might be at work in your soybean fields.
Proper identification can help with future variety selection
and management decisions.
Sudden Death Syndrome (Fusarium virguliforme)
produces striking leaf symptoms (Figure 1), which alert us
to problems in the
roots. Affected plants
may die rapidly after
first leaf symptoms ap-
pear due to toxins pro-
duced by the root rot-
ting fungus. Split stems
will generally show only
minor discoloration in
solid cortex areas, with
normal white pith. Cool,
moisture conditions
early in the growing
season often results in
higher disease inci-
dence. Stress due to heat and drought may reduce occur-
rence of SDS in some cases.
Brown Stem Rot (Phialophora gregata) produces similar
striking leaf symptoms mid-season as SDS, which may
cause confusion of the two diseases. Tissues between
veins become yellow and quickly turn brown, except for a
narrow band of green tissue outlining the vein. However,
BSR is distinguished
from SDS and other
diseases by brownish
discoloration due to
an infection of the pith
tissue in lower stems
(Figure 2). This infec-
tion impedes the
movement of water
and mineral nutrients
needed for growth.
Northern Stem Canker (Diaporthe phaseolorum) is a re-
emergent soybean disease that begins at points along
lower stems, creating brownish-red lesions (cankers) ex-
tending part way around and into lower stems (Figure 3).
Affected plants
often retain
dead leaves
even up to har-
vest time.
Roots and pith
(the soft center
are of stems)
are generally
not affected by
stem canker.
White Mold (Sclerotinia Rot) Sclerotinia white mold is
favored by cooler night temperatures (50-60°F) and moist
conditions in the plant canopy. In addition to cool temper-
atures, the production
of white mold apothe-
cia requires moist soil
and a closed canopy.
If surface soil moisture
is low or the soybean
canopy is not closed
during flowering, the
fungus would not be
able to produce apo-
thecia. When scouting
for this disease, pay
attention to the fields
that have a history of
white mold and fields
that have good soil
moisture and a closed
canopy. The first evi-
dence of white mold is
a chlorotic, girdling
lesion covered with
white, fluffy mycelium at one of the middle nodes. The
evidence of the disease becomes conspicuous in August
when dead tops start to show up in fields. It is most likely
to show up in low spots of the field where plant popula-
tions are high, in narrow rows, in tightly closed canopies,
where plants become lodged and/or where less tolerant
varieties are planted.
WALKING YOUR FIELDS® newsletter is brought to you by your local account manager for DuPont Pioneer. It is sent to customers throughout the growing season,
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Late Season Soybean Diseases
WALKING
YOUR FIELDS
®
www.pioneer.com
August 28, 2013 - Issue 5
Figure 3. Northern stem canker.
Photo: L. Osborne, DuPont Pioneer
Figure 1. Leaf necrosis caused by
SDS or BSR. Photo: DuPont Pioneer
Figure 2. Brown stem rot.
Photo: L. Osborne, DuPont Pioneer
Figure 4. White Mold
Photo: DuPont Pioneer

2. Yield information from monitors and GPS is an
extremely important tool that you can use to make deci-
sions in your business. However, it is only as accurate as
the calibration and taking time to do this will help elimi-
nate poor information later. Here are some tips to remem-
ber when looking at yield monitor calibration:
 Clear memory card and back up previous year’s data
 Calibrate multiple times throughout the growing sea-
son to ensure consistent data
 Make sure your load is enough weight (3,000-6,000
pounds)
 Make sure you have multiple loads at different
speeds (3.5, 4.5, 5 etc.)
 Calibration loads should be in a uniform area of the
field, a good representation will improve accuracy
 Differences in moisture and grain quality will require a
new calibration to be accurate
In a year with variability, taking time to calibrate will pay big
dividends!
Many corn fields in the region were planted mid to late
May or early June, which means they will likely need until
early October to reach maturity (black layer). As growers
hope for a late autumn to get field work done before the
snow flies, now is the time to weigh the cost of in-field
grain drydown versus using artificial drying at harvest.
There are three main factors that influence the rate at
which corn dries, physiological maturity, weather and the
corn hybrid. Corn that matures earlier typically dries fast-
er due to more favorable drying conditions earlier in the
harvest season. On the same note, later maturing corn
has fewer warm days to aid drying and will dry slower. In
a typical year, corn that matures on September 15 may
require only about 10-15 days to reach 20 percent mois-
ture, while corn that matures on September 25 may need
30 days to reach the same moisture level (D.R. Hicks,
2004). Drydown is linked to heat units (GDUs). Under
ideal weather conditions, corn may lose up to one point of
moisture per day. As the days get cooler, GDUs de-
crease and drying slows. A rule of thumb is that 30 GDUs
are required to lower the grain moisture each point from
30 percent to 25 percent. Forty-five GDUs per moisture
point are required from 25 percent to 20 percent. Also
consider that we typically expect no more than about 10
GDUs per day in late September, and only about 3-5
GDUs per day in late October. That means that field dry-
ing of corn may take two to three times longer for late
maturing fields. Drydown is also hybrid specific. The
amount, thickness and tightness of husks affect drydown;
the more insulated the ear, the longer it takes to dry. Up-
right ears are more prone to capture moisture in the
husks. Lastly, corn with moderate test weight dries faster
than hybrids with heavier test weights.
The ideal harvest moisture for corn is between 22-25 per-
cent. Waiting for corn to dry to 18 percent moisture in the
field certainly saves on the energy bill; but it also increas-
es the likelihood of excess harvest losses due to stalk
lodging, ear drop and detrimental weather all of which
can affect your bottom line. In addition, there may not be
enough heat units this fall for in-field drydown. Ohio State
University research indicated no additional in-field grain
drying occurred after early to mid-November (Minyo,
Geyer & Thomison, 2009).
“Phantom yield loss” may also encourage growers to har-
vest at slightly higher moistures this fall. Growers occa-
sionally report harvesting part of a field early and finishing
the field when it is dryer, only to discover the later har-
vested portion of the field is yielding several bushels less
per acre than the first harvested corn.
Purdue University confirmed these claims indicating that
grain corn dried in the field has the potential to yield one
percent less per point of moisture. For example, corn that
was 200 bushels/acre at 28 percent moisture would only
yield around 180 bushels/acre at 18 percent moisture if
left in the field too long. This research also confirmed that
the ideal moisture level for corn grain harvest is 25 per-
cent. Harvesting wetter than that can damage kernels
and of course significantly increase drying costs (Nielsen
et al., 1996).
Calibrating Yield Monitors
Corn Drydown & Harvest Timing
Estimated Cost to Dry Corn to 15% Moisture
Harvest
Moisture
LP
gal/bu
LP
$/gal
LP
$/bu
Drying Cost
$/bu*
Drying cost
$/point*
35 0.472 1.35 0.637 0.645 0.032
30 0.337 1.35 0.455 0.461 0.031
25 0.219 1.35 0.296 0.299 0.030
20 0.109 1.35 0.147 0.149 0.030
Based on: NCH-51 Hybrid Maturity-Energy Relationships in Corn
Drying, Iowa State University; *assumes electrical cost of $0.115/kwh
Delaying harvest may increase risk of lodging, ear drop or kernel loss
and result in reduced yields. Photo: DuPont Pioneer
>>

3. Artificial drying costs will vary this season depending on
LP gas prices, which currently range from $1.25 - $1.40
per gallon across the Midwest. Nonetheless, harvesting at
a higher moisture level this year may increase grower
profitability, specifically when growers anticipate medium
to high harvest losses. The table on page two was devel-
oped by Iowa State University, and customized by
DuPont Pioneer agronomists to illustrate different drying
scenarios and costs based on an average LP price of
$1.35/gallon.
If you have questions about moisture levels, drydown and
harvest, contact your local sales representative for assis-
tance.
(Sources: Minyo, Geyer & Thomison. 2009. How will delaying corn har-
vest affect yield, grain quality and moisture? Ohio State University Ex-
tension. Nielsen et al. 1996. Kernel dry weight loss during post-maturity
drydown intervals in corn. Purdue University.)
The results of the fall 2011 tillage are evident in the 2012
crop. Particularly in corn on corn cropping systems. Fall
2013 is shaping up to be a similar environment and may
present some of the same opportunities and challenges.
It may be helpful to review and adapt for this environ-
ment.
Challenges of 2011 Primary Tillage
 Hard, dry soil led to equipment stress, frequent
breakdowns, and dramatically increased wear on soil
contacting blades and points.
 Primary tillage standards on many makes and models
are set up on wide spacing (30”). To increase residue
coverage many are equipped with wings on the
points. These wings on wide spacing can cause large
boulders of soil and eventually seedbeds that exhibit
areas of loose dry soil intermingled with firm moist
conditions.
 Too much speed. To fracture the soil and form con-
sistently sized chunks that are field level, we may
need to reduce ground speed to 4.5 to 5 mph. Each
soil and type of tillage equipment is different, but
slowing down may improve the results.
Opportunities for Tillage in a Dry Soil
 Primary tillage is most effective at lifting soil compact-
ed layers and producing an even shattering effect
across the width of the tillage tool.
 Soil smearing with ground contacting points is mini-
mized
 Leveling devices on primary tillage tools may work
more effectively.
 Appropriate levels of residue incorporation can be
accomplished which increases soil to residue contact
enhancing residue breakdown without layering resi-
due and causing seedling residue interactions (corn
on corn concern)
 Residue sizing and corn root ball management can
be more effective with the use of corn head choppers
or stalk choppers combined with vertical tillage tools
prior to primary tillage.
 Deep tillage will not ‘dry out your soils’.
 Make every attempt to incorporate and reduce large
residue for next spring planting.
Will Fall Tillage be Similar to 2011?
Large depressions from primary tillage. In this case there is
a 12” difference between the high and the low behind the
digger. In a spring like 2012 where the conditions were dry
this may lead to areas of dry loose soil slumping into the
depressions in contrast to the firm moist areas. This can
lead to planter performance issues on planting depth and
seed drop due to engagement of gauge wheels. This then
leads to differing emergence rates due to seed-to-soil con-
tact and water uptake into the kernel. In a wet spring and
summer, these factors are less of a problem.
Photo: Kimberly Ag Consulting. Maxwell, IA.
Variable ear placement and ear sizes based on emergence
timing and interaction of seedlings with residue in the de-
veloping root system. By digging up runt plants and com-
paring to larger better developed neighbors you can start to
understand causes of delayed emergence or delayed
growth. Photo: Kimberly Ag Consulting. Maxwell, IA.

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