This August issue of Walking Your Fields contains the following articles for growers in northern WI and northern MN: corn rootworm damage, late season soybean diseases and corn drydown and harvest timing. Articles are written by DuPont Pioneer agronomists in Minnesota and Wisconsin and are distributed on behalf of DuPont Pioneer account managers and Pioneer sales reps.

1. It has been a challenging growing season with the late
start and wet spring conditions. Drought conditions quick-
ly took over in mid-season. The August 13th U.S. Drought
Monitor Map for the Midwest shows drought affecting var-
ious parts of Minnesota and Wisconsin. Luckily, the cool
weather in early August allowed crops to survive with
minimal rain events but slowed development. At the end
of August, crop progress is still variable across the upper
Midwest but typically is delayed by 10-14 days. As of Au-
gust 18, most of central MN and northern WI accumulat-
ed 1500-1600 GDUs since mid May. We currently lag the
historical average by 100-200 for the shortened growing
season. We need to remain frost free into early October
to get the corn crop to naturally black-layer.
Producers should monitor fields
for root pruning from Corn root-
worm (CRW). Often root feeding
is discovered after a wind blows
over the damaged plants. Dam-
aged areas in the field typically
are not uniform and will result in
patchy areas of lodging next to
good standing corn. Rootworm
beetles are currently laying eggs
that will hatch into the root dam-
aging larvae in subsequent years. Northern CRW beetles
are green to yellow in color. Western CRW have yellow
and black stripes on their wings. Plan ahead for your
CRW strategy next year.
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 appear
due to toxins produced by
the root rotting fungus.
Split stems will generally
show only minor discolora-
tion in solid cortex areas,
with normal white pith.
Cool, moisture conditions early in the growing season
often results in higher disease incidence. Stress due to
heat and drought may reduce occurrence of SDS in some
cases.
Brown Stem Rot (Phialophora gregata) produces similar
striking leaf symptoms
mid-season as SDS,
which may cause con-
fusion of the two dis-
eases. Tissues be-
tween 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 infection
impedes the movement of water and mineral nutrients
needed for growth.
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Crop and Weather Update
WALKING
YOUR FIELDS
®
www.pioneer.com
August 28, 2013 - Issue 5
Corn Rootworm Damage Causing Lodging
Corn Rootworm Feeding
Photo: Clyde Tiffany
Late-Season Soybean Diseases
Figure 1. Leaf necrosis caused
by SDS or BSR. Photo: DuPont
Pioneer
Figure 2. Brown stem rot.
Photo: L. Osborne, DuPont Pioneer
<<

2. 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 harvest 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 apothecia(mushroom
like fruiting bodies) requires moist soil and a closed cano-
py. If surface soil moisture
is low or the soybean cano-
py is not closed during
flowering, the fungus would
not be able to produce apo-
theica. 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 can-
opy. The first evidence of
white mold is a chlorotic,
girdling lesion covered with
white, fluffy mycelium at
one of the middle nodes.
The evidence of the dis-
ease becomes conspicu-
ous 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 populations are high,
in narrow rows, in tightly closed canopies, where plants
become lodged and/or where less tolerant varieties are
planted.
Many corn fields in the region were planted mid to late
May or early June, this corn 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
Figure 3. Northern stem canker.
Photo: L. Osborne, DuPont Pioneer
Figure 4. White Mold
Photo: DuPont Pioneer
Corn Drydown & Harvest Timing
Delaying harvest may increase risk of lodging, ear drop or kernel loss
and result in reduced yields. Photo: DuPont Pioneer
>>

3. that the ideal moisture level for corn grain harvest is 25
percent. Harvesting wetter than that can damage kernels
and of course significantly increase drying costs (Nielsen
et al., 1996).
Artificial drying costs will vary this season depending on
LP gas prices, which currently ranges from $1.25 - $1.40
per gallon across Minnesota. Nonetheless, harvesting at
a higher moisture level this year may increase grower
profitability, specifically when growers anticipate medium
to high harvest losses. The table below was developed 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 sales representative for assistance.
(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.)
What is the ideal harvest moisture for corn grain? Or,
to be more specific, what grain moisture will provide the
greatest economic return to the grower?
This is a question that has been studied and debated
over the years, with some growers favoring earlier har-
vesting, while others prefer drier grain to minimize artifi-
cial drying. While there is no definitive answer to this
question, limited research, and some reliable on-farm
anecdotes suggest grower’s yield may “disappear” after
physiological maturity due to respiring grain in the field.
Additionally, field and harvest loss due to ear drop and
shelling may also impact harvestable yield.
To address this question, DuPont Pioneer is looking for
growers to run a simple test in their field this fall, compar-
ing a “early harvest” vs. “late harvest.” The test is easy to
do, and can be done with any corn hybrid:
1. Select a uniform field near bins or buildings that allow
for multiple harvests over time.
2. Harvest a portion of the field early, with grain mois-
tures near 25%.
3. Harvest a second time (or more) a week or more lat-
er, with final grain moisture targeted less than 20%.
4. Record harvest data with a yield monitor or weigh
wagon.
5. Note visible yield loss (dropped ears, etc.)
6. Provide harvest dates, yield & moisture data and
notes to your Sales Rep or DuPont Pioneer Agrono-
mist.
Contact your local Pioneer Sales Representative if you
are willing to participate in this test and to answer any
questions you may have. Again, we are looking for lots of
grower participation to help us address this question.
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 the 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!
AGRONOMY RESOURCES, TOOLS & APPS
Pioneer.com and Pioneer mobile allow growers to have
extensive crop management resources and agronomy
information at their fingertips. Check out these apps: Pio-
neer®
Field360™ Notes and Pioneer®
Field360™ Tools!
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
Early Harvest Challenge
Calibrating Yield Monitors

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