For growers in northern South Dakota and southern North Dakota, this August issue of Walking Your Fields newsletter contains articles about: ideal corn drydown and harvest timing, GDUs in the area and yield monitor calibration. Articles are written by DuPont Pioneer agronomists in South Dakota and North Dakota and are distributed on behalf of DuPont Pioneer account managers and Pioneer sales reps.

1. Cool August temperatures have been the topic of discus-
sion around the area. The cool temperatures have
slowed GDU accumulations and have resulted in below
average GDU accumulations to date. Fortunately, we still
have time in August and early September to gain valua-
ble GDU’s. Tracking GDU accumulation on your farm will
help estimate management windows and crop growth
stages.
Pioneer.com allows you to calculate GDUs for your spe-
cific location and planting date: https://www.pioneer.com/
home/site/us/agronomy/tools/gdu/
Many corn fields in the region were planted mid to late
May or early June, and that 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 decrease
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 drying 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. Upright ears are more
prone to capture moisture in the husks. Lastly, corn with
moderate test weight dries faster than hybrids with heavi-
er 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
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,
courtesy of your Pioneer sales professional. The DuPont Oval Logo is a registered trademark of DuPont. PIONEER® brand products are provided subject to the
terms and conditions of purchase which are part of the labeling and purchase documents. ®, TM, SM Trademarks and service marks of Pioneer. © 2013 PHII.
Corn Drydown & Harvest Timing
WALKING
YOUR FIELDS
®
www.pioneer.com
August 28, 2013 - Issue 5
Delaying harvest may increase risk of lodging, ear drop or kernel loss
and result in reduced yields. Photo: DuPont Pioneer
Growing Degree Unit Update
GDU Calculator
Location
2013 GDUs
Accumulated
5/1 - 8/20
2012
5/1 - 8/20
30
Year
Avg
+/- 30
Year
Avg
Aberdeen, SD 1739 2048 1905 -166
Brookings, SD 1729 2085 1822 -93
Faulkton, SD 1839 2117 2011 -172
Huron, SD 1839 2225 2086 -176
Lisbon, ND 1802 2068 1844 -42
Oakes, ND 1755 1996 1842 -87
Watertown, SD 1676 2032 1842 -166
Wahpeton, ND 1645 1925 1838 -193
>>

2. harvested 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).
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 below was developed
by Iowa State University, and customized with permission
by DuPont Pioneer agronomists to illustrate different dry-
ing 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.)
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. In a year with variability, taking
time to calibrate will pay big dividends!
Tips for yield monitor calibration
 Clear memory card and back up previous year’s data
 Calibrate multiple times throughout the growing season
to ensure consistent data
 Make sure 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
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
Calibrating Yield Monitors
AGRONOMY RESOURCES, TOOLS & APPS
Pioneer.com and Pioneer mobile allow growers to have extensive crop management resources and agronomy
information at their fingertips.
Pioneer®
Field360™ Tools app
Keep fields at your fingertips and capture important information with this GPS powered field documentation tool.
 Pinpoints your field location via satellite imagery and records notes or photos on the spot.
 Instantly organize your crop scouting information by location to save or share.
Pioneer®
Field360™ Notes app
Agronomy expertise from DuPont Pioneer in one app with field-level insights and real-time data.
 Input a location, start date and CRM one time and easily navigate between the enhanced agronomy tools.
 Track multiple field scenarios, view forecasts/daily precipitation, and calculate GDUs and key crop stages.
 Email results - including screenshots of graphs and estimated growth stages
Pioneer®
Field360™ Plantability app
This planter settings calculator gives precise planter settings for corn and sunflower seeds of all sizes and shapes.
Pioneer Planting Rate Estimator
Examine historical yield response curves to help estimate an optimum planting rate for Pioneer®
Brand Corn Prod-
ucts.

3. 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 Rep-
resentative if you
are willing to partic-
ipate in this test
and to answer any
questions you may
have. Again, we
are looking for lots
of grower participa-
tion to help us ad-
dress this question.
Goss’s wilt is beginning to show up in corn fields around
the central U.S. again this year. In 2012, the disease was
found throughout much of the area despite the dry condi-
tions in late summer and fall.
This season, high winds along with sand/soil blasting that
has occurred throughout June has likely created the kinds
of injury necessary for Goss’s wilt bacteria to enter corn
plants. The prolonged wet weather this spring is condu-
cive to bacterial diseases in many crops, and corn has
been no exception. Goss’s wilt is caused by a bacterial
pathogen and doesn’t respond to treatment with fungi-
cides. It is best managed with resistant hybrids and sound
cultural practices.
Typical signs and symptoms of Goss’s wilt
 Long, water-soaked, grayish-green patches or streaks
that turn to large dead streaks with wavy margins
 Dark ‘freckles’ within or just outside of leaf lesions
 Lesions appear to spread along leaf veins
(characteristic of bacterial disease)
 Yellow-orange bacterial ooze (or dried ooze appearing
as shiny flecks)
 Stems may become plugged with bacteria, vascular
bundles appearing orange to brown
The disease generally starts from inoculum surviving on
previous (corn) crop residues, found at or near the soil
surface. Early-season rainfall, especially when heavy or
associated with high winds can lead to infection of the
young corn crop. Early infection can produce the most
devastating symptoms, including wilting and early plant
death. Later infections typically affect leaves primarily, but
may lead to early maturity, or reduced ear size and lower
yields depending on the area affected and time of symp-
tom onset.
Risk factors to consider when planning for Goss’s
wilt management
 History of the disease in a field in last year or two indi-
cates presence of inoculum
 Continuous corn raises the risk of inoculum build-up
 Reduced tillage tends to lead to slower residue break-
down and greater risk that inoculum will remain in af-
fected fields
 Irrigated fields tend to have higher levels of disease
incidence and severity
As in-season management of Goss’s wilt is difficult or
impossible, be sure to select hybrids with the highest re-
sistance level available for areas that have multiple risk
factors mentioned above.
Early Harvest Challenge
Goss’s wilt symptoms on corn leaf. Photo: DuPont Pioneer
Goss’s Bacterial Wilt & Blight

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