This July issue of Walking Your Fields contains the following articles for growers in northern WI and northern MN: a weather and area update, soybean aphids and cyst nematodes, corn root lodging and the role of water in corn development. 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. The 2013 planting season will go down as one of the
most difficult in many areas of Minnesota and Wisconsin.
At this point in the season, we hope the crops develop
rapidly enough to produce good quality grain or in some
cases enough quality forage for the livestock. Typically it
takes 55 to 60 days for grain corn to advance from tassel
to physiological maturity (black layer). However, harvest-
ing silage corn is earlier. Kernels will be at 50 percent
kernel milk about 42 to 47 days after tasseling. The re-
cent warm weather has increased optimism of hitting ma-
turity before frost. The map below shows the Growing
Degree Day accumulation across Minnesota and Wiscon-
sin from May 15 to July 15. A typical 95 RM hybrid will
need 2200 GDDs from planting to P.M.
Pioneer recently realigned territory lines to improve cov-
erage; therefore some staff have new territories. No mat-
ter their location, our Dairy Specialists, Account Manag-
ers, Agronomists and Sales Representatives pledge to
provide you with the best information and excellent ser-
vice that you have come to expect from Pioneer®
.
New assignments include:
Matt Laubauch– Dairy Specialist for Central MN
Ryan Bates – Field Agronomist for NE and Central WI
Clyde Tiffany – Field Agronomist for NW WI and C. MN
Mark Navara – Account Mgr. for East Central MN
Marty Lovrien – Account Mgr. for Central MN
Soils with low or-
ganic matter levels
and fields with ex-
cess water satura-
tion will benefit
from planned or
rescue top dress-
ing of nitrogen and
sulfur. Typically,
the biggest re-
sponse occurs
when applications
are done before
the corn is 12-18‖
tall. However,
weather conditions
forced some later
applications. Often
30-50 pounds/acre
of supplemental N is adequate to offset lost nitrogen.
Soybean aphids are
right on schedule and
were recently report-
ed in central Minne-
sota. Even if you
planted soybean
seeds treated with a
nicotinoid insecticide
to delay aphid popu-
lation establishment,
you will still want to
scout your fields for
this pest from V5
through R5.
The soybean aphid
overwinters in buck-
thorn and migrates to
legumes (soybeans, alfalfa and clovers) in July. It’s less
than 1 mm in length but when left untreated, economic
infestations can reduce yields by more than 10 bushels/
acre.
Symptoms Aphid-infested soybean plants may look simi-
lar to a potassium deficiency: curled leaves, often yellow
on the outside. Aphids produce a sugary excrement,
Area & Weather Update
WALKING
YOUR FIELDS
®
www.pioneer.com
July 24, 2013 - Issue 4
DuPont Pioneer Territory Adjustments
Supplemental Nitrogen Valuable
Soybean Aphids
Nitrogen and sulfur topdressing were criti-
cal this year with the excess precipitation.
Photo: Clyde Tiffany, DuPont Pioneer Agronomist
Soybean aphids and an ant on a soy-
bean leaf. Aphids excrete ―honeydew,‖ a
sugary substance that attracts other
insects and also results in development
of sooty mold.
Photo: Marty Lovrien, DuPont Pioneer
>>
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.

2. known as honeydew, on leaves, which promotes soot
mold growth and can serve as a feeding ground for ants.
Plants infested by the soybean aphid will also appear
shorter.
Besides a stunted plant
with noticeable discolora-
tion, you can also detect
these oval-shaped, light
green pests with black
―tail pipes‖ near the end
of the abdomen by doing
numerous sweeps
through the field.
Take Action Count the
number of aphids on 30
to 50 plants throughout
the entire field and calcu-
late the average number of aphids per plant. If aphid pop-
ulations reach 250 per plant and are increasing during
the R1 – R5 growth stages, consider a foliar insecticide to
control the population. Your local Pioneer sales rep can
help with product recommendations. There are also sev-
eral beneficial insects that feed on soybean aphids and
can naturally control the aphid population. They include
Asian lady beetles, damsel bugs, green lacewing larvae,
and insidious flower bugs.
Soybean cyst nema-
tode (SCN) race
shifts and high cyst
counts are an added
stress to soybean
fields. Planting SCN-
resistant soybean
varieties that include
the Peking and
PI88788 source of
resistance, along
with rotating to a non
-host crop are two of
the best ways to
prevent SCN infesta-
tions. Extension spe-
cialists have advised that the overuse of any single
source of SCN resistance can lead to SCN race shifts
over time. Therefore, it is important to switch between
varieties and always scout fields.
To scout for SCN, dig up soybean roots and gently wash
the soil away. If you don’t see a high number of SCN,
recheck in two weeks to make sure you are not between
production cycles.
DuPont Pioneer offers both the Peking and the
PI88788 source of resistance. Take time to dig and
compare the female cysts numbers between the Peking
and PI88788 sources.
When SCN becomes prevalent, it also promotes the de-
velopment and spread of Sudden Death Syndrome and
increases the severity of Brown Stem Rot.
Below are recommendations from the Plant Health Initia-
tive funded by the Soybean Checkoff on crop and soy-
bean resistant variety rotation:
 Rotate with non-host crops to reduce SCN numbers.
 Rotate with resistant soybean varieties to reduce yield
loss due to SCN.
 Rotate the resistant varieties you use: don’t use the
same one twice in a row.
 Rotate with tolerant or susceptible soybean varieties
only if SCN numbers are low.
More information about SCN resistant varieties and SCN
damage is available through you local Pioneer sales rep
and also available in the Soybean Cyst Nematode Man-
agement Guide: http://www.planthealth.info/pdf_docs/
SCNGuide_5thEd.pdf
Extreme, early-season moisture, strong wind events and
corn rootworm feeding all contribute to increased poten-
tial of corn root lodging. If root lodging has occurred, take
time to assess its cause—don’t just assume it is root-
worm feeding.
Causes of Root Lodging in Corn
 Wet conditions at planting, causing sidewall compac-
tion and restricting root growth
 Wet conditions early in the growing season
 Strong wind and rain events during critical root devel-
opment and prior to brace root formation
 Reduced root growth due to nitrogen deficiency
 Hybrid differences in root formation
 Corn rootworm (CRW) feeding
Yield loss and lodg-
ing due to CRW
feeding is affected
by the timing of root
feeding, weather,
soil type and hybrid
type. Extreme root
lodging often results
from root feeding by
CRW larvae in
June, followed by
summer storms.
Once rootworm lar-
vae have damaged
or destroyed roots
near the soil sur-
face, they work
their way down
Soybean Cyst Nematodes
Root Lodging in Corn
Photo: Bruce Carlson
Soybean aphid damage on soy-
bean leaves.
Photo: DuPont Pioneer
Female cysts of SCN on plant roots.
Photo: Marlin E. Rice
Corn rootworm damage reduces a plant’s
structural support and makes it more sus-
ceptible to lodging. CRW injury to nonBt
corn roots on left compared to Bt hybrid
on the right. Taken from an Iowa State
University research plot.>>

3. the root system. The later the root lodging occurs in the
growing season, the less able corn is to straighten up
without pronounced goose-necking. Closely monitor root
lodged fields and consider harvesting at higher moistures,
if stalk rot becomes an issue.
Water is essential to corn growth, especially at tasseling
when the corn’s uptake of water increases dramatically.
From now through the dent stage, corn demands an aver-
age of a ¼ inch of water per day. Inability to receive this
amount of water can lead to decreased yields.
Root growth can help compensate for the increased water
need, as the expansion of the root system reaches deep-
er into the soil profile to help the plants extract more soil
moisture. However, air temperatures also greatly influ-
ence water needs. Temperatures in the 90s during corn
growth will double the corn water requirement when com-
pared to temperatures in the 60s. Water stress impacts
corn yield the most during pollination, followed by grainfill
and vegetative growth stages.
Irrigation is an option to optimize yields. Checking your
fields using probing methods is important as irrigation
must be started early enough to fully benefit the crop and
increase yield potential. Most irrigation systems cannot
keep up with crop water demands during the later critical
growth periods (VT to R3). The first priority for irrigation
should be a 3-week period starting just before tassel (VT)
and ending just after silking. Corn is less susceptible to
water stress during later grain-development stages (R3).
Soil water levels should be maintained to allow the crop
to reach maturity (R6).
Understanding Water Usage in Corn
Water is acquired, used and lost through evapotranspira-
tion (ET). In this process, water is removed directly from
the soil surface to the atmosphere by evaporation and
through the plant by transpiration. Plant transpiration is
the evaporation of water from leaf and other plant surfac-
es. For corn, evaporation often accounts for 20 to 30 per-
cent and transpiration 70 to 80 percent of total ET over
the length of a growing season.
The amount of water
retained for the plant
is affected by the soil
texture and organic
matter. Soil serves as
a reservoir to the
plant, even though
not all water is acces-
sible to the plant.
Water held by the soil
between field capaci-
ty and permanent
wilting point is called
―plant-available wa-
ter‖ and varies by soil
texture. Ranges of
available water at fine sandy soil are 0.7 to 1 inch, in-
creasing up to clay which holds 1.8 to 2.4 inches.
Pioneer®
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Pioneer Field360 Notes pinpoints your field location via
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the spot.
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ers
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Contact your local Pioneer Professional for more Info!
Role of Water in Corn Development
Table 1. Estimated Corn Evapotranspiration and Yield
Loss per Stress Day During Various Growth Stages
Growth Stage
Evapo-
transpiration*
(inches/day)
% yield loss per
day of stress
(min-ave-max)
Seedling to 4 leaf 0.06 ---
4 leaf to 8 leaf 0.10 ---
8 leaf to 12 leaf 0.18 ---
12 leaf to 16 leaf 0.21 2.1 - 3.0 - 3.7
16 leaf to tasseling 0.33 2.5 - 3.2 - 4.0
Pollination (R1) 0.33 3.0 - 6.8 - 8.0
Blister (R2) 0.33 3.0 - 4.2 - 6.0
Milk (R3) 0.26 3.0 - 4.2 - 5.8
Dough (R4) 0.26 3.0 - 4.0 - 5.0
Dent (R5) 0.26 2.5 - 3.0 - 4.0
Maturity (R6) 0.23 0.0
Adapted from Rhoads and Bennett (1990) and Shaw (1988). From: What
Happens Within The Corn Plant When Drought Occurs? Joe Lauer, Uni-
versity of Wisconsin-Extension, 2003.
*Evapotranspiration is the total of the water used by the corn plant
and water lost to evaporation.
Image 1. Evapotranspiration is the sum
of evaporation from the land’s surface +
transpiration from the plant. Image:
SalinityManagementGuide.org

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