This issue of Walking Your Fields newsletter contains articles about: corn root lodging, soybean aphids and diseases, along with the role of water in corn development. Articles are written by DuPont Pioneer agronomists in Wisconsin and are distributed on behalf of DuPont Pioneer account managers and Pioneer sales reps.

1. Pioneer®
Field360™ Select software is an interactive,
web-based subscription service that combines your field
data with real-time agronomic and weather information.
 Track field by field Precipitation and GDUs using Field
360 Select
 Scouting 101 with GPS located as-planted Products
 On-The-Go organized field applied data
Pioneer Field360 Notes pinpoints your field location via
satellite imagery so you can record notes or photos on
the spot.
 Displays field boundaries for DuPont Pioneer custom-
ers
 Easy to use interface; available for iOS and Android™
 Instantly map and organize data with notes and pho-
tos
 Share your data from the field via email
Contact your local Pioneer Professional for more Info!
With the hot temperatures that we had in the last couple
weeks many growers are wondering where are we at
compared to normal? Below is the GDU information for
several different areas of Wisconsin. It is interesting to
note that we have several areas that are ahead of the
normal deviation.
We can start to make management decisions based upon
these GDUs with regards to insects and overall GDU
units to tassel and other significant effects in our cropping
system.
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.
WALKING
YOUR FIELDS
®
www.pioneer.com
July 24, 2013 - Issue 4
GDU Update
Growing Degree Units in Wisconsin
(May 1 - July 16, 2013)
GDU
Location
2012 2013 Vs. Normal
Appleton 1306 1053 -30
Chilton 1298 1057 28
Waupun 1333 1104 -14
Milwaukee 1348 1048 0
Madison 1463 1212 43
Platteville 1434 1228 10
Whitewater 1390 1134 6
Monroe 1510 1287 74

2. 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 the cause of lodging—don’t just assume it
is rootworm feeding.
Causes of Root Lodging in Corn
 Wet conditions at planting, causing sidewall compaction
and restricting root growth
 Wet conditions early in the growing season
 Strong wind and rain events during critical root develop-
ment 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
lodging due to
CRW feeding is
affected by the
timing of root
feeding, weather,
soil type and
hybrid type. Ex-
treme root lodg-
ing often results
from root feeding
by CRW larvae
in June, followed
by summer
storms. Once
rootworm larvae
have damaged
or destroyed
roots near the
soil surface, they
work their way
down the root
system. The later the root lodging occurs in the growing
season, the less able corn is to straighten up without pro-
nounced goose-necking. Closely monitor root lodged
fields and consider harvesting at higher moistures, if stalk
rot becomes an issue.
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
time.
Soybean aphids are right
on schedule and were re-
cently reported in southern
Wisconsin. Even if you
planted soybean seeds
treated with a nicotinoid
insecticide to delay aphid
population establishment,
you will still want to scout
your fields for this pest
from V5 through R5.
The soybean aphid over-
winters in buckthorn and
migrates to legumes
(soybeans, alfalfa and clo-
vers) 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.
Take Action Count the number of aphids on 30 to 50
plants throughout the entire field and calculate the aver-
age number of aphids per plant. If aphid populations
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 several bene-
ficial insects that feed on soybean aphids and can natu-
rally control the aphid population. They include Asian lady
beetles, damsel bugs, green lacewing larvae, and insidi-
ous flower bugs.
Root Lodging in Corn
Role of Water in Corn Development
Soybean Aphids
Photo: Marlin E. Rice
Corn rootworm damage reduces a
plant’s structural support and makes
it more susceptible 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.
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.
Photo:AaronPrestemon,DuPontPioneer

3. Bacterial leaf blight – Cool wet weather is the optimum
conditions for disease develop-
ment. Both brown spot and bacteri-
al leaf blight can be found on the
same plant. Leaves tend to appear
ragged as dead areas on leaves
will fall out as the leaf is retained.
Phytophthora Root Rot – Scout
one to two weeks after excessive
rains as phytophthora prefers
warm, saturated, compacted soil.
Phytophthora can be present from
VE through R6 growth stage, and it
displays seed rot, seedling blight
and root/stem rot phases.
Phytophthora can rot soy-
bean seeds and cause
damping-off which can be
diagnosed by the dark
brown discoloration of the
stem, usually beginning at
the soil line. Symptoms of
the root/stem rot phases
include a smaller than nor-
mal root mass and a dis-
colored tap root. By the
time you notice above-
ground symptoms like an
uneven, stunted stand, the
plant has already been
infected below ground for
several weeks. Plants may
also be light-green due to
minimal nodulations on the
roots. During later growth
stages, dark-brown to red-
brown lesions progress up
the stem from the roots.
Wilting and plant death
may soon follow, especial-
ly if the plant is stressed.
White Mold (Sclerotinia
Rot) – Sclerotinia white
mold is favored by cooler
night temperatures (50-60°
F) and moist conditions in
the plant canopy. In addi-
tion to cool temperatures,
the production of white
mold apothecia
(mushroom-like structures)
requires moist soil and a
closed canopy. If surface
soil moisture is low or the
soybean canopy is not closed during flowering, the fun-
gus would not be able to produce apothecia. When scout-
ing for this disease, pay attention to the fields that had
white mold previously and that have good soil moisture
and a closed canopy. The first evidence of white mold is
a chlorotic, girdling lesion covered with white, fluffy myce-
lium at one of the middle nodes. The evidence of the dis-
ease becomes conspicuous in August when dead tops
start to show up in fields. White mold is a disease of high
management. 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.
Sudden Death Syndrome (SDS) is a disease of growing
importance in Wis-
consin. Since its intro-
duction, it has contin-
ued to spread in the
state affecting more
and more acres.
Large yield losses
can be attributed to
SDS when infections
are severe. Symp-
toms typically show
up in July and August
even though the in-
fection occurred much
earlier in the year.
Though it is a root
disease, it is usually
identified by leaf
symptoms which
begin with scattered
yellow, diffused spots
between the veins.
The spots will continue to expand into brown lesions sur-
rounded by chlorotic areas. Leaves can dry up or curl and
will detach from the petioles as the disease progresses.
The pith of the stem will stay white, which will help distin-
guish SDS from brown stem rot, which can have similar
leaf symptoms. SDS does cause a root rot which may
have a surface blue fungal growth in moist conditions.
SDS often occurs in fields with an infestation of soybean
cyst nematode. Varietal resistance along with soybean
cyst resistance is the main method of management.
Fusarium Root Rot is a disease becoming more preva-
lent across the state. Plants suddenly die and when dug
up tap roots are
often rotted off.
Side hill areas
that are less well
drained are often
parts of fields
where Fusarium
is most noticea-
ble. There is no
known varietal
resistance to
Fusarium. Seed
treatments and
proper drainage
are key manage-
ment reminders.
Soybean Diseases
Plants wilting among healthy
plants is often a symptom of phy-
tophthora.
Photo: DuPont Pioneer
Photo:DuPontPioneer
Soybean plant showing symptoms
of white mold.
Leaf blight symptoms
Photo:DuPontPioneer
Sudden death syndrome symptoms
show up on leaves in July and August.
Photo:DuPontPioneer
Fusarium root rot. Photo: DuPont Pioneer

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