VOLUME 5 • ISSUE 5 • MAY 2010
Agronomy Update
is a monthly
publication provided
to producers free of
charge. AgVenture,
Inc. and it’s
independently owned
and operated
Regional Seed
Companies are
dedicated to
providing producers
exceptional seed
products; genetics
and technologies, and
professional service
and local knowledge
of agronomic
conditions impacting
producer profitability.
Grow with
Confidence!
Warm, Dry Conditions Influence Drift Growers preparing to
spray may want to take a fresh look at the effect of temperature
and humidity on pesticide drift. In warmer weather and lower
humidity, faster evaporation occurs – causing spray droplet size
to decrease. Smaller droplets are more susceptible to moving off
target as they enter the air currents and are
moved by wind. Iowa State University research
shows that at a 50-degree air temp, an 80
percent relative humidity and a 10mph wind,
roughly 1 percent of spray volume will drift 30
feet away from the nozzle. As temperatures
increase and humidity decreases, spray drift
increases significantly.
The graph shows the effects of crosswind
speed and air conditions (80% r.h. at 50
degrees; 40% r.h. at 86 degrees) on drift
distance for percentage of spray volume exiting
an 8004 flat-fan nozzle at 40psi. http://www.extension.iastate.edu/CropNews/2009/0611schaefer.htm
Assure Sound Soybean Stands The soybean
plant has an amazing ability to compensate for
low plant populations and gaps in the row, but
poor stands can cause potential yield loss. To
determine plant population, use a hula hoop or
make your own from an old piece of garden hose.
The chart provided helps calculate plant stand.
Planning for Foliar Fungicide Application?
Inside Diameter of Hoop
No. of
Plants
30in
5
53
32in
34in
36in
38in
Plants (1000/acre)
47
41
37
33
10
89
78
69
62
55
14
124
109
97
86
77
18
160
140
124
111
100
22
196
172
152
136
122
Many growers are considering a foliar fungicide
26
231
203
179
160
144
application this season. Most fungal diseases
overwinter on crop residue. With heavy residue
present in many fields due to a late 2009 harvest, there is a high likelihood that disease could
develop again this summer. One example is gray leaf spot, a perennial and economically
damaging fungus. AgVenture encourages growers to monitor corn plants for small, pinpoint
lesions surrounded by a yellowish halo. Scouting and proper diagnosis are always the first lines
of defense before determining economic thresholds for any fungicide application.
Nationwide, there has been a big upturn in the use of foliar fungicides. While they help control
disease, research continues to evaluate how and if fungicides containing a strobilurin mode of
action may have positive physiological effects on the plant that are sometimes attributed to
increased yield. Talk with your AgVenture RSC to learn how fungicide applications have been
working in your area.
©AgVenture,
Inc. 2010
AgVenture, Inc.
is the nation’s largest
network of
independently owned
regional seed
companies. Based in
Kentland, Indiana,
AgVenture provides a
growing network of
independently owned
and managed regional
seed companies with
seed products meeting
exacting standards for
quality, together with
leading-edge genetics
and technology.
Since 1983, this unique
marketing approach
has allowed each
individual company to
match the hybrids it
sells to the specific
needs of the
geographical area it
serves. Combined with
professional seed
representation at a
local level, AgVenture
strives to help every
grower realize more
profit from every field.
Grow with
Confidence!
Herbicide Activity Affected by Hard Water A recent study released by Purdue weed
scientists shows that hard water can have a dramatic effect on herbicide activity. Glyphosate
efficacy is antagonized when it is tank-mixed with some Manganese (MN) fertilizers and MnEDTA appears to be the least antagonistic of the Mn fertilizers.
Growers note that Manganese deficiency is occasionally observed in soybeans with symptoms
frequently appearing near the time of postemergence glyphosate applications. In
glyphosate-resistant soybean, producers and
custom applicators occasionally tank-mix
glyphosate and foliar Mn fertilizer to reduce
application costs. The study results
encourage growers to add ammonium sulfate
to the tank before herbicides are added to
reduce the effect of hard water cations on
glyphosate efficacy. Also, Mn EDTA is less
antagonistic to glyphosate than Mn sulfate.
However, both can reduce glyphosate efficacy on velvetleaf and waterhemp. Source:
http://www.btny.purdue.edu/weedscience/2010/GlyphosateFertilizers.pdf
Brown Stink Bug Scouting in Progress Across the Mid-South, scouting
for Brown Stink Bug has begun, even though they can be tricky to find.
Check the corn plant whorls, sides of the stem and at the base of the plant.
Monitor field edges that border trees or CRP type areas. A typical infestation
of 10% on plants up to 2 feet tall warrants treatment. Stinkbugs can often
result in stunted plant growth. Check with your AgVenture RSC to determine
thresholds. (Photo Mississippi State)
Slug Hatch Under Way Slug egg hatch has begun in some southern and eastern corn fields.
Slug eggs are usually laid in batches of 3-5 and are found slightly below the soil surface. If
damage is suspected, growers are encouraged to move crop residue aside in about a foot
square area, scrape the soil with a small knife or other instrument to look for newly hatched
slugs. Check 20 plants in each of five areas in the field for damage.
Heavy crop residue is a great host for slugs. Zone tillage or row sweepers at planting may
reduce slug damage by encouraging corn growth and soil drying. Early planting and crop
emergence before the spring egg hatch will allow most seedlings to get beyond corn's
vulnerable stage. Poorly sealed seed slots can result in severe slug damage and crop stand
losses. Where replanting is necessary, the field or area damaged should be tilled first to disrupt
the slugs' environment.
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