C.o.R.N. to go....
A Supplement to the OSU Extension Agronomic Crops Team Online C.O.R.N. Newsletter ~ This version for Ohio’s Country Journal is by Harold Watters
Why do we continue to have weed control problems?
I took this picture in Champaign the yield of soybeans. I know with the ad-
Table 1. Fall 2008 soybean harvest weed survey, con-
County but in my trips around western vent of Roundup Ready soybeans we have
ducted by these by county Extension personnel.
Ohio this spring I could have taken the a wonderful tool, but that program still has
same shot in any one of several other coun- limitations – so give glyphosate and
County Personnel
ties. I have seen a number of both corn and Roundup Ready soybeans the best start
Auglaize John Smith
soybean no-till fields without an at-plant you can.
Champaign Harold Watters
Clark Jonah Johnson
burn down. This picture shows a soybean So what happens if we don’t have our
Geauga, Ashtabula & Trumbull Les Ober
field with marestail (likely glyphosate re- weeds controlled starting at planting? A
Mercer Todd Mangen
sistant), large lambsquarters (at this size group of Agronomic Crops Team members
Miami Tim Fine
difficult to control with a normal rate of noted in Table 1, have been conducting fall
Montgomery Suzanne Mills-Wasniak
glyphosate) and mustards along with the weed surveys of soybean fields over the
Paulding Jim Lopshire
soybeans. past two to three years. This past fall we
Pickaway Mike Estadt
had the most counties and the largest area
Seneca Ed Lentz
surveyed ever. We each drive approxi-
Shelby Roger Bender & Woody Joslin
mately 80 miles in our county, observe
Union John Hixson
what weeds are above the canopy at har-
Van Wert Andy Kleinschmidt
vest and note the level of weed infestation.
The data presented in the tables repre-
Table 2. 2008 Ohio Soybean Harvest Weed Survey Sum-
sents observations made from over 1,200
mary – weed rank, % of fields found and % of fields with a
significant number of weeds
fields and 60,000 acres across Ohio. We
ranked the weeds in the field as a one (1) if
Weed % of fields % with score 2-3
there were a very few sporadic weeds –
Marestail 43.1% 13.6%
that’s what we normally expect, as a two
Giant ragweed 27.4% 8.0%
(2) if there were areas with several weeds in
Common ragweed 21.0% 5.8%
clumps and as a three (3) if weeds were
Common lambsquarters 16.1% 5.8%
widespread across the field.
Foxtail 14.4% 2.7%
Volunteer corn 12.5% 5.7%
Shown in Table 2 are the weeds we saw
My concern is that you can see in the most often and the level of severity. This is
above the soybean canopy at harvest. Now burndown that includes 2,4-D
picture just emerged soybeans and large basically the same list of weeds we have
I think it’s probably because we don’t do a • apply a pre-emergent herbicide that
weeds. I have worked on no-till soybean seen over the past three years. Some coun-
thorough enough job of weed control at covers a broad spectrum of weeds
weed control since the mid-1980s and we ties had levels of marestail (also known as
planting. When I asked Mark Loux, our • apply in-season post emergent weed
learned then, and it’s still a very good prac- horseweed) in as many as 75% of the fields
OSU Extension Weed Specialist, what we control, again broad spectrum in activity
tice, to start with a clean field for no-till in the county at harvest.
can do to prevent this problem, he sug- Check the OSU Weed Control Guide
soybean weed control. If weeds are given a For the past three years I have won-
gested we need to follow three methods of available from the OSU Extension offices
head start on soybeans, then they will be dered why we have marestail, giant rag-
attack to manage this problem: for assistance in choosing a weed control
able to out compete the crop and reduce weed and other weeds were standing
• provide seven days before planting a program.
oaRDC agronomic Crops Field Days
The Ohio State University Agronomic Pike, South Charleston, OH 45368. moment for participants with a more in- weather related injuries.”
Crops Team prides itself on delivering re- Jonah Johnson, OSU Extension Clark depth look at situations. By Peter Thomison – OSU Extension
searched-based agronomic information. We County, Harold Watters OSU Extension Topics for the Western Agronomy Corn Specialist
do the research in a number of places, in- Champaign County and Joe Davlin Field Day:   Certified Crop Advisor (CCA) and
cluding on cooperating farmer partner OARDC-Western Research Station Agrono- • “Integrated disease management in Commercial & Private Pesticide Applica-
fields throughout the state. We also partner mist have planned a full day of learning for Ohio corn production.” tor Training (PAT) credits will be avail-
with our sister organization The Ohio Agri- agricultural crops producers. The field day By Pierce Paul-OSU Extension Cereal able.
cultural Research and Development Center cost is $15.00 per person to cover lunch and Grains Extension Pathologist
Northwest Field Crops Day
(OARDC) based in Wooster. handouts. Contact Jonah in Springfield for • “Alfalfa fertility based on removal
OARDC is the research arm of the Col- reservations: rates and fertilizer sources.”  
The Northwest Field Crops Day will
lege of Food, Agriculture and Environmen- johnson.3225@cfaes.osu.edu. By Mark Sulc-OSU Extension Forage
be held July 30 from 9 a.m. to 11:30 p.m.
tal Science of The Ohio State University. The morning session will run from 9 Specialist
at the Northwest Research Station at 4240
State specialists work on the research sta- a.m. to Noon, with a wagon tour of the • “Field Crop Insect Update for 2009:
Range Line Rd, Custar, OH. If you want
tions and county level agricultural special- farm; there will be multiple stops at OSU Rootworms, Western bean
more information, please contact Matt
ists often do as well. For us on the Extension Research specialist/scientist’s cutworm and aphids.”
Davis, Northwest Farm Manager, 419-
Agronomic Crops Team we work most plots during the morning.  Each Specialist By Andrew Michel – OSU Extension
257-2060 or davis.1095@osu.edu for de-
closely with two research stations, the will discuss their research and topics of in- Specialist – Entomology
tailed information. Matt and the planning
Northwest Agricultural Research Station terest that pertain to this growing season. • “Mid-season Diagnostics; what to
committee always present a nice morning
near Custar, Ohio and the Western Agricul- At Noon, we will have lunch (must look for in foliar diseases and are we
visit with researchers, concerning crop
tural Research Station near South pre-register for lunch!). at risk for Asian soybean rust?“
development, pest problems and produc-
Charleston, Ohio. Both are planning field From 1 p.m. to 3 p.m. in the afternoon, By Anne Dorrance – Extension Spe-
tion research.
days for crop producers in July. July 22nd participants will have the option to visit cialist – Soybean Pathology
OARDC has a Web site for more infor-
at Western in South Charleston, and on July one of the OSU Extension specialist’s plots • “Cover crops and nitrogen manage-
mation: www.oardc.ohio-state.edu/,
30th at Northwest in Custar. for a more in-depth session where they can ment.”  By Robert Mullen – OSU Ex-
there is quite a bit of information here
Western Agronomy Field Day
walk through the plot and find and discuss tension Specialist – Soil Fertility
about the farms, the research and links to
issues that are currently occurring. There • “Weed control issues for 2009.”
the departments. The weather informa-
The Western Agronomy Field Day is
will be multiple locations across the farm By Mark Loux – OSU Extension
tion from the OARDC Web site:
slated for July 22, 2009 at Western OARDC
with different topics of interest to walk Weed Specialist
www.oardc.ohio-state.edu/newweather/
Research Station at 7721 South Charleston
through.  This should be a great learning • “How corn plants can recover from
is especially useful.
18Crops • Ohio’s Country Journal • July 2009
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