C.O.R.N. Newsletter : 2018-11

  1. What a difference a month makes!

    Author(s): Jim Noel

    After a cold and wet April, May is shaping to have temperatures normal or slightly warmer than normal with rainfall near normal.

    Except for rainfall later this week (with best chances north of I-70) rainfall will be at or below normal for the first half of May. The exception will be the northern tier of counties in Ohio which should at least get normal rainfall maybe a bit above.

    It does appear the second half of May will turn somewhat wetter which should cause May to average out the drier and wetter patterns to near normal rainfall.

    With more drying and warmer temperatures, that is some good news in Ohio for getting crops going in a big way.

    The NOAA/NWS/OHRFC 16-day rainfall maps shows the highest risk area for 2-4 inches of rain the next few weeks from extreme northern Ohio into northern Indiana back into Illinois and Iowa.

  2. Adjusting no-till burndown programs for a prolonged wet spring

    Author(s): Mark Loux

    This is a revision of an article we seem to publish in C.O.R.N. about every three years, when wet weather prevents early planting and in some cases also prevents early burndown applications.  Not a lot of either has occurred yet, although it’s starting to dry out and warm up.  The good news is that cool weather has slowed weed growth, but even so, the weeds obviously continue to get bigger under wet conditions, and what is a relatively tame burndown situation in early to mid-April can become pretty hairy by early to mid May.  One issue with later burndowns certainly is that there can be a need for a more aggressive herbicide mix, but also a need to plant as soon as possible, and these can be conflicting goals.  For example, unless dicamba is an option, we would say keep 2,4-D ester in the mix if at all possible, but this means waiting 7 days to plant. 

    Marestail is always one of the bigger concerns in a late burndown situation, especially overwintered plants in fields that were not treated last fall.  Many of the other weeds, even if bigger, are still relatively well controlled by minor modifications to standard burndown programs (e.g. higher glyphosate rates, adding another herbicide).  Overwintered marestail get tougher to control with increased size and age, to the point that they will reach a size and age where a mixture of glyphosate and 2,4-D often won’t work.  Substituting Sharpen for the 2,4-D can improve control usually, but even this combination is not infallible as marestail gets larger.  Also – we have observed some weakness from the glyphosate/Sharpen combination on dandelion, purple deadnettle, and larger giant ragweed.  The more effective approach is to combine all three herbicides – glyphosate, 2,4-D and Sharpen.  It’s good to have Xtend soybeans and dicamba in the toolbox in this situation.  Glyphosate plus dicamba is more consistently effective than glyphosate plus 2,4-D for control of overwintered marestail.  The addition of metribuzin to any of these can also result in more consistently effective marestail control.  Having said all of this, we find marestail to be mostly absent this year in many of our research fields, so some scouting may help with burndown decisions.

    Some things to consider in a delayed burndown situation:

    1.  Increase glyphosate rates to at least 1.5 lb ae/A.  This will not improve marestail control, but should help with most other weeds. 

    2.  Where at all possible, keep 2,4-D ester in the mix, even if it means waiting another 7 days to plant soybeans.  Plant the corn acres first and come back to soybeans to allow time for this.  Have the burndown custom-applied if labor or time is short. 

    3.  To improve control with glyphosate/2,4-D, add Sharpen or another saflufenacil herbicide, as long as the residual herbicides in the mix do include flumioxazin, sulfentrazone, or fomesafen if it’s within 14 days of soybean planting.  It’s also possible to substitute Sharpen for 2,4-D when it’s not possible to wait 7 days to plant, but this may result in reduced control of dandelion, deadnettle and giant ragweed.  Where the residual herbicide in the mix does contain flumioxazin, sulfentrazone, or fomesafen, and it’s not possible to change the residual or add Sharpen, adding metribuzin can improve burndown effectiveness somewhat.

    4.  Deciding to include Sharpen at the last minute can result in a need to alter the residual herbicide program.   Labels still allow mixtures of Sharpen with herbicides that contain flumioxazin (Valor), sulfentrazone (Authority), or fomesafen (Reflex) only if applied 2 or more weeks before planting.  Where these are replaced by a metribuzin-containing herbicide or mix such as Canopy or Zidua Pro/metribuzin, add enough metribuzin to get the rate to the equivalent of 8 to 12 oz/A of metribuzin 75DF.

    5.  Consider substituting Gramoxone or glufosinate for glyphosate?  Gramoxone is   less effective than glufosinate on marestail, but the mix of Gramoxone/metribuzin/2,4-D controls marestail well unless they are big.  Omitting 2,4-D from this mix because of planting considerations reduces it from an excellent/good treatment to fair/good.  Glufosinate can struggle some in a dense, large no-till burndown situation, and should also be applied with metribuzin and 2,4-D ideally.  Use the higher labeled rates and a spray volume of 15 to 20 gpa for best results.  A consideration here is that in large no-till weed situations, high rates of glyphosate typically have more value than high rates of Gramoxone or glufosinate, with the exception of glyphosate-resistant weeds.

    6.  Among all of the residual herbicides, chlorimuron contributes the most activity on emerged annual weeds and dandelion.  This is probably most evident when the chlorimuron is applied as a premix with metribuzin (Canopy/Cloak DF, etc).  The chloirmuron may not be much of a help for marestail control, since many populations are ALS-resistant.  Cloransulam (FirstRate) has activity primarily on emerged ragweeds and marestail, as long as they are not ALS-resistant.  We have on occasion observed a reduction in systemic herbicide activity when mixed with residual herbicides that contain sulfentrazone or flumioxazin.

    7.  It is possible to substitute tillage for burndown herbicides.  Make sure that the tillage is deep and thorough enough to completely uproot weeds.  Weeds that regrow after being “beat up” by tillage are often impossible to control for the rest of the season.  Tillage tools that do not uniformly till the upper few inches (e.g. TurboTill) should not be used for this purpose.

    8.  Late burndown in corn is typically a less dire situation compared with soybeans.  Reasons for this include: 1) the activity of some residual corn herbicides such as atrazine and mesotrione on emerged weeds – mesotrione has apparently become pretty cheap, and adding a few ounces to an atrazine premix can improve burndown substantially; 2), the ability to use dicamba around the time of planting; 3) the tolerance of emerged corn to 2,4-D and dicamba, and 4) the overall effectiveness of available POST corn herbicides.  Overall, while not adequately controlling emerged weeds prior to soybean planting can make for a tough season, there is just more application flexibility and herbicide choice for corn.  Having said this, be sure to make adjustments as necessary in rate or herbicide selection in no-till corn fields.

  3. Soybean Planting Date, Seeding Rate, and Row Width

    Author(s): Laura Lindsey

    Before heading out to the field this spring, download a free pdf of the recently revised Ohio Agronomy Guide available here: https://stepupsoy.osu.edu/soybean-production/ohio-agronomy-guide-15th-edition Also, check out other information related to soybean management at http://stepupsoy.osu.edu.

    Planting date. Planting date strongly influences soybean yield. In 2013 and 2014, we conducted a planting date trial at the Western Agricultural Research Station near South Charleston, Ohio.  In both years, soybean yield decreased by 0.6 bu/ac per day when planting after mid-May. The greatest benefit of planting May 1 to mid-May is canopy closure which increases light interception, improves weed control by shading out weeds, and helps retain soil moisture. 

    However, planting too early (before field conditions are adequate) comes with a risk.  Factors such as damping-off and pressure from bean leaf beetle are concerns to keep in mind, as well as the possibility of a late spring frost.  (Our early May planting date in northeastern Ohio in 2013 was damaged by bean leaf beetle and two frosts that occurred mid-May.)

    Before heading to the field, consider the conditions you will be planting into. Soybean germination begins when soil temperatures reach 50°F and moisture is present at the planting depth of 1-1.5 inches. Do not plant early if the soil is excessively cold or wet. Slower germination and compaction can negate the benefits of the earlier planting date. Timely planting is critical for maximizing yield in soybeans, but using good judgement on field conditions plays a role that is equally important to determining yield potential.

    Seeding rate. When soybeans are planted in May, a final (harvest) population of 100,000 to 120,000 plants per acre is generally adequate for maximum yield. Final soybean population depends on germination, emergence, disease and insect pressure, competition from other plants, etc. In most situations, 140,000 seeds per acre should result in at least 100,000 plants per acre at harvest. 

    Row spacing.  In Ohio, most soybeans are planted in row widths ≤ 15 inches.  Soybeans grown in narrow rows (≤ 15 inches) tend to out-yield soybean produced in wide row width (30 inches) due to increased sunlight interception in narrow rows. Row width should be narrow enough for the soybean canopy to completely cover the interrow space by the time the soybeans begin to flower.

    In our 2016 row width study, soybeans grown in 7.5 and 15-inch rows yielded similarly while soybeans grown in 30-inch rows yielded on average 15-20% lower. Our trial located at the Western Agricultural Research Station in Clark County was planted the end of May (pictured below). In June, the soybeans planted in 30-inch rows looked better than the soybeans planted in 15 and 7.5-inch row widths. However, the soybeans planted in 30-inch rows did not achieve canopy closure until after July 15. The 30-inch plot pictured below yielded 59 bu/acre while the 15 and 7.5-inch plots pictured below yielded 81 and 85 bu/acre, respectively. 


  4. Soil Temperatures and Accumulated GDD

    The slow start to 2018 planting continues, but we would expect progress to accelerate this week as rainfall amounts lessen and air temperatures increase. We are at the calendar date where ground conditions rather than concerns about soil temperature will dictate planting. Soil temperature and accumulated Growing Degrees Days (GDD) from select OARDC Weather Station locations will be provided for at least a couple more weeks to help gauge when crop emergence should be seen. Based on current accumulated GDD (Table 1) we would not expect any emerged corn yet, based on the April 12 planting window that occurred, but any corn planted in that window in Southern Ohio should emerge soon.



    Table 1. Weekly and Accumulated GDD values since April 12 from select OARDC weather locations. Corn emergence typically occurs between 100 and 120 GDD accumulation.


    OARDC Branch Location






    North Central-Fremont

    April 12-15






    April 16-22






    April 23-29






    Sum of GDD Since April 12






  5. 2018 Small Grains Field Day


    Plan now to attend the 2018 Small Grains Field Day on June 12.  The event will begin with registration and sign in at 9:30 am at the OARC Schaffter farm located at 3240 Oil City Road, Wooster OH.  The cost is $25 per person when registered by June 4. Beginning June 5, registration will be $35 per person. Lunch is included in the registration fee. Commercial and private pesticide applicator credits as well as Certified Crop Advisor (CCA) credits are available to field day participants.  To register on-line, visit https://go.osu.edu/2018SmallGrains.

    After some brief introductory comments at 10:00 am, shuttles will take participants to field plots.  Morning topics include:

    • Use of small grains in a soybean production system which will include planting demonstrations into small grain cover crops along with a discussion of insect and slug management
    • Malting barley research which will include selecting varieties adapted to Ohio conditions along with agronomic considerations
    • Malting barley economics which will include a discussion on demand for malting barley, grower contracts, and malting barley enterprise budget
    • Small grain agronomics, which will include a discussion on malting barley disease management and recent work with wheat fertilizer trials to manage wheat fertility.

    After lunch served in the Schaffter Farm shop, participants will choose between one of two afternoon sessions.  Session A will focus on wheat variety development, current wheat breeding work, identification of wheat diseases and management of wheat diseases.  This session will take place at the OARDC Snyder farm.  Shuttles are provided for transportation to and from the farm plots.  Session B is a tour of the USDA Soft Wheat Quality Lab located on the OARDC campus.  In addition to the tour of the facilities, participants will hear about current research and see demonstrations regarding wheat quality evaluation.

    The Small Grains Field Day will conclude around 3:00 pm.  Sponsors of the 2018 Small Grains Field Day include Ohio Certified Seed, Ohio Soybean Council and the Ohio Corn and Wheat Board. 

    For more information about the field day, including an event flyer, go to http://go.osu.edu/agwayne and click on the “Small Grains Field Day” heading or contact the Wayne County Extension office by phone at 330-264-8722.

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.


Aaron Wilson (Byrd Polar & Climate Research Center)
Amanda Douridas (Educator, Agriculture and Natural Resources)
Andy Michel (State Specialist, Entomology)
Anne Dorrance (State Specialist, Soybean Diseases)
Beth Scheckelhoff (Educator, Agriculture and Natural Resources)
Bruce Clevenger, CCA (Educator, Agriculture and Natural Resources)
Chris Zoller (Educator, Agriculture and Natural Resources)
Dean Kreager (Educator, Agriculture and Natural Resources)
Dennis Riethman (Educator, Agriculture and Natural Resources)
Elizabeth Hawkins (Field Specialist, Agronomic Systems)
Garth Ruff (Educator, Agriculture and Natural Resources)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Greg LaBarge, CPAg/CCA (Field Specialist, Agronomic Systems)
Harold Watters, CPAg/CCA (Field Specialist, Agronomic Systems)
Jeff Stachler (Educator, Agriculture and Natural Resources)
Kelley Tilmon (State Specialist, Field Crop Entomology)
Laura Lindsey (State Specialist, Soybean and Small Grains)
Lee Beers, CCA (Educator, Agriculture and Natural Resources)
Les Ober, CCA (Educator, Agriculture and Natural Resources)
Mark Badertscher (Educator, Agriculture and Natural Resources)
Mary Griffith (Educator, Agriculture and Natural Resources)
Mike Gastier, CCA (Educator, Agriculture and Natural Resources)
Peter Thomison (State Specialist, Corn Production)
Pierce Paul (State Specialist, Corn and Wheat Diseases)
Sam Custer (Educator, Agriculture and Natural Resources)
Sarah Noggle (Educator, Agriculture and Natural Resources)
Steve Culman (State Specialist, Soil Fertility)
Wayne Dellinger (Educator, Agriculture and Natural Resources)


The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For more information, visit cfaesdiversity.osu.edu. For an accessible format of this publication, visit cfaes.osu.edu/accessibility.