Corn Newsletter : 2018-21

  1. Only Susceptible Varieties are Prone to Diseases and May Require a Fungicide Application

    Author(s): Anne Dorrance

    From the scouting reports from the county educators and crop consultants – most of the soybeans in the state are very healthy with no disease symptoms.  However, as the news reports have indicated, there are a few varieties in a few locations that have higher incidence of frogeye leaf spot than we are accustomed to seeing at this growth stage – mid R2 – flowering in Ohio.  Most of the reports to date are along and south of route 70, which based on the past 12 years is where frogeye is the most common.  When this disease occurs this early in the season, where it can be readily observed, this is a big problem and should be addressed right away with a fungicide soon and a second application at 14-21 days later depending on if disease continues to develop and if environmental conditions (cool nights, fogs, heavy dews, rains) continue.  Table 1. Lists the fungicides that have very good activity towards frogeye leaf spot based on University trials around the country (thank you land grant university soybean pathologists in NCERA-137). Note that on this list there are no solo strobilurin fungicides, as we have detected strains of the fungus, Cercospora sojina, that are resistant to this class of fungicides in the state.

    What if there is no frogeye on the varieties in your area – then wait and keep scouting.  If you know your seed companies resistance rating scale and your variety has good resistance, then you just saved a lot of money by not having to spray a fungicide.

    We know from previous work that if frogeye does not appear in a field until growth stage R5 – on a susceptible variety - there is no yield loss.  This is most common in the northern part of Ohio (route 30 & north), it’s rare to have a fungicide pay for frogeye leaf spot.  This disease does not really begin to move until later in the season.

    This disease is fairly easy to scout for.  The newer leaves are the ones that are susceptible not the older, fully expanded leaves.  So take a look before you buy.  Check your variety ratings and keep listening to where it has been detected in your area. More importantly, we do need to evaluate if any of the strains of C. sojina are susceptible to frogeye leaf spot in the state, so please send us leaves with lesions.

    Identification of Frogeye Leaf Spot

    Fungicides for Frogeye Leaf Spot

  2. Controlling Marestail in Double-Crop Soybeans

    Marestail (Horseweed)
    Author(s): Mark Loux

    A uniform wheat crop can provide effective suppression of marestail, especially when combined with some in-crop herbicides.  It is nonetheless typical for marestail plants to be evident after the wheat is harvested, and these should be controlled prior to double crop soybean emergence.  There can be a couple types of marestail plants to deal with in this situation:  1) small ones that were lurking near the base of the wheat plants, which are largely not disturbed by the combine; and 2) larger ones that may have been present in areas of thin wheat stand, which get cut off by the combine and then regrow.  The first of these is really the more ideal situation because the small undisturbed plants can usually be controlled by one of the following:   glyphosate plus Sharpen + MSO; glufosinate (Liberty, Interline, Cheetah, etc); or possibly even Gramoxone plus metribuzin (although this is more effective when mixed with 2,4-D).  Adding metribuzin to any of these can improve control of emerged marestail and provide some residual control of later emerging marestail as well.  

    The second situation, where marestail plants regrow following damage by the combine, is more challenging.  We have tried a number of treatments at multiple locations where marestail have been in this condition, and have not been able to obtain more than about 80% control.  This level of control can prevent competition with the soybeans and minimize seed production.  Best options for this situation, ranked from most to least effective: 

    Glufosinate + Sharpen + metribuzin + MSO

    Glufosinate  + Sharpen + MSO

    Glyphosate + Sharpen + metribuzin + MSO

    Glyphosate + Sharpen + MSO

    A few other things to consider:

    - Glyphosate treatments may be the better choice where large grasses are present, or where grasses other than giant foxtail are present.

    - All of these treatments contain one or more contact herbicides (not systemic) and should be applied in at least 15 gpa with the appropriate nozzle and adjuvants to ensure thorough coverage. 

    - Planting LibertyLink soybeans provides more flexibility in when glufosinate can be applied, and also provides for the postemergence use of glufosinate.  We do not advise waiting too long after soybean planting to apply the glufosinate though – the marestail won’t get any easier to control.  In Roundup Ready or non-GMO soybeans, there will be no postemergence option that is effective on marestail.

    - The preemergence burndown is responsible for much of the weed control in double crop soybeans, and we advise against trying to go too simple or inexpensive.  Adding some residual herbicide is not necessarily a bad thing in double crop, but it is not near as important compared with full-season soybeans.  And some residual soybean herbicides should not be applied this late in the season where corn will be planted next year due to carryover concerns.  Any of the products containing chlorimuron, cloransulam, imazaquin, or imazethapyr should generally not be applied this late.

    - Much of the information here also applies to control of marestail in wheat stubble, in the absence of soybeans.  However, 2,4-D can be used in wheat stubble, and also dicamba if the temperatures are cool enough.  Our research in wheat stubble has shown that applying before the end of July is more effective, and even glyphosate/2,4-D can prevent most of the seed production if applied by then.  Preventing marestail seed production is the goal in wheat stubble.  The marestail plants present in July following wheat harvest will not survive through the winter, and any chemical or nonchemical approach that prevents them from flowering and producing seed is adequate.

  3. Western Bean Cutworm Montoring

    Western bean cutworm adult

    Monitoring for WBC adults continues across Ohio with trap counts slowly increasing for July 1 through 7. Last week, 21 counties monitored 61 traps (Figure 1). Overall across all locations, there was an average of 3.4 moths per trap (217 captured).  This is an increase from an average of 1.2 moths/trap the previous week.  The general trend of WBC trap catches appears to be similar to 2016 where peak flight was the third week in July; however, average trap numbers are currently lower than 2016 (Figure 2). Western bean cutworm adults can peak during any week in July depending on the year.

    Figure 1. Average Western bean cutworm adult per trap in Ohio counties, followed in parentheses by total number of traps monitored in each county for the week ending July 7, 2018. Legend in the bottom left describes the color coding on map for the average WBC per county.


    Figure 2. Average Western bean cutworm (WBC) trap counts for 2016 (blue), 2017 (red) and 2018 (green).


  4. 4R Technology Review Field Day in July 17, 2018

    Registration is currently underway for the 2018 4R Technology Review Field Day, hosted by the Ohio AgriBusiness Association, and featuring presentations by various OSU and USDA-ARS staff. This event will take place Tuesday, July 17, on one of the Blanchard River Demonstration Farms. Registration is free and includes a complimentary lunch. Sign-in begins at 8:30 AM, the event at 9:00 and will conclude around 4:00 PM.

    • The program this year will be on the Kellogg Farm in Hardin County located at 17392 TR 50, Forest, Ohio 45843.
    • A panel of Blanchard River Demonstration Network farmers will speak about their experiences – in the watershed and with nutrient management.
    • Afternoon sessions include field demonstrations featuring fertilizer application equipment from ETS’ Soil Warrior, New Leader, Harvest International and John Deere..  
    • This is an excellent opportunity to gain valuable information about nutrient management and water quality issues.
    • Available will be CCA continuing education credits.
    • A full agenda is viewable at

    For more details and to register, please visit the OABA event page:  The registration deadline for this event is Friday, July 13, so don’t miss out!

  5. Time to Register to Attend the 2018 Manure Science Review

    Soil Health Demonstration
    Author(s): Mark Badertscher

    Have you registered to attend this year’s Manure Science Review?  July 16 is the last day to register at the reduced rate of $25.  Livestock producers, manure applicators and others will want to make sure they visit to register for the upcoming field day being held near Forest in Hardin County on July 25.  Registration is $30 per person if completed after July 16.  Breakfast (coffee and donuts) and lunch is included with the registration fee.

    The 2018 Ohio State University Manure Science Review will take place at the Watkins farm located at 18361 Township Road 90, Forest, OH 45843.  The program will begin at 8:45 am, while registration, coffee and donuts will be offered in the morning starting at 8:15 am before the field day kicks off with the afternoon activities ending by 3:30 pm.

    The morning educational sessions in the main tent will focus on Waterhemp and Other Weed Seeds in Manure, Avoiding Manure Spills, Manure Application: Rules and Liability, Reducing Phosphorus Runoff, Regulations Update, and Valuing Manure.  There will be indoor demonstrations of Rainwater/Runoff Simulation and Cover Crops, OnMRK nutrient record keeping app, Ohio Farm Bureau Federation Demonstration Farms, and exhibitor introductions with displays.

    Following lunch, afternoon field demonstrations will include Preferential flow, Manure spreader calibration, Soil health: #SoilYourUndies, Shallow tillage for manure application, Seeding cover crops with a converted Highboy, Side dressing corn with manure, Center pivot irrigation, and Mortality composting.  For more information about this year’s Manure Science Review, go to

Upcoming Events

About the C.O.R.N. Newsletter

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)
Anne Dorrance (State Specialist, Soybean Diseases)
Bruce Clevenger, CCA (Defiance County)
Clifton Martin, CCA (Muskingum County)
David Dugan (Adams County)
Dennis Riethman (Mercer County)
Elizabeth Hawkins (Field Specialist, Agronomic Systems)
Erika Lyon, CCA (Jefferson and Harrison Counties)
Garth Ruff (Henry County)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Greg LaBarge, CPAg/CCA (Field Specialist, Agronomic Systems)
Harold Watters, CPAg/CCA (Field Specialist, Agronomic Systems)
Jason Hartschuh, CCA (Crawford County)
Jeff Stachler (Auglaize County)
John Schoenhals, CCA (Williams County)
Kelley Tilmon (State Specialist, Field Crop Entomology)
Lee Beers, CCA (Trumbull County )
Les Ober, CCA (Geauga County)
Mark Badertscher (Hardin County)
Mark Loux (State Specialist, Weed Science)
Mike Gastier, CCA (Huron County)
Pierce Paul (State Specialist, Corn and Wheat Diseases)
Rory Lewandowski, CCA (Wayne County)
Sam Custer (Darke County)
Sarah Noggle (Paulding County)
Trevor Corboy (Greene County)


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 For an accessible format of this publication, visit