Corn Newsletter : 2016-10

  1. Armyworm and Cover Crops

    Armyworm in Corn Whorl

    True armyworm (Pseudaletia unipuncta) overwinters in the southern U.S. and adult moths migrate northward in April and May.  Females lay eggs in grassy fields including rye cover crops, and the young caterpillars feed there, typically attacking corn from early may through June.  Corn planted into rye cover is at greater risk for early season armyworm feeding because the caterpillars may already be in the field and move to the corn after the rye is killed.  Armyworm can also move into corn from other fields such as wheat, in which case infestation usually occurs along field edges. Though some growers include an insecticide in their rye burndown herbicide, this prophylactic application is not recommended because in many years the armyworm populations will not be sufficient to warrant it or its cost.  Foliar insecticides work well as a rescue treatment and can be applied in years when scouting indicates it will help.  Corn fields planted into rye cover or into other no-till grassy habitats should be scouted beginning in early to mid May in southern Ohio and mid to late May moving further north.

    Armyworms take shelter during the day in corn whorls or under debris so it can be difficult to find them.  Their feeding damage is more obvious, with ragged edges that progress towards the midrib.  When 15 to 20% of the stand has feeding damage the field should be re-checked within a few days to determine if defoliation is increasing.  Rescue treatments in corn may be needed if stand infestation is greater than 50% and larvae are not yet mature. If defoliation remains less than 50% and the new growth shows minimal feeding injury, the stand will likely recover with minimal impact on yield.  Early scouting is important because the caterpillars are easier to kill when small, and also because larvae nearing maturity have already done most of their feeding.  

    A number of labeled insecticides are available for armyworm (, and certain Bt trait packages are also labeled for true armyworm control (



    Pseudaletia unipuncta
    Photo credit: James Kalisch, University of Nebraska,

  2. Adjusting No-till Burndown Programs for Later Planting

    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.  There have been opportunities to apply burndown herbicides in much of the state over the past several weeks, and some areas have made considerable progress on planting.  Other areas have made little progress.  We are probably not in a true “late planting situation” yet, but some of the state is now wet and not that warm, and more rain coming midweek.  

    The longer-range forecast calls for drier than normal conditions and higher than normal temperatures apparently.   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.   In our research plots, we appear to have as good a winter annual population as we have ever had, possibly due to a relatively mild winter (weed scientists admittedly probably have more appreciation for a “good” weed population than the rest of the world).   There is a substantial difference in weediness between the fields treated with herbicides last fall versus the lack of a fall treatment.  Among other benefits, the fall treatment provides a clean start in the spring that persists for a while and ‘buys time’ in a delayed planting situation. 

    Marestail is one of the bigger concerns in a late burndown situation, especially when not initially 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).  Marestail in fields not treated last fall has reached the 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.  The addition of metribuzin can also result in more consistently effective marestail control.  And a reminder - 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.  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.  Consider substituting Gramoxone or glufosinate for glyphosate?  Gramoxone is   less effective than glufosinate on marestail, but glufosinate can struggle some in a dense, large no-till burndown situation.  Either one should 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.

    5.  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.

    6.  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.

    7.  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 (e.g. atrazine, mesotrione) on emerged weeds; 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. Wheat Diseases: Updated Facts and Pictures_Part 1

    Septoria tritici blotch: This is usually one of the various diseases to show up during the wheat seasons. It develops best under cool, wet conditions, with symptoms commonly detected on lower leaves. Initial lesions appear as yellowish or chlorotic flecks that later enlarge into irregular, brown-to-reddish brown lesions. As the lesions age, the centers become bleached with gray or ash-white centers, with small, dark-brown to black specks. The presence of these specks, called pycnidia, is the most reliable characteristic to help tell this disease apart from other disease such as Stagonospora leaf blotch and tan spot that typically develop later in the season. Read more about Septoria and other leaf blotch diseases of wheat at:

    Powdery mildew: This is another disease that usually shows up early in the season. Wheat plants are most susceptible during periods of rapid growth, especially between the stem elongation and heading growth stages. As a result, mildew is most prevalent on the lower leaves of susceptible varieties in late April or early May, especially when the wheat stand is dense (heavy tillering) due to high nitrogen application and seeding rates. Powdery mildew is one of the easiest foliar diseases to identify since it is the only disease that produces powdery, fluffy, white-to-gray fungal growth on leaves, and eventually on stems and even heads. Read more about wheat powdery mildew at:

    Leaf RustLeaf Rust: Unlike powdery mildew and Septoria tritici blotch, leaf rust typically develops toward the latter half of the wheat season. This is mainly because the fungus that causes this disease does not usually survive in Ohio, and as such, spores have to be blown up from the south. However, under mild winter conditions similar to those we experienced this past winter, the fungus survives on volunteer plants and may infect the crop just as early as powdery mildew and Septoria. Leaf rust is the most common of three rust diseases that affects wheat, and can be identified by the presence of rusty-colored pustules erupting through the leaf surface. It can be distinguished from other leaf diseases by rubbing the leaves and looking for the rusty color on your finger.  Read more about rust diseases of wheat at:

    Septoria, powdery mildew, and leaf rust are all capable of substantially reducing wheat yield and test weight, especially if your cultivar is susceptible and the flag leaf is damaged between Feekes 8 and Feekes 10.5, before grain fill is complete. Scout fields and look for these diseases and use this information to help you make your fungicide application decision. This would be a good time to apply a fungicide to protect the flag leaf if your cultivar is susceptible. There are several fungicides to choose from, select one that is effective against all three diseases. Read more about wheat fungicides at:

  4. CHOICE - The Big Data Confusion: Part 7

    Choice as it relates to the discussion of data services and tools is critically important to growers today.  As a grower, you should have a choice on who to share your data with and the selection of service(s) to utilize with Agriculture Technology Providers (ATPs). According to the Privacy and Security Principles for Farm Data published by the American Farm Bureau directly states, ATPs should explain the effects and abilities of a farmer’s decision to opt in, opt out or disable the availability of services and features offered by the ATP. If multiple options are offered, farmers should be able to choose some, all, or none of the options offered. ATPs should provide farmers with a clear understanding of what services and features may or may not be enabled when they make certain choices.”

    Quite simply, growers should understand options provided by ATPs and the choices provided.  An important choice to understand is whether you can “opt in” and “out of” a service and if you choose to opt out, can the ATP provide a copy of your data?   It is also important to select an ATP that clearly explains a grower’s choice to opt in, opt out, or disable any services offered and if one opts out, what are the terms.  Sometimes, multiple options are offered and trusted ATPs will ensure that all options are disclosed and clearly explained within the contract agreements.  This allows the grower to make an educated decision about what services they are receiving or utilizing.  Growers should even be given a choice as to what services are enabled for them.  Remember, choices related to data services and tools are important to a grower’s decisions and business around data.

  5. Damp Conditions this Week

    Author(s): Jim Noel
    After a wet week last week with anywhere from 0.50 to 2.00 inches in most places there weather will relax some this week. However with cooler temperatures evaporation will be down so even light rains will keep things on the damp side this week.
    April ended with temperatures ranging from 1-2F below normal in northern Ohio and 0-1F above normal in southern Ohio or near normal for the state average. This followed a very warm March with temperatures 5-10F above normal.
    April rainfall ranged generally +/- 1 inch from normal.
    The outlook for May calls for slightly warmer and drier than normal conditions in most area. The following is a weekly breakdown...

    May 3-8                  Outlook                   Traffic Light
    Temperatures          -1 to -3F                  YELLOW due to cool conditions
    Hard Freeze            None                       GREEN
    Frost                      None or patchy         GREEN
    Wind > 30 mph       Little or None            GREEN
    Rainfall                   <1 inches                 GREEN-YELLOW
    Evaporation             Limited                    YELLOW-RED

    May 9-16                 Outlook                   Traffic Light
    Temperatures          +/- 1F                      GREEN
    Rainfall                   <1 inches                 GREEN-YELLOW
    Evaporation             NORMAL                 GREEN-YELLOW

    May 16-23              Outlook                   Traffic Light
    Temperatures          +4-8F                      GREEN
    Rainfall                   <1 inches                GREEN
    Evaporation             ABOVE                   GREEN

    May 23-30              Outlook                   Traffic Light
    Temperatures          +2-4F                       GREEN
    Rainfall                   <1 inches                 GREEN
    Evaporation             ABOVE                    GREEN

    You can monitor all this at the NOAA/NWS/OHRFC link at and
    The latest two week rainfall total is near 2 inches as seen in the NOAA/NWS/OHRFC rainfall outlook graphics. The one area that could have elevated rain areas in the state of Ohio in the first half of May will be near Lake Erie and the boundary between land and lake will influence the pattern.
  6. June 1: On-Farm Wheat Field Day in Pickaway County

    On June 1, we will be having an on-farm wheat field day in Pickaway County near Circleville at the site of our Ohio Wheat Performance Test and other agronomic wheat trials. Click here for more information.

    Registration is free, but we are requesting registration by Friday, May 20 for lunch count. Lunch will be held at Jackson Township Hall. Please register through the Pickaway County Extension office (740-474-7534 or   

    Topics include:

    How low can you go? Wheat freeze tolerance
    Minimum wheat stand to maximize profits
    Soil fertility considerations for improved efficiency
    Wheat disease identification and management
    Ohio Wheat Performance Test

    Featured speakers include:

    OSU’s Wheat Agronomy Team: Laura Lindsey, Matt Hankinson, Doug Alt, and Allen Goodwin
    OSU Plant Pathologist: Pierce Paul
    Pickaway County Extension: Mike Estadt
    Michigan State University Soil Fertility Specialist: Kurt Steinke

    Field day is sponsored by the Ohio Small Grains Marketing Program and Keynes Bros. Milling.

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.


Alan Sundermeier, CCA (Wood County)
Amanda Bennett (Miami County)
Bruce Clevenger, CCA (Defiance County)
David Dugan (Adams County)
Debbie Brown, CCA (Shelby County)
Dennis Riethman (Mercer County)
Ed Lentz, CCA (Hancock County)
Eric Richer, CCA (Fulton 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)
Lee Beers, CCA (Trumbull County )
Les Ober, CCA (Geauga County)
Mark Badertscher (Hardin County)
Mike Gastier, CCA (Huron County)
Nathan Douridas, CCA (Farm Science Review Farm Manager)
Peter Thomison (State Specialist, Corn Production)
Rory Lewandowski, CCA (Wayne County)
Sam Custer (Darke County)
Sarah Noggle (Paulding County)
Steve Culman (State Specialist, Soil Fertility)
Ted Wiseman (Perry County)
Wayne Dellinger (Union 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.

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