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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter: 2015-08

  1. Burndown of Cover Crops

    Author(s): Mark Loux

    It can be difficult to find a comprehensive source of recommendations for the control of all of the possible cover crops prior to planting.  Some resources we have used recently:

    “Successful termination of cover crops”, Purdue Extension, Pub #WS-50-W, available free online.

    “A weed scientist’s perspective on cover crops”, a Powerpoint pdf by Kevin Bradley, University of Missouri Weed Science, available free online.  Contains a summary of his research on cover crop termination and effect of residual herbicides on cover crop establishment.

    Information we have gleaned on cover crop burndown based on these and various other resources:

    - optimal management of cover crops in the spring comes with experience and varies with  soil type, weather, etc.  Check with other growers/agronomists/consultants who have worked with cover crops in your area of the state since they may have the best knowledge for your situation.

    - In general, smaller is better when trying to kill cover crops but applying too early can be detrimental under certain soil moisture conditions.

    - Radish and oats typically die on their own over the winter and do not require additional burndown.  However, radish that does survive the winter can be difficult to control.

    - cereal rye, winter pea, and hairy vetch are relatively easy to kill, while wheat, crimson clover, and annual ryegrass can be difficult to kill.

    - Overall, glyphosate is still the most effective herbicide for cover crop control.  It does not usually need help to control grasses.  Rates should be increased for control of certain grasses, such as annual ryegrass and wheat.  Mixing with other herbicides can reduce control of these species, especially under cold conditions.  Glyphosate should usually be mixed with a growth regulator (2,4-D, dicamba, clopyralid) for control of legumes and other broadleaf covers.

    - Gramoxone can be effective on hairy vetch and cereal rye (bigger is better), and even on small annual ryegrass.  Most effective when mixed with atrazine, metribuzin, and/or 2,4-D.

    - Liberty is expensive and not usually a good choice for control of covers.  Most effective when applied with atrazine during warm, sunny weather.

    - In many cases, the POST application of glyphosate in Roundup Ready corn or soybeans will help control covers that the burndown is not completely effective on.

    More specifics for a few species:

    Cereal rye: up to 18 inches tall, glyphosate (0.75 lb ae/A).  Increase rate on taller rye.  Antagonism with other herbicides only a minor concern.  Gramoxone can be effective on taller plants at high rates, especially when applied with atrazine and 28%.  Adequate spray coverage is essential with Gramoxone – at least 20 gpa.

    Winter wheat: up to 18 inches tall, glyphosate at 1.1 to 1.5 lb ae/A.  Increase rate on taller wheat.  Antagonism with residual herbicides and 28% is a concern – apply alone in water for most consistently effective control.  Smaller is better.  Gramoxone is not consistently effective.

    Annual ryegrass: glyphosate, minimum of 1.5 lbs ae/A.  Increase rate on larger plants or in cold weather.

    Hairy vetch and winter pea: glyphosate (0.75 to 1.1 lb ae/A) plus 2,4-D or dicamba.  Gramoxone can control larger hairy vetch – apply with atrazine and/or 2,4-D.

    Alfalfa, clover: Glyphosate (1.1 to 1.5 lb ae/A) plus 2,4-D, dicamba, or clopyralid.  Clopyralid is very effective on these species.

  2. Wheat Management by Growth Stage

    The winter wheat crop is greening up and as such growers will need to pay attention to crop growth stage in order to make adequate management decisions. Wheat growth stage identification is critical for effective timing of fungicide, insecticide, herbicide, and fertilizer applications. Hence, crop growth staging is extremely important, since failure to correctly identify these stages may lead to inadequate timing of applications, which may result in violation of pesticide label restrictions (products being applied off label), inferior efficacy or product performance, and injury to the crop. In addition, effective and timely pesticide applications and pest and disease management are extremely important for profitable wheat production as they all affect the number of tillers/heads produced per acre, seeds produced per head, and seed size. These all add up to higher grain yields and excellent test weights.

    If you have not done so already (and you probably haven’t due to the excessive rainfall…), now is the time to check fields in order to identify crop growth stage. Currently, most of the wheat in Ohio is between the green-up and erect stem stages (Feekes 2-5) of development and will likely begin jointing (Feekes 6) within the next 7-10 days as the weather continues to warm up.

    Feekes Growth Stage 2-5 (tillering, green-up and erect growth). Tillering (the production of side shoots) usually occurs in the fall and early spring. For most of the early planted fields, particularly those in the southern half of the state, tillering is now complete (Feekes 3) and the wheat is either at or approaching the erect stem stage (Feekes 4) of development. This is the ideal stage for evaluating your wheat stand, begin scouting for insects and weeds, top-dressing nitrogen, and finishing-up herbicide application. For those late-planted or northern fields that are still greening-up (not yet at the Feekes 3 growth stage), a nitrogen application at this time will likely increase tillering, and consequently, the number of head produced per foot of row. However, for those fields at the Feekes 4-5 growth stage, nitrogen application will have very little effect on tiller development but will affect the number of seeds produced per head and seed size. To read more about evaluating wheat stands see this C.O.R.N. newsletter article from a couple of weeks ago:

    Feekes Growth Stage 6 (first node visible). This growth stage can be identified by examining the large tillers in the fields for the presence of the first node. Pull multiple large tillers, strip down the lower leaves and leaf sheaths on the stem, and check for the presence of the first node at the base of the stem. If this node is visible (or can be felt), your wheat is at jointing (growth stage 6). At growth stage 6, the node is above the soil line and appears as a slightly swollen area of a slightly different shade of green from the rest of the stem. If the node is not yet visible, the wheat is probably at Feekes growthstage 5. Feekes growth stage 6 usually occurs mid- to late April.

    Growth stage 6 signals the beginning of stem elongation. Nitrogen should be applied by this time to maximize yield. This is also the growth stage when some herbicides can no longer be applied. For instance, herbicides such as 2,4-D, Banvel, or MCPA should not be applied after Feekes growth stage 6.0, as these materials can be translocated into the developing spike, causing sterility or distortion. Huskie and products containing tribenuron and thifensulfuron can be applied through Feekes stage 8, and bromoxynil can be applied until stage 9. Keep in mind that the tribenuron/thifensulfuron-containing products such as Harmony Xtra should generally be mixed with dicamba, 2,4-D or MCPA to broaden the spectrum of control, which affects how late they can be applied. The chart on page 143 of the 2015 Weed Control Guide provides a snapshot of growth stage information. For more on wheat growth stage identification visit:

    You should also begin scouting for early season diseases such as Septoria and powdery mildew. However, we do not recommend foliar fungicide application this early in the season. Although some producers may be interested in tank-mixing foliar fungicides with nitrogen or herbicides, our data shows that under conditions in Ohio fungicide applications at or before jointing do not provide adequate protection of the flag leaf and the heads.

    Keep reading the C.O.R.N. newsletter for more updates on the progress of the wheat crop and management tips and guidelines.  

  3. Getting Your Corn Crop Off to a Good Start in 2015

    Author(s): Peter Thomison

    Mistakes made during crop establishment are usually irreversible, and can put a "ceiling" on a crop's yield potential before the plants have even emerged. The following are some proven practices that will help get a corn crop off to a good start.

    Perform Tillage Operations Only When Necessary and Under the Proper Soil Conditions: Avoid working wet soil and reduce secondary tillage passes. Perform secondary tillage operations only when necessary to prepare an adequate seedbed. Shallow compaction created by excessive secondary tillage can reduce crop yields. Deep tillage should only be used when a compacted zone has been identified and soil is relatively dry. Late summer and fall are the best times of year for deep tillage.

    Complete Planting by Early May: The recommended time for planting corn in northern Ohio is April 15 to May 10 and in southern Ohio, April 10 to May 10. However if soil conditions are dry and soil temperatures are rising fast, start planting before the optimum date. During the two to three weeks of optimal corn planting time, there is, on average, only one out of three days when field work can occur. Avoid early planting on poorly drained soils or those prone to ponding. Yield reductions resulting from "mudding the seed in" are often much greater than those resulting from a slight planting delay. If the rainy conditions we are currently experiencing persist, remember that good yields are still possible with later planting dates. In 2011 and 2012, later planted corn in some parts of Ohio yielded better than early corn due to unusually favorable rainfall and temperature conditions in late July and August.

    Adjust Seeding Depth According to Soil Conditions: Plant between 1-1/2 to 2 inches deep to provide for frost protection and adequate root development. Seeding depth should be monitored regularly during the planting operation and adjusted for varying weather and soil conditions. Irregular, especially shallow planting depths contribute to uneven plant emergence, which can reduce yields.

    Adjust Seeding Rates on a Field-by-Field Basis: Lower seeding rates are usually preferable when droughty or marginal soils limit yield potential. On soils averaging about 120 bu/acre or less, final stands of 20,000 to 22,000 plants/acre are usually adequate for optimal yields. Plant population studies conducted by OSU from 2006 to the present suggest that on more highly productive soils, with greater yield potential, final stands of 30,000 plants/acre or higher were required to maximize yields. Most research suggests that planting a hybrid at suboptimal seeding rates is more likely to cause yield loss than planting above recommended rates (unless stalk lodging becomes more severe at higher population levels) and harvest delays occur. When early planting is likely to create stressful conditions for corn during emergence, e.g. no-till in corn residues in early to mid April, consider seeding rates 10 to15% higher than the desired harvest population. Follow seed company recommendations with regard to optimal seeding rates for different hybrids.

    Plant a Mix of Hybrid Maturities: Planting a mix of hybrids with different maturities reduces damage from diseases and environmental stress at different growth stages (improving the odds of successful pollination) and spreads out harvest time and workload. Consider spreading hybrid maturity selections between early, mid, and full season hybrids for example, a 25 50 25 maturity planting, with 25 percent in early to mid season, 50 percent in mid to full season, and 25 percent in full season. Planting a range of hybrid maturities is probably the simplest and most effective way to diversify and broaden hybrid genetic backgrounds.

    Plant full season hybrids first: Planting a full season hybrid first, then alternately planting early season and mid season hybrids, allows the grower to take full advantage of maturity ranges and gives the late season hybrids the benefit of maximum heat unit accumulation. Full season hybrids generally show greater yield reduction when planting is delayed compared with short to mid season hybrids.

  4. Managing Marestail This Spring – The Perfect Storm?

    Author(s): Mark Loux

    This spring is shaping up to be one where marestail control problems abound, based on the following:

    a) not many fields were treated with herbicide last fall due to wet weather and the late harvest.  Fall treatment results in a field free of overwintered marestail in spring, which takes the pressure off spring burndown treatments – they just have to control the newly emerging small marestail.  One strategy to compensate for lack of fall treatment is to apply herbicide early in spring when overwintered marestail plants are still small, but….

    b) wet weather so far this spring has largely prevented application of burndown herbicides, and this looks to be the case through sometime next week based on the forecast (not sure this applies to the entire state but much of it for sure), which means that…...

    c) when we can finally apply spring burndown treatments, they have to be comprehensive enough to control fairly old, overwintered marestail.  We know that the standard-rate glyphosate/2,4-D burndown can struggle in this situation, so some modification/replacement of this may be warranted.  Some possible modifications to consider:

    - increase the 2,4-D rate from 0.5 to 1.0 lb ai/A, which can improve control by 10 to 20% in our experience - possibly not enough in late April.  Certain 2,4-D ester products are labeled for application at 1.0 lb/A when applied at least 15 days before soybean planting.

    - add metribuzin, which has burndown and residual activity on marestail.   Works especially well with Gramoxone, Liberty, or Sharpen

    - replace 2,4-D with Sharpen.  Can still be inconsistent on larger marestail.  Adding Sharpen to a glyphosate/2,4-D mixture is a more consistently effective option.

    - replace the glyphosate with Gramoxone or Liberty.  Three-way combinations of Gramoxone or Liberty plus metribuzin plus 2,4-D are strongly recommended here.  Use high rates of Liberty or Gramoxone.

    Ensuring the performance of most of the modifications listed above will require optimization of spray parameters and adjuvants.  For example, Gramoxone, Liberty, and Sharpen should be applied in a spray volume of at least 15 gpa, and MSO should be included in Sharpen-containing treatments.  Keep in mind also that use of Sharpen may necessitate a change in the residual herbicides used this spring.

    Current labeling requires mixtures of Sharpen at 1 oz/A with products containing flumioxazin, sulfentrazone, or fomesafen to be applied at least 14 days before planting on most soils.  There are no restrictions of this type for mixtures of Sharpen with any other residual herbicide, including Canopy, metribuzin, and Matador among others, which just have to be applied before soybeans emerge.  Growers who at this point know that they will be making a change in burndown programs to apply Sharpen within 14 days of planting may want to discuss residual herbicide options with their supplier before availability of certain products becomes limited.

    When we make recommendations for this situation, know that we are basing them on the average marestail population in the state.  This “average” population has a fairly high level of resistance to glyphosate and is also resistant to group 2 herbicides (ALS inhibitors – Classic, FirstRate, etc).  We know that in late spring the 2,4-D will have to carry most of the load in a mixture of glyphosate + 2,4-D, and that 2,4-D only provides about 75% control of marestail that are past the small rosette stage.  It’s possible that in some areas of the state, marestail still responds at least somewhat to glyphosate, with the result that the glyphosate/2,4-D mixture is still sufficiently active even in late spring.  Your experience can be your guide to some extent here, but know that there will be no later options to control plants that survive an ineffective burndown.

    To see an in-field Youtube video that covers this same subject, “Considerations for managing marestail in a wet spring, follow this link -  Or go to Youtube, and search for “Ohio State University Weed Science”.  Or our blog –

  5. Those Last-Minute Items on the ‘To-Do’ List Before the Planting Rush

    We all have those “I wish I had done list” – we won’t discuss how long ours are after one of these rush seasons.  Soil temperatures are:

    County Research Branch Temperature (F) on April 11
    Jackson Jackson 60.0
    Noble Eastern 58.4 
    Piketon Piketon 54.2
    Clark Western 58.1
    Huron Muck Crops 56.5
    Ashtabula Ashtabula 52.4
    Sandusky North Central 52.3
    Wood Northwest  53.8
    Wayne OARDC, Wooster 49.9

    So while you are waiting, here a few of the more common problems that end up costing yield down the road.

    1. Double check your varieties and their traits.

    a. Herbicide resistance is one of the most common, we don’t see it as often, but there is a growth in the non-glyphosate arena so to avoid a mis-application double check the bags labels.

    b. SCN resistance – for your fields with a history of SCN or those with SCN plus sudden death syndrome, make sure your varieties with the SCN resistance package gets planted there.

    c.  The same goes for Phytophthora resistance, here double check the companies fine print to determine what the partial resistance levels are (also called field resistance, tolerance etc.). Those Rps genes are good, but there is enough within field diversity in our fields in Ohio that they will not provide total protection.  Put the varieties with the “best” resistance scores on your worst fields.  Remember, especially if buying from multiple companies – every company scores a bit differently.

    d. Seed treatments – for fields with a history of replanting or poor drainage, does your seed treatment have a broad mix of fungicide active ingredients? There are not too many cases were insecticide treatment pays off in Ohio but do you have history of early-season bean leaf beetles?

    2. Field preparation—What does your field look like?

    a. Seedcorn Maggot – One of the few times an insecticide seed treatment will pay off is when you are tilling under a green cover crop and plant within 5-7 days. The decaying organic matter will attract seedcorn maggots, and which can decrease plant stand and emergence.

    b. Slugs – While there are many benefits to no-till, the residue left on the soil does promote the presence of slugs. Springs with a lot of moisture and prolonged warm temperatures (mid-60’s to 70’s) also favors higher populations of slugs. Over the next few weeks (late April/early May) is a great time to search for slugs.  Adults and perhaps even eggs can be found at this time in crop residue

  6. Pathways Project

    To help us better understand how different audiences receive and utilize manure nutrient management information, some colleagues of ours have created the Pathways Project survey. This is an important step in identifying where the gaps are in disseminating helpful information and research to users.

    With the nutrient management issues and legislation we are seeing in Ohio, it is important that everyone from producers to state agencies dealing with manure nutrient management have access to current research and information. This is a national survey but more participation from Ohio will provide us with state specific feedback.

    Please help us by taking the Pathways Project survey at: 


  7. Cover Crop Strategies Field Day


    The Cover Crop Strategies Field Day sponsored by OSU Extension of Shelby, Mercer, and Auglaize Counties and VanTilburg Farms has been rescheduled to Wednesday, April 22nd.  This follow-up to last fall’s field day will allow us to see what’s happened *below* the soil surface.

    Some of the specific points to be discussed will include managing cover crops in the spring, preparing to plant the next crop, and year-round tips for effective cover crop use.  As previously planned, the “Open House” is from 2p to 7p with informational tours scheduled at 2:30p, 4:30p, and 6p.

    Other features of the Field Day include Crop insurance implications of Cover Crops, possible EQIP Funding through NRCS.  Light refreshments will be provided.  This Field Day will be held southwest of St. Marys on SR 364, about one-half mile north of SR 219.  Look for the signs!  There is no cost to attend. 

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.


Amanda Bennett (Educator, Agriculture and Natural Resources)
Andy Michel (State Specialist, Entomology)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Mark Badertscher (Educator, Agriculture and Natural Resources)
Mike Gastier, CCA (Educator, Agriculture and Natural Resources)
Nathan Douridas, CCA (Farm Science Review Farm Manager)
Sam Custer (Educator, Agriculture and Natural Resources)
Ted Wiseman (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.

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