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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter: 2014-21

  1. Mid-Season Soybean Diseases – What can we Predict?

    Frogeye Leaf Spot: Top of leaf; classic purple border around the lesion. Below, Right: The underside of the leaf showing dusty whiskers on the bottom of lesions.
    Author(s): Anne Dorrance

    This year, there is a very high degree of variability across the state with regards to soybean height, canopy coverage, and overall crop condition.  Accordingly, the USDA planting estimates reached 85 million acres of soybean and the prices of soybean, corn, and wheat were highlighted in the Wall Street Journal last week.  What to watch for now…

    1.       Brown spot.  In all of our field plots this year, only one was no-till. This is the only one with high levels of brown spot, the unifoliates are plastered.  We have shown through 3 years of studies that brown spot typically only contributes to 3 to 4 bushels of yield loss in todays “workhorse” varieties.  If the unifoliates and lower canopy are clean as we move through flowering, then these fields do not need an application.  If you have brown spot on later planted fields, it is likely that the added costs of the application combined with the yield loss from later planting are going to hurt the overall budget for that field.  Pencil it out to be sure it is going to work for you.  Secondly – LEAVE AT LEAST 2, BETTER 3 UNTREATED strips.  At harvest, combine these 3 strips first and separately– take the average, then go through the rest of the field.  This is the best information of any if these mid-season applications are bringing a return to your farm.

    2.       Frogeye leaf spot.  We have a couple of locations that we have been monitoring in the state where we know frogeye has overwintered in the past.  I was almost fooled last week as when we got to the site, lots of necrotic spots with purple borders were everywhere – note I said everywhere.  Many of the herbicides that the weed group is recommending to combat weed resistance will also cause the characteristic purple border.  The difference – if it is frogeye leafspot, caused by the fungusCercospora sojina, the spots will have “whiskers” on the underside of the leaf in the spot (technically called conidia).  In Kentucky and in Indiana there are populations of this fungus that are resistant to the strobilurins (Headline, Quadris etc); we are participating in a regional study to monitor for the presence of these insensitive strains, so again, please send me leaves.  Place them in a plastic bag without any extra paper.  Put them in a padded mailer and they should arrive just fine.

    3.       White mold.  This is targeted to those producers who have been dealing with white mold for a long time.  This cool wet weather we are having definitely fits the conditions necessary for white mold development.  So for highly susceptible varieties it is time to put the first spray on which should occur at the first flower.  Remember, white mold does not suddenly appear, a field is infested with the sclerotia, hard black fruiting bodies which serve as the survival structure.  Under the types of conditions we are having and with canopy closure they are perfectly timed to produce a very small mushroom which can produce hundreds of spores.  These land on the flowers, they need the sugar to begin to germinate and infect the plant at the node.  Last year in the northeastern part of the state, we had our fungicide trial using a moderately resistant cultivar.  Even though conditions were perfect for disease, we only had approximately 20% disease severity in our non-treated plots and over 65 bu yields.  The fungicide applications did not help.  Admittedly, I think we were 3 days late in our applications, but I was also pleasantly surprised at how little disease actually developed.  We have 2 studies out this year to examine a variety x fungicide effect, but  I do think the seed companies have done a very good job in incorporating resistance into the current cultivars.  Again, if you have some questions, leave 2 to 3 strips to see for yourself what the variety resistance is going to do for your overall management.  Fungicides, we have had success in some trials with the fungicides Aproach and Topsin M.  Headline is not recommended for management of white mold as several University trials, including at least one of mine we have doubled the disease severity with applications of pyraclostrobin.  Herbicides are even more challenging this year since the soybeans are so delayed, again, leave the strips.

    4.       Soybean Rust.  The impact of the last winter can readily be seen with how little soybean rust survived in the south.  Last week was the first report from Alabama in 2014 (  Remember this is the first pustule identified in county turns a county red on the USDA IPM Pipe map.  We are a long way from build-up at this time.  Again, many thanks and gratitude to my colleagues in the southern states for their efforts to keep monitoring for this pathogen. 

  2. Corn Silking in Some Fields

    Author(s): Peter Thomison

    According to the National Agricultural Statistics Service ( for the week ending 7-6-14, 4% of the state’s corn was silking which is in line with the 5-year average. Given the wide range in corn planting dates this year, some late planted (corn planted in early-mid June) will not achieve tasseling and silking until August. The pollination period, the flowering stage in corn, is the most critical period in the development of a corn plant from the standpoint of grain yield determination. Stress conditions (such as hail damage and drought) have the greatest impact on yield potential during the reproductive stage. The following are some key steps in the corn pollination process.

     Most corn hybrids tassel and silk about the same time although some variability exists among hybrids and environments. On a typical midsummer day, peak pollen shed occurs in the morning between 9:00 and 11:00 a.m. followed by a second round of pollen shed late in the afternoon. Pollen may be shed before the tassel fully emerges. Pollen shed begins in the middle of the central spike of the tassel and spreads out later over the whole tassel with the lower branches last to shed pollen. Pollen grains are borne in anthers, each of which contains a large number of pollen grains. The anthers open and the pollen grains pour out in early to mid morning after dew has dried off the tassels. Pollen is light and is often carried considerable distances by the wind. However, most of it settles within 20 to 50 feet.  

     Pollen shed is not a continuous process. It stops when the tassel is too wet or too dry and begins again when temperature conditions are favorable. Pollen stands little chance of being washed off the silks during a rainstorm as little to none is shed when the tassel is wet. Also, silks are covered with fine, sticky hairs, which serve to catch and anchor pollen grains.

     Under favorable conditions, pollen grain remains viable for only 18 to 24 hours. However, the pollen grain starts growth of the pollen tube down the silk channel within minutes of coming in contact with a silk.  The pollen tube grows the length of the silk and enters the female flower (ovule) in 12 to 28 hours. A well-developed ear shoot should have 750 to 1,000 ovules (potential kernels), each producing a silk. The silks from near the base of the ear emerge first and those from the tip appear last. Under good conditions, all silks will emerge and be ready for pollination within 3 to 5 days and this usually provides adequate time for all silks to be pollinated before pollen shed ceases.

     Pollen of a given plant rarely fertilizes all the silks of the same plant. Under field conditions 97% or more of the kernels produced by each plant may be pollinated by other plants in the field. The amount of pollen is rarely a cause of poor kernel set. Each tassel contains from 2 to 5 million pollen grains, which translates to 2,000 to 5,000 pollen grains produced for each silk of the ear shoot. Shortages of pollen are usually only a problem under conditions of extreme heat and drought. As noted above, poor kernel set is more often associated with poor timing of pollen shed with silk emergence – with silks emerging after pollen shed (poor “nick”). However, hybrids rarely exhibit this problem unless they experience extreme drought stress. Some of the new drought tolerant hybrids have shorter “anthesis silking intervals”, i.e. pollen shedding and silk emergence are more closely synchronized, than hybrids more susceptible to drought. This shorter anthesis silking interval may mitigate the impact of drought stress during pollination.

     For more on the pollination process in corn check out the following.

     Abendroth, L.J., R.W. Elmore, M.J. Boyer, and S.K. Marlay. 2011. Corn growth and development. Iowa State Univ. Ext. PMR 1009.

     Nielsen, R.L. 2010. Tassel Emergence and Pollen Shed. Corny News Network, Purdue Univ. [On-Line]. Available at (URL verified 7/7/14).


    Nielsen, R.L. 2010. Silk Development and Emergence in Corn. Corny News Network, Purdue Univ. [On-Line]. Available at (URL verified 7/7/14).

  3. Nutrient Value of Wheat Straw

    With wheat harvest underway, we often get questions about the nutrient value of straw.  The nutrient value of wheat straw is influenced by several factors including weather, variety, and cultural practices.  Thus, the most accurate values require sending a sample of the straw to an analytical laboratory.  However, “book values” can be used to estimate the nutrient values of wheat straw. 

     In previous newsletters, we reported that typically a ton of wheat straw would provide approximately 11 pounds of N, 3 pounds of P2O5, and 20 pounds of K2O.  A 2013 analysis of wheat straw collected at the OARDC farm in Wooster contained 14-18 pounds of N, 3-4 pounds of P2O5, and 20-23 pounds of K2O.  These values were across four wheat varieties and three spring nitrogen application rates (60, 90, and 120 lb N/acre).  The 2013 values corresponded fairly well with the previously reported “book values.”  Nitrogen values in 2013 were slightly greater than “book values” which may have been a result of wheat height/size.  If plants are shorter/smaller, percentage nitrogen tends to be greater than taller/larger plants due to a dilution factor as the plant grows. Regardless, the 2013 analysis provides validity to the nutrient value of straw given in previous newsletters.

     The nitrogen in wheat straw will not immediately be available for plant uptake.  The nitrogen will need to be converted by microorganisms to ammonium and nitrate (a process called “mineralization”).  Once the nitrogen is in the ammonium and/or nitrate form, it is available for plant uptake.  The rate of which mineralization occurs depends on the amount of carbon and nitrogen in the straw (C:N ratio).  The USDA reports a C:N ratio of 80:1 for wheat straw which means there are 80 units of carbon for every unit of nitrogen.  Mineralization rapidly occurs when the C:N ratio is ≤ 20:1.  At a C:N ratio of 80:1, mineralization will be much slower.  (For comparison, corn stover is reported to have a C:N ratio of 57:1.)  Rate of mineralization is also influenced by soil moisture and temperature.  Since mineralization is a microbial-driven process, mineralization will be slowed (halted) in the winter when temperatures are cold. Thus, no N credit is given for wheat straw since it is not known when the N will mineralize and become available to the following crop.

    Besides providing nutrients, straw has value as organic matter, but it is difficult to determine the dollar value for it.  Removal of straw does lower soil potash levels.  If straw was removed after heavy rainfall, some of the potash may have leached out of the straw, lowering the nutrient value of the straw.  However, a soil test should be done to accurately estimate nutrient availability for future crops.

  4. "Late" Applications of Nitrogen to Corn

    Author(s): Peter Thomison,

    Persistent rains this year may force many growers to sidedress their nitrogen (N) in corn this year much later than what is considered normal. Other growers may be supplementing their earlier N applications to replace N lost from denitrification and leaching. The following are some suggestions from extension soil fertility specialists at Ohio State and Purdue University from past years that address various questions concerning N applications to corn after planting.

    HOW LATE CAN N BE APPLIED? Corn utilizes large quantities of N during the grand growth stage. From the 8 leaf stage through tasseling N uptake is 4 to 8 pounds per day. For most corn hybrids N uptake is complete shortly after pollination. So, most of the N should be applied prior to the 10 leaf stage, with any supplemental applications complete by or shortly after tasseling.  Under conditions of severe N deficiency, some response would be expected to low rates of N (30 to 60 pounds) as late as three weeks after pollination.

    WHAT IS THE BEST N SOURCE TO USE? Ammonia or N solutions knifed in are preferred in most situations, especially high residue fields. Granular urea can also be applied over the top in clean tilled situations, but those applications can be risky if rainfall does not come shortly after application.  Urea stabilizers (Agrotain) should be considered in high residue situations.  Granular urea broadcast in standing corn will cause some foliar burn when granules fall into the whorl. While it may appear unsightly, little yield decrease normally occurs if the fertilizer is applied prior to the 10-leaf stage.

    HOW MUCH N SHOULD BE APPLIED? If the corn has gotten too tall to sidedress by this point (mid to late June), it has probably not been severely stressed and yield potential is still good. An example would be rotation corn after beans which had some starter or 28% applied with herbicides with good green color. Nitrogen rates should approach what was initially planned at the beginning of the season.  Research at Ohio State shows that decreased rates can do well, but do not decrease rates by more than 10-15%.  

    CAN I BROADCAST 28-0-0 SOLUTIONS "OVER THE TOP"? Using broadcast applications of 28% N solution to sidedress N will cause some burn to foliar tissue of corn plants. 
    The severity of injury is determined by the plant's stage of growth, the amount of N used and form of N. If the plant growing point is at or below the soil surface (or when plant has six collared leaves or less), the extent of foliar injury caused by burn will usually be negligible if the N rate is kept below 50 lb/acre. Even with higher N rates at later vegetative growth stages the injury from leaf burn is normally not so severe that it outweighs the potential benefits received from the N addition. The degree of plant burning is less with urea granules than with other N products.

    Dribbling 28% solution with drop nozzles as a narrow band on the soil surface is an alternative approach that can help reduce foliar burning. Dribbling 28% is also a more efficient use of N than broadcast surface application because it helps reduce N volatilization.  Urea stabilizers may be considered for this application, but tillage is a major deciding factor on whether or not they are necessary.  High residue corn fields may benefit from urea stabilizers, but low residue fields are less likely to benefit.  At this point of the growing season, and the need for plenty of nitrogen by the crop, we do not recommend nitrification inhibitors.  We also rarely see positive responses to nitrification inhibitors when N is sidedressed.

    CAN I APPLY N TO EVERY OTHER ROW? Research in Indiana, Illinois and Iowa has all shown that farmers can knife ammonia or N solutions in every other row middle (60 vs. 30 inch spacing) with no reduction in yield. The only caution is that extra attention must be paid, especially in wet conditions, that no knives plug with soil. A plugged knife in 60 inch spacing gives 4 rows with no N and will seriously reduce yields.

    Another article on this topic published by Purdue University in 2011 can be found here:

  5. First Generation of Roundup Ready Soybean Trait Patent Set to Expire in 2015

    Author(s): Laura Lindsey

    The first generation of the RoundUp Ready® (RR1) soybean trait patent is set to expire in 2015.  This means that farmers can save seed with the RR1 trait for replant in spring 2015 if there are no other patents on the seed.  Farmers will need to check with their seed supplier before replanting saved seed.  Soybean seed can have both trait (i.e., RR1) and variety patents.  Although, the RR1 trait patent is set to expire, there may be other trait patents and/or variety patents that prohibit replanting saved seed.  If a farmer is legally able to save and replant soybean seed, the seed cannot be transferred or sold to another farmer.  Genuity® Roundup Ready 2 Yield® (RR2Y) soybeans are protected under a different patent than RR1 soybeans.  Therefore, it is illegal to save and replant RR2Y soybean seed.   

    Patents help fuel research and development by granting companies exclusive rights to make, use and sell the patented technology for a limited amount of time (usually 20 years).  Without patents, there would be little incentive for companies to invest in research and development of new technologies.

    For detailed information regarding the RR1 trait expiration please see:

  6. Register Now for Western ARS Agronomy Field Day

    Please register and plan to attend the OSU Extension and OARDC Western ARS Agronomy Field Day on July 16. Preregistration required for meal count by July 11, payable at the door $20. Register by email or phone to: Harold Watters (, 937 599-4227 or Joe Davlin (, 937 462-8016.

    Check-in is from 8:30 AM to 9

    ·         Wagon tour running from 9 to noon.

    ·         Lunch will include a meal and brief updates.

    ·         Choose one afternoon program from 1PM to 3PM with about an hour each with state Extension specialists.

    CCA CEUs will be available. The Ohio Soybean Council provides support for our program. The new Field Guide for Corn, Soybean, Wheat and Alfalfa will be available for sale.

    The location is the Western Agricultural Research Station, 7721 South Charleston Pike, South Charleston, Ohio 45368

  7. New Corn, Soybean, Wheat, and Alfalfa Field Guide Available

    With late crop development this year, we still have a lot of crops to walk. One excellent tool is the Corn, Soybean, Wheat and Alfalfa Field Guide – newly updated and in a new format this year will help with this chore. The Field Guide is available on OSU Extension’s eStore for sale, and may be ordered from county Extension offices as well.

     This link is to the store for the hard copy version:; the price is $12.50.

     Many use their droid or iPad in the field and there is a digital version available now too:, for $10.

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 Douridas, CCA (Educator, Agriculture and Natural Resources)
Andy Michel (State Specialist, Entomology)
Bruce Clevenger, CCA (Field Specialist, Farm Management)
Eric Richer, CCA (Field Specialist, Farm Management)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Les Ober, CCA (Educator, Agriculture and Natural Resources)
Mark Badertscher (Educator, Agriculture and Natural Resources)
Mike Gastier, CCA (Educator, Agriculture and Natural Resources)
Nathan Douridas, CCA (Farm Science Review Farm Manager)
Pierce Paul (State Specialist, Corn and Wheat Diseases)
Sam Custer (Educator, Agriculture and Natural Resources)
Sarah Noggle (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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