Corn Newsletter : 2016-18

  1. Have and have nots across state when it comes to rain over the last week

    Author(s): Jim Noel

    Ohio is the state of have and have nots when it comes to rain. Scattered areas of very heavy rain next to limited rain occurred over the last week. Rainfall over Ohio the last week ranged from less than 0.10 inches to over 5 inches. Most places experienced 0.50 to 2 inches.

    Attached is the region's rainfall for the last 7 days.

    The outlook for the next 7-10 days calls for below normal rainfall. Rainfall through July 6 across Ohio will generally be under 0.25 inches so things will be drying out in a hurry into the 4th of July holiday.

    The last week of June will see near normal temperatures and rainfall generally under 0.25 inches except isolated high totals.

    The first week of July will see above normal temperatures return with a heat dome building to the west again. Around this heat dome will be disturbances which brings the risk of storms and localized heavy rain back to the state of Ohio between July 7-13.

    Overall, July is forecast to be warmer and drier than normal. However, extreme maximum temperatures above 95 will also be limited which is good news. Pockets of heavy rain will occur into July but the overall patterns favors slightly drier than normal conditions.

    You can see all the latest NOAA information for the region at:

  2. Mid-season diseases – what are we watching out for?

    Author(s): Anne Dorrance

    I’ve scouted a number of fields and driven by many acres in the past two weeks and the crop looks great.  A bit behind in some areas, but soybeans can compensate fairly well.  With that comes the question what do we need to watch out for next.

    1. Frogeye leaf spot– particularly in those fields where it was present at high levels last year and the field is in soybean this year.  I will assume that this practice was done due to the late planting date and not a continuous soybean practice.  In these fields there is a higher probability that frogeye leaf spot will start early.  If you do find spots, gray lesions with purple borders, look on the underside to see if there are whiskers (spores) on the bottom of the lesion.
    2. Lots of noise about soybean rust this year.  This is the first year that levels are high in the very deep south:  Florida, Alabama, Mississippi, and Louisiana.  The good news is that the hot, dry weather forecast for most of this summer should keep it in check.  In the past, from the sentinel plot surveys we have noted that once a pustule is found (1/100 leaves) – that this gives a 3 week notice.  Unlike our southern producers who have spore deposits every day – Ohio and northern states have to wait for a large wet weather event to bring the inoculum in.  It must then multiply in the field (9 to 10 days from inoculation to sporulation) and build-up with the field.  To date no weather event has occurred and we will continue to monitor the situation especially for those late planted soybeans.
    3. Brown spot – where did it go?  I have been very surprised at how clean the lower leaves and unifoliates are this year, even in no-till fields.  This is really an indication of how dry it was for the time period following planting in many areas of the state.  We will see how it looks next week after several rain events.
  3. Low Head Scab and Vomiitoxin and Very Good Grain Yield and Quality

    A June 27 Update: Wheat is now drying-down and is even being harvested in some parts of the state. Thanks in part to cool spring conditions followed by relatively dry weather during early grain-fill, head scab and other disease levels were generally low in most areas; and low disease severity often means very good grain yield and quality. Stripe rust was our biggest disease problem this year, but outbreaks only occurred in pockets within and across fields. Moreover, several of the affected fields were treated with a fungicide which helped to keep this and other later-season diseases in check.

    The first set of harvest numbers are showing yields above 80 bushels per acre and test weight in the upper 50s. While we expect these numbers to vary from field to field, once the rain stays away as harvest continues, we expect to continue seeing very good grain yield and quality. Lodging is being reported I some fields, but unless it becomes very windy and rainy over the next few weeks, this will likely not be a major problem. However, getting the wheat off as soon as possible will minimize the chance of lodging and other late season problems. If you opt to harvest early (moisture in the upper teens or lower 20s), make sure you dry the grain down to minimize post-harvest problems.

  4. Spray Diagnostics Field Day

    Author(s): Jeff Stachler

    Enlist corn and soybean and Xtend soybean are getting closer to reaching the market place.  With these new technologies spray drift, herbicide volatility, and tank contamination will need to be addressed.  On July 14, 2016, OSU Extension of Auglaize and Mercer Counties will host a Spray Diagnostics Field Day from 10 AM to Noon at 14739 Kruse Road (Bob Engle farm), Wapakoneta, Ohio.  Spray nozzle selection, herbicide mode of action symptoms, spray drift, and tank contamination will be discussed.  Drs. Erdal Ozkan and Jeff Stachler will be presenting.  The cost of the program is $10.00.  Preregistration is requested by July 7, 2016.  Contact the Auglaize (419-739-6580) or Mercer (419-586-2179) County Extension offices to register.  Commercial PAT and CCA credits will be available.  Come and see the herbicide symptoms on tomatoes, green beans, pumpkins, corn, and soybean.

  5. North American Manure Expo

    Author(s): Amanda Douridas

    The North American Manure Expo is returning to Ohio August 3-4, 2016 for the first time in eight years. This top notch event provides ample opportunity to learn more about manure nutrient management and see the latest industry technology and equipment. The theme for the 2016 expo is Manure: Returning Nutrients to Their Roots. The Expo will be held at the site of the Farm Science Review north of London.

    August 3rd begins with tours of farms and agribusinesses focusing on nutrient management practices. There are three morning tours to choose from including dairy, beef, and composting and nutrient management which run from 9-noon. All tours will end at the agitation demonstrations at Newport Dairy. Participants can also take a bus straight to the agitation demos from the expo site if they are unable to participate in the morning tours. The morning tours have a registration fee of $20 which includes transportation and lunch. Space is limited so register today at:

    The Expo grounds will open on August 3 from 3pm-8:30pm and August 4 from 7:30am-6:00pm. Over 90 companies are participating in the trade show and there will be a number of education sessions throughout the evening of August 3 and all day August 4. Manure application demonstrations will take place on August 4th and will include liquid and solid manure applicators, drag hose sidedressing corn, and compost turning. For a full schedule of the expo and to registration for the Manure Expo, please visit:

    Check out the Manure Expo Clip here: 


  6. Flooding and ponding injury to corn -- "Muddied Corn"

    Author(s): Peter Thomison

    Heavy rains during the past week have resulted in flooding and ponding in Ohio corn fields. In some localized areas, this may have resulted in partial and complete immersion of corn plants, especially in low spots and in river bottoms and along streams. When water drains off these fields, plants may be covered to varying degrees with a layer of mud. Will corn plants covered by a layer of mud survive and can it perform normally? The layers of silty mud covering plants will limit or prevent leaf photosynthesis. Bacteria deposited in leaf whorls by flooding can result in disease and kill plants. On the positive side, most corn in Ohio was at a stage of growth less vulnerable to flood damage when it occurred. Corn planted through late May should be well beyond V6 (the six leaf collar stage) when the growing point is at or above the soil surface and less sensitive to flooding and associated anaerobic soil conditions. If the duration of flooding was brief, limited to several hours, and temperatures were moderate, damage should be minimal. Moreover, if corn was subjected to flooding at mid-vegetative stages of development, most leaves on affected plants should not be severely impacted by the mud coatings (assuming that mud in the whorl does not inhibit normal emergence of subsequent leaves). Corn plants produce up to 21 leaves, so at V10, about half the corn leaves have yet to emerge from the whorl. The leaves that have yet to emerge are the most important for the corn plant because the upper canopy produces most of the corn plant’s yield potential. According to the National Crop Insurance Service’s defoliation charts, complete leaf loss at about V10 results in 28% yield loss. However, it’s unlikely that the photosynthetic capacity of leaves has been completely destroyed in plants covered with mud. Rain this week will wash silt off leaves allowing for resumption of photosynthesis. It will also help wash mud out of leaf whorls allowing new leaves to emerge. 

  7. How Can the Timing of Stress Affect Yield in Corn?

    Extreme weather events have begun again in 2016 with renewed force. Frost damage in May impacted early planted corn in parts of the state, with exposed leaf tissue showing extreme necrosis. Alternating periods of wet and dry conditions has also led to some variability in crop stage in some fields. Corn ear development occurs throughout the growing season, and extreme temperature or moisture stress at different growth stages will decrease different aspects of grain yield. Below is a quick summary of the yield component most affected by environmental stress at different growth stages:

    • Before V5: The growing point is typically protected from extreme temperature fluctuations below the soil surface, and should be able to overcome early-season leaf damage. Soil crusting may impact ease of emergence, which could result in some stand variability. Uneven or late emergence can impact the yield potential by limiting the light quality received and causing competition with plants that emerged earlier.
    • V5-7: Number of kernel rows. Corn plants are determining the number of kernel rows as early as V5 in some corn hybrids. By V7, the number of kernel rows in the primary ear has been determined for most hybrids.
    • V9-VT: Number of potential kernels per row (row length). Each potential kernel comes from one floret on the ear (female flower), and as conditions are more favorable for development the plant will initiate more florets. The number of potential kernels on the ear can be set through late vegetative stages (through V16). Stress during this phase can reduce the yield potential of each plant, and can limit overall yield potential of a field. Flex-ear hybrids may initiate more kernels as compared to a fixed-ear hybrid during this stage.
    • VT/R1: Number of potential kernels that are fertilized. Pollination is a critical stage in producing yield. If the florets are not pollinated, a harvestable kernel will not develop. High temperatures and moisture stress can cause pollen release to occur before silk emergence resulting in poor pollination, and can decrease pollen grain viability. Ear elongation is occurring during R1, and if stress occurs total ear length could be decreased. Yield losses have been estimated up to 13% per day of stress.
    • R2-R3: Kernel number to be filled. Stress at the blister (R2) and milk (R3) stage can cause fertilized kernels to be aborted due to poor carbohydrate availability. Carbohydrate production will decrease as temperature and moisture stress increase because photosynthesis is reduced. The limited production of sugars will cause the plant to abort kernels, typically those that were the last to be pollinated (at the tip).
    • R4-R5: Kernel size. At the dough (R4) and dent (R5) stages, carbohydrate accumulation within the kernels will be reduced due to environmental stress. At the start of R5, only 45% of the dry matter in each kernel has been accumulated, leaving half of the starch to be added during R5. However, the kernel contains 90% of its dry matter halfway through the R5 growth stage (milkline halfway down the kernel). Early season frosts during this stage can reduce final grain yields by preventing starch accumulation before maturity (R6).


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

    Shaw, R.H. and J.E. Newman. 1991. Weather stress in the corn crop. Purdue Univ. Coop. Ext. Serv. NCH-18.

  8. Flooded Soybeans in Some Areas of the State

    Author(s): Laura Lindsey

    June 22-23, some areas of Ohio received a significant amount of rain with some areas receiving as much as 4 to 5 inches.

    When plants are completely underwater for approximately 24-48 hours under high temperatures (>80°F), they will likely die.  Plants respire more under high temperatures, oxygen is depleted, and carbon dioxide builds up suffocating the plant.  Cool, cloudy days and cool, clear nights increase the survival of a flooded soybean crop.  If the waters recede quickly and the plants receive some light rain, they can recover.

    Under wet conditions, soybeans may turn yellow and also be somewhat stunted. This is often indicative of poor nodulation.  Nodules are the small knots found on roots, often near the top of the root system.  Nodules are the result of a symbiotic relationship between soybean and bacteria (Bradyrhizobium japonicum).  These bacteria convert nitrogen into a form that is usable by the soybean plant. Nodulation is reduced in wet soils.  Soybeans at the V2 growth stage when grown in saturated soil for two weeks retain the ability to recuperate nodule function when normal (aerobic) conditions are restored.  To determine if a nodule is actively fixing nitrogen (i.e., converting nitrogen to a usable form), split the nodule with your fingernail and examine the inside.  If the inside of the nodule is pink or red, nitrogen is being fixed.


    Henshaw, T.L., R.A. Gilbert, J.M.S. Scholberg, and T.R. Sinclair. 2007. Soya bean (Glycine max L. Merr.) Genotype response to early-season flooding: I. root and nodule development. J. Agronomy & Crop Science 193:177-188.  

  9. Potato Leafhopper in Alfalfa

    Although populations of potato leafhopper on alfalfa have been somewhat low in June, a few locations are reporting growing numbers.  Second cut has happened or is happening in many locations.  But if alfalfa is more than 7 days from a cut, a rule of thumb threshold for plants under normal stress is:  when the average number of leafhoppers in a single sample (10 sweeps) equals or is greater than the height of the alfalfa, treatment should be considered if harvest is more than 7 days away. For example, if the alfalfa is 8 inches tall and the average number of leafhoppers per sample is 8 or higher, treatment is warranted. If the average is 7 or lower, the grower should come back within a few days to see if the population is higher or lower.   

    Vigorous alfalfa can tolerate higher numbers, and stressed alfalfa can tolerate fewer.  The threshold should be lowered when the alfalfa is under stress, especially for new seedings made this year. Consider lowering the threshold to half the normal level for new seedlings that are growing slowly because of drought stress. In those situations, there may NOT be a yield response from insecticide treatment in the current growth cycle, especially if drought conditions persist.  However, protecting the plants from leafhopper damage now will protect the stand, development of the taproot,  and its future yield potential. Potato leafhopper resistant varieties can also tolerate higher numbers. Our data to date indicate the threshold for PLH resistant varieties in established stands is 4 times the normal threshold. More information about potato leafhopper scouting and thresholds in alfalfa can be found at

  10. Two-spotted Spider Mite Awareness

    Though we have not received many reports of spider mites in field crops, continued hot dry weather will favor this pest, and scouts should keep their eyes open for mites and their stippling damage.  We will provide a more comprehensive article later in the season if reports indicate that spider mites are on the rise.  For more information, see  

  11. Nutrient Management Field Days Announced

    Registration and program agendas are available for two upcoming Nutrient Management Field Day events being hosted at OARDC Branch Stations. These programs provide the opportunity for a demonstration approach to Fertilizer Applicator Certification Training (FACT) while highlighting nutrient/water quality research being conducted at these locations. Information on nutrient sources of commercial fertilizer and manure are included.

    Details on the individual programs can be found at the links below:

    Both programs begin at 9 am and finish by 2:30 pm. Pre-registration is required, with a $15 registration fee that covers lunch. Payment can be made with credit card.

    The agenda will feature nitrogen management, phosphorus management, water quality and equipment for fertilizer placement. Each program varies slightly to utilize on-site resources. Refer to the site agenda for complete details.

    General topics covered:

    • Nitrogen management will cover pre-sidedress Nitrogen soil test for N, use of NDVI meters in N rate determinations, using maximum return to nitrogen models and late season N applications.
    • Phosphorus management will include results of long term P and K studies, reading a soil test report and determining P fertilizer rates.
    • Water quality will include nutrient movement from edge of field results and drainage water management recommendations
    • Field demonstration will include:
    • Equipment for granular fertilizer placement and late season N application to corn.
    • Using manure as a nutrient source to replace commercial fertilizer purchases and fully utilize N.

    Please note a similarly formatted field day is planned for September 14th at the FSR site London, OH. Announcement and registration for this event will occur in early August.

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.


Amanda Bennett (Miami County)
Amanda Douridas (Champaign County)
Andy Michel (State Specialist, Entomology)
Anne Dorrance (State Specialist, Soybean Diseases)
Clifton Martin (Muskingum County)
David Dugan (Adams County)
Debbie Brown, CCA (Shelby County)
Dennis Riethman (Mercer County)
Greg LaBarge, CPAg/CCA (Field Specialist, Agronomic Systems)
Jeff Stachler (Auglaize County)
John Barker (Knox County)
Kelley Tilmon (State Specialist, Field Crop Entomology)
Lee Beers, CCA (Trumbull County )
Les Ober, CCA (Geauga County)
Mark Badertscher (Hardin County)
Mary Griffith (Madison County)
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)
Steve Culman (State Specialist, Soil Fertility)
Ted Wiseman (Perry County)
Tony Nye (Clinton 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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