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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter: 2016-30

  1. Diplodia Ear Rot

    Over the last two weeks, we have received several samples of corn ears with symptoms typical of Diplodia ear rot. This is one of the most common ear diseases of corn in Ohio. It is caused by two species of fungi, Stenocarpella maydis and Stenocarpella macropora. The most characteristic symptom and the easiest way to tell Diplodia ear rot apart from other ear diseases such as Gibberella and Fusarium ear rots is the presence of white mycelium of the fungus growing over and between kernels, usually starting from the base of the ear. Under highly favorable weather conditions, entire ears may become colonized, turn grayish-brown in color and lightweight (mummified), with kernels, cobs, and ear leaves that are rotted and soft. Rotted kernels may germinate prematurely, particularly if the ears remain upright after physiological maturity. Corn is most susceptible to infection at and up to three weeks after silk emergence (R1). Wet conditions and moderate temperatures during this period favor infection and disease development, and the disease tends to be most severe in no-till or reduce-till fields of corn planted after corn. The greatest impact of this disease is grain yield and quality reduction. Mycotoxins have not been associated with this disease in US, although animals often refuse to consume contaminated grain.


    1. Can disease severity increase on the field? When should we harvest? What moisture should we start?

    The disease will continue to develop in the field as long as conditions remain favorable. Fields with high incidence of Diplodia ear rot should be harvested as soon as possible and quickly dried to 14% moisture and cooled to 50oF before storage. Ideally, fields should be scouted to identify areas with Diplodia ear rot hot spots and these areas should be harvested and stored separately from grain harvested from healthier sections of the field. Higher moisture, warm conditions, and pockets of moldy grain in storage will lead to further spread of the disease and even colonization of the grain with other pathogens.

    1. How should the combine be set? Cobs are very soft.

    Rotted kernels and cobs are broken into small pieces during harvest, increasing the amount of fine particles in the grain. These particles affect airflow through the grain, delay drying, and lead to further mold development in storage. Increasing the combine fan speed will help remove fine materials as well as severely infected kernels that are usually lighter than healthy kernels. The specific adjustments needed to remove moldy materials during harvest will vary from one combine to another; see manufacture’s guidelines for details on how to increase your combine fan speed.

    1. Will it get worse in the bin? How dry should it be dried? How long can we store it?

    Clearing the grain to remove fine particles and storing it under cool, dry conditions (50F and 14% moisture) will slow-down fungal growth and mold development and extend the storage life of the grain at least through the winter. However, you should avoid storing severely affected grain for too long especially since it becomes much more difficult to keep grain cool and dry as outside temperatures increase in the spring and summer. 

    1. Do we need to worry about vomitoxin and feeding?

    No, vomitoxin is a mycotoxin produced by Fusarium graminearum, the fungus that causes Gibberella ear rot of corn and head scab of wheat. However, some populations of S. maydis, the fungus that caused Diplodia ear rot, do produce a different mycotoxin calling diplodiatoxin, but there have been no reports of animal-health problems associated with this toxin in the US. Nevertheless, since animals often refuse to consume moldy grain, you should avoid feeding grain affected by Diplodia ear rot to animals. In addition, moldy grain may be contaminated with other fungi, some of which do produce mycotoxins that are harmful to livestock.

    1. What does next year bring? We know hybrid selection is important. Does the residue need to be buried?

    Yes, since the fungus survives in crop residue on the soil surface, any strategy to remove or bury the residue will reduce the risk of Diplodia ear rot (and other residue-borne diseases) next year. In addition, fields and hybrids with high incidence of Diplodia ear rot this year should be avoided next season. However, whether or not we have a similar problem with this disease next year will depend on the weather.

    1. Would a fungicide have made a difference?

    Very little research has been done to evaluate the efficacy of fungicides against Diplodia ear rot. Although most of the common fungicides kill the fungus in the lab, results in the field have been highly inconsistent. More research is needed to improve application technology and to decide when the fungicide should be applied to effectively control Diplodia ear rot.

  2. Moldy Corn, Kernel Sprouting and Upright Ears

    Moldy ear and kernel sprouting problems have been reported in parts of Ohio especially west central and NW Ohio. The title photo by Sam Custer, Extension Educator in Darke County and the photo below by Dr. Pierce Paul is a good illustration of what is being found in some fields:

    The moldy ears have been attributed primarily to Diplodia ear rot (see article in this issue of the C.O.R.N. newsletter by Dr. Pierce Paul). As has been the case in past years, the moldy ears and kernel sprouting are often associated with upright ears. Ears that remain erect after physiological maturity (black layer development) are more likely to promote molds and kernel sprouting because they trap water (especially at the base of the ear and slow kernel drying. These ears may also be affected by opportunistic organisms taking advantage of the moist, nutritious environment at the base of the ear.

    There are several factors that determine whether a corn ear remains erect or “droops” (points downward) following physiological maturity. Ears of corn normally remain erect until sometime after physiological maturity has occurred (black layer development), after which the ear shanks eventually collapse and the ears droop (Nielsen, 2011). However, ears may droop in drought-stressed fields that have not yet reached physiological maturity.  A loss of turgidity in the ear shank due to water stress, possibly combined with some cannibalization of carbohydrates in the ear shank may eventually cause the ear shank to collapse, resulting in ear drooping. In certain hybrids, ears remain upright following physiological maturity (or remain erect for a longer duration) which can be related to a shorter ear shank.  According to some seed company agronomists, prior to the development of Bt hybrids, corn breeders tried to reduce ear drop due to European corn borer damage by shortening ear shanks. Some of that germplasm has continued to be used in more recent hybrids. These agronomists acknowledge the concerns that upright ears are slower to dry or more prone to ear molds and indicate that companies are looking for more droopy shanks to help protect ears from water damage. However, they contend that there are other genetic components to these traits and that the effects of upright ears on fungal infections may not be as pronounced as is widely thought.

    In addition to genetic differences among hybrids, environmental conditions and cultural practices may affect ear orientation during the drydown period prior to harvest. In ongoing OSU field research that compares multiple hybrids varying in maturity at two SC and NW Ohio locations, differential responses to plant population for % ear erectness (at maturity) were observed. At these test sites, % erect ears usually decreases significantly as plant population increases. These results suggest that factors other than hybrid genetics can determine if an ear is in an erect or droopy position at harvest. For more on ear rots and kernel sprouting, check out the following -  “Troubleshooting Abnormal Corn Ears” online at


    Nielsen, R.L. 2011. Are Your Ears (of corn) Sagging? Corny News Network, Purdue Univ. [On-Line]. Available at (verified 9-19-16)

  3. Farm Science Review 2016: Last Minute Reminders

    Harvest has started in some areas of Ohio. At the Farm Science Review we have some of the crop off to allow demonstrations to begin. Field demonstrations will include soybean and corn harvest, of course; plus drones/UAVs, soil sampling, planters, precision nutrient placement and drainage installation.

    Visit the Agronomic Crops Team. We will again be the welcoming crew as you enter the grounds from the public parking lot on the east side of the exhibit area. We can talk about weeds, insects or disease; continue on with a discussion about corn and soybean production practices and more. We also have in place long-term demonstrations on soil quality along with several cover crops. New this year are presentations at 10:00 am and 2:00 pm every day on nitrogen management, choosing sprayer tips for herbicide tolerant crops, soil quality, and weed identification. Stop off in the Agronomy Plots as you arrive or on the way out. 

    CCAs can get continuing education credits at the Gwynne Conservation area, the Small Farm Center and with us in the Agronomy Crops Team Plots, watch for the FSR CCA College signs.  Presentations that offer CCA credits are noted on the Farm Science Review Demonstration and Event Schedule that is available on line at, then click on the visitors tab to find the schedule.

    The Farm Science Review app, which can be used on both Apple and Android smartphones and tablets, can be downloaded in the Apple App Store or the Google Play Store by searching for “FSR 2016,”With the app, users can:

    * View the complete show schedule and create a personal schedule.

    * View detailed session information, including speaker bios.

    * Provide feedback on sessions.

    * View a show map.

    * Locate food vendors.

    * View exhibitor information.

    * Connect with Farm Science Review on Facebook and Twitter.

  4. Considering Growing Wheat in Wide Rows?

    Growers may be interested in wide-row wheat production due to reductions in equipment inventory (lack of grain drill) and to allow intercropping of soybean into wheat. With funding from the Ohio Small Grains Marketing Program and the Michigan Wheat Program, we’ve conducted several wide-row wheat trials.

    How much is wheat yield reduced when planting in wide rows compared to narrow rows? In most instances, wheat yield is greater when grown in narrow row width (7.5-inch) compared to wide row width (15-inch). Yield reductions associated with wide row wheat production ranges from 0% to 15%. In wide-row wheat, we tend to see more head-bearing tillers per foot of row compared to narrow-row wheat. This suggests that under some conditions, increased tillering in wide-row wheat may compensate for lower initial plant population per unit area. The level of yield reduction associated with wide row wheat production varies among wheat varieties. Therefore, variety selection is important when growing wheat in wide rows. Annually, a wide row wheat variety test is performed at two locations in Ohio. Variety information for the Ohio Wheat Performance Test Wide Row Evaluation can be found at:       

    What is the ideal seeding rate for wide-row wheat?

    An on-farm trial was conducted at three locations in Fulton County during the 2013-2014 growing season and one location during the 2014-2015 growing season. The “standard practice” of wheat grown in narrow rows at 2.0 million seeds/acre was compared to wheat grown in wide rows at 1.0 and 1.5 million seeds/acre. Averaged across site-years, wheat grain yield was 81.7 bu/acre when grown in the standard practice of 7.5-inch row width at 2.0 million seeds/acre.  Compared to the standard practice, average yield across seeding rates was reduced by 15% when grown in 15-inch row width. When wheat was grown in 15-inch row width, there was no difference in yield between the 1.0 and 1.5 million seeds/acre seeding rates. This indicates that greater than 1.0 million seeds/acre may not be necessary to maximize yield of wheat grown in 15-inch row width.

    With fewer plants per acre in wide-row wheat production, can nitrogen application rate be reduced?

    No. Although fewer plants are recommended in wide-row wheat production (approximately 1.0 million seeds/acre) compared to narrow row wheat production, do not change nitrogen application rates.  Agronomic optimum nitrogen rates are the same regardless of row width.  

    Wide Wheat Row Management Tips:

    • Choose a variety that is high-yielding and resistant to major diseases such as powdery mildew, Septoria and Stagonospora blotches, and head scab.  See for the Ohio Wheat Performance Test Wide Row Evaluation.
    • Plant wheat as soon as possible after the Hessian fly-free date.
    • A seeding rate of approximately 1.0 million seeds/acre is recommended.
    • Do not change nitrogen application rates.
    • Weed control is very important in wide-row wheat production.
    • Changing row spacing will change the microclimate within the wheat canopy, and this could affect disease development. Scout fields for foliar diseases and use the scab forecasting system ( to determine whether disease risk is high enough to warrant a fungicide application.

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)
Anne Dorrance (State Specialist, Soybean Diseases)
Ed Lentz, CCA (Educator, Agriculture and Natural Resources)
Elizabeth Hawkins (Field Specialist, Agronomic Systems)
Eric Richer, CCA (Field Specialist, Farm Management)
Glen Arnold, CCA (Field Specialist, Manure Nutrient Management )
Greg LaBarge, CPAg/CCA (Field Specialist, Agronomic Systems)
Jason Hartschuh, CCA (Field Specialist, Dairy & Precision Livestock)
Kelley Tilmon (State Specialist, Field Crop Entomology)
Ken Ford (Educator, Agriculture and Natural Resources)
Laura Lindsey (State Specialist, Soybean and Small Grains)
Les Ober, CCA (Educator, Agriculture and Natural Resources)
Mark Badertscher (Educator, Agriculture and Natural Resources)
Peter Thomison (State Specialist, Corn Production)
Pierce Paul (State Specialist, Corn and Wheat Diseases)
Sam Custer (Educator, Agriculture and Natural Resources)
Ted Wiseman (Educator, Agriculture and Natural Resources)
Wayne Dellinger, CCA (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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