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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter: 2014-25


    Developing corn ears
    Author(s): Peter Thomison

    Have recent below average temperatures adversely affected corn growth and yield potential? No, corn actually yields best with moderate temperatures (and adequate soil moisture). Temperatures that occur in Ohio in July and August (especially at night) are often warmer than optimum for corn. The ideal daytime temperatures for corn are about 80 to 86 degrees F (and higher if moisture is plentiful at all times). Although some believe that corn grows best when nights are hot, past research shows that warm temperatures adversely affect yield potential. While temperatures in the 40’s may impair photosynthesis, high night temperatures (in the 70s or 80s) result in wasteful respiration and a lower amount of dry matter accumulation in plants. With high night temperatures, more of the sugars produced by photosynthesis during the day are lost; less is available to fill developing kernels, thereby lowering potential grain yield. Research conducted at the University of the Illinois indicated that corn grown at night temperatures in the mid - 60s outyielded corn grown at temperatures in the mid- 80s. High night time temperatures result in faster heat unit (GDD) accumulation that can lead to earlier corn maturation, whereas cool night temperatures result in slower GDD accumulation that can lengthen grain filling and promote greater dry matter accumulation and grain yields. Cool temperatures may also slow the development of foliar diseases and insect problems.

    Average corn yields are generally much higher with irrigation in western states, which have low humidity and limited rainfall. While these areas are characterized by hot sunny days, night temperatures are often cooler than in the Eastern Corn Belt.  Low night temperatures during grain fill are associated with some of our highest corn yields in Ohio – 143, 158, and 174 bu/A in 1992, 2004, and 2009, respectively.

    So what’s the “downside” to these lower than average temperatures? Cooler temperatures (if they continue) could delay grain harvest and result in higher grain moisture.  Growers may want to consider this possibility when they estimate fuel costs for drying grain. Moreover, the cool, wet growing season of 2009 was associated with ear rots and mycotoxins. The corn harvest in 2009 was delayed by frequent rains which allowed molds to grow resulting in major mycotoxin problems for many farmers.



    Hoeft, R.G.,  E. D. Nafziger, R.R. Johnson, and S.R. Aldrich. 2000. Modern Corn and Soybean Production. MCSP Publications, Champaign, IL. [see “Climate and Corn” section]

    Nielsen, R.L. 2014. Cool Temperatures & Grain Yield: Déjà vu for Corn? Corny News Network, Purdue Univ. [On-Line]. Available at



    Not much has changed in the outlooks for the rest of summer into autumn and beyond.

    In June, temperatures were about 1F above normal while in July temperatures were about -3F to -5F leading to an overall cooler than normal summer as forecast.

    The trend will be for slightly cooler than normal temperatures to last through August but the departures will not be as great as August.

    Rainfall in August will likely be close to normal.

    For the latest 16-day rainfall you can visit the NWS Ohio River Forecast site at:

    Autumn and harvest season is still shaping up to be slightly cooler and wetter than normal but the freeze risk for first freeze looks like about normal as wetter soils will keep night time lows up some.


    WBC 2014 Trap Totals
    Author(s): Andy Michel

    As predicted, we saw a slight decrease in the number of western bean cutworms caught in our monitoring network.  However, this was only seen in northwestern Ohio.  Instead, counties in northeastern Ohio had a dramatic increase in the number of adults, probably due to several weather systems coming across the lake.  Therefore, we are still in the window of egg laying, especially in corn that has just tasseled.  The total numbers this year have been surprising, given the low numbers last year.  We would be interested to hear of any larvae found feeding on ears, which can be observed for the next month or so, before larvae drop to the ground to overwinter.


    Results of the 2014 wheat performance evaluation are available at:  Currently, report text is unavailable.  However, tables with yield and agronomic characteristics are available online.

              The purpose of the Ohio Wheat Performance Test is to evaluate wheat varieties, blends, brands, and breeding lines for yield, grain quality and other important performance characteristics. This information gives wheat producers comparative information for selecting the varieties best suited for their production system and market. Varieties differ in yield potential, winter hardiness, maturity, standability, disease and insect resistance, and other agronomic characteristics.  Depending on variety and test site, yields varied between 76.8 and 129.9 bushels per acre, and test weight ranged from 56.9 to 61.1 pounds per bushel. Selection should be based on performance from multiple test sites and years.

              The 2013-2014 growing season had unusual weather, but wheat yields were overall good.  In fall 2013, wet field conditions and later than usual soybean harvest delayed wheat planting. Above average temperatures in October allowed for excellent emergence and early growth.  The extended warm temperatures promoted tillering and most fields entered winter dormancy in good to excellent condition.  In January and February, many areas of Ohio experienced negative air temperatures.  Additionally, many areas experienced above average snowfall.  Wheat survival the following spring was good.  Cool spring temperatures slowed wheat growth and delayed green-up.  May and June temperatures were fairly cool which resulted in an extended grain fill period.  Harvest was later than normal due to delayed maturation and rainfall.  Lodging was greater than usual; however, grain yield was good.  High grain yield is partly due to the gradual maturation of the crop resulting in an extended grain fill period.

  5. CORN EAR ROTS: How to Tell Them Apart and Know the Risk

    Author(s): Pierce Paul

    Ear rots or molds are usually most problematic when cool, wet conditions occur during silking and early grain development, when the ears are most susceptible to fungal infection. Three main types of ear rot (Diplodia, Gibberella, and Fusarium) usually affect corn in Ohio, and these differ from each other in terms of the damage they cause (their symptoms), the toxins they produce, and the specific conditions under which they develop. So, a good way to determine whether we will have an ear rot problem this year is to know how they develop and under what type of weather  conditions. And the best way to tell the difference among the ear rots is to know the types of symptoms they produce.

    DIPLODIA EAR ROT - Wet weather from mid June through mid July initiates the development of spores and heavy rain showers just prior to tasseling deliver the spores to the susceptible parts of the plants. Continuous rain in July favors infection and disease development. Diplodia causes a thick white mass of mold to grow on the ear, usually initiating from the base of the ear and growing toward the ear tip. Eventually the white mold changes to a grayish-brown growth and infected kernels appear glued to the husk. Infected ears are usually lightweight and of poor nutritional value. When infections occur early, the entire ear may become moldy. When infections occur late, only a fine web of fungal growth appears on the kernels.

    GIBBERELLA EAR ROT. Like Diplodia ear rot, Gibberella ear rot is generally most severe when rain and wet weather occur during the 7 to 10 days after silking. The fungus enters the ear tips through the silk channel. Optimum temperatures for disease development are 65-70°F. Ears with visible white to pink mold covering the ear tip or more of the ears are characteristic symptoms of Gibberella ear rot.

    FUSARIUM EAR ROT. Fusarium ear rot is especially common in fields with bird or insect damage to the ears. Affected ears usually have infected kernels scattered over the ear among healthy-looking kernels or are confined to kernels that are damaged. The fungus appears as a white mold and infected kernels sometimes develop a brown discoloration with light colored streaks.

    With ear rot comes the additional concern of mycotoxin contamination. In addition to the physical damage caused by ear rots, some ear rot fungi produce mycotoxins that reduce the quality and value of the grain. There have been no reports of Diplodia producing mycotoxins under field conditions, however, Gibberella and Fusarium species are known toxin producers. Gibberella zeae (which causes Gibberella ear rot and stalk rot of corn and wheat scab) produces several different mycotoxins that are harmful to livestock. Vomitoxin is one of the most common mycotoxins found in Gibberella-infected kernels. Hogs are particularly sensitive to this toxin. Vomitoxin can cause feed refusal at concentrations in grain at around 1 ppm. Several different Fusarium species are involved with Fusarium ear rot. One common species produces a toxin called Fumonisin. Horses are particularly sensitive to Fumonisin, but cattle and sheep are relatively insensitive.

    So, these are the risk factors for ear rots:

    1. If your hybrid is susceptible to one or more ear rots, you may be at risk,
    2. If weather conditions were (are) cool and wet (due to high humidity, dew, and rainfall)  for an extended number of days (7-14) after pollination and in to early grain development, then you may be at risk,
    3. If you are planting corn- after-corn, then you may also be at risk,

    Hail injury V-10 to V-13 corn, Photo by Mark Badertscher, Extension Educator Hardin County
    Author(s): Peter Thomison

    The impact of hail damage is largely dependent on corn’s stage of development.  Hail affects yield primarily by reducing stands and defoliating plants. Most of the hail damage results from defoliation. Generally, the corn plant is little affected by hail prior to the 6 to 7 leaf stage because the growing point is at or below the soil surface and in the leaf whorl. However, once the growing point is elevated above the soil surface due to internode elongation, the plant grows rapidly and becomes increasingly vulnerable to hail damage with the tassel stage/pollen shedding stage (VT) being the most critical period.

    Leaf damage by hail often looks much worse than it really is, especially during the early-to-mid stages of vegetative growth. Shredded leaves and plants with broken midribs still have some capacity to contribute to plant growth. Plants not killed outright by hail usually show new growth within 3 to 5 days after injury occurs (i.e. if damage occurs prior to tasseling). For this reason, estimates of hail damage during vegetative development should be delayed several days to allow for this period of re-growth.

    The hail insurance adjustor's growth staging system counts leaves beyond the last visible collar to the uppermost leaf that is 40-50% exposed whose tip points downward - usually this results in a leaf stage that is numerically 2 leaves greater than the "leaf collar method" (e.g. a V11 plant according to the leaf collar method would probably correspond to a 13-leaf plant according to the hail adjustor's method).

    How do we estimate the potential yield loss from recent hail storms? Growth stages vary considerably among fields this year due to differences in location, planting date, etc. Moreover, within some corn fields, it’s not unusual to see corn differ by three or more growth stages because of differences in soil color and drainage. Although much of the corn crop in Ohio is at or beyond the tassel (VT) and silking stages (R1), in some areas of the state there was considerable acreage planted in early to mid-June. Some of this late planted corn was damaged by hail last week when plants were at the V10 to V13 stages of development (see pictures). What impact did the hail storms have on corn yield (if we assume stand loss from hail damage was minimal)? Based on estimates of the National Crop Insurance Association (see Table 1 below), at the 13-leaf  stage (or about V11) if 50% of the leaf tissue is destroyed by hail, a corn plant loses 10% of its grain yield potential; if 100% defoliation occurs, a corn plant loses 34% of its yield potential. The pictures suggest significant defoliation injury to plants – probably exceeding 50% but not 100% damage. If the damage had occurred at VT or R1 loss of potential yield would have been much greater (Table 1).

    Table 1. Percent yield loss in corn based on growth stage & defoliation

    (Adapted from NCIA Corn Loss Instructions, rev. 1984)






    Growth Stage*





    13-leaf (V11)





    15-leaf (V13)





    17-leaf (V15)





    Tassel (VT)/Silk (R1)





    *as determined using the hail adjustor’s leaf staging method; ** approximate V-stage within parentheses

    For more detailed information on evaluating hail injury in corn, consult 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, RL (Bob). 2008. Recovery from Hail Damage to Young Corn

    Corny News Network, Purdue Univ. [On-Line]. Available at

    Vorst, J.J. 1993. Assessing Hail Damage to Corn. Purdue Univ. Cooperative Ext. Service Publication NCH-1. [On-Line]. Available at


    hail damage to soybean field, photo by Mark Badertscher, Extension Educator Hardin County

    On July 27, Hardin County experienced hail that damaged soybean at the R3 growth stage (beginning pod).  The R1 (beginning bloom) to R5 (beginning seed fill) stages are the most sensitive to defoliation.  At 50% defoliation when soybeans are at the R3 growth stage, we expect a 9-18% reduction in yield.  (See table for expected yield losses due to defoliation at several growth stages.)

    Last year, we conducted a hail simulation trial at the Western Agricultural Research Station in South Charleston.  Hail was simulated (via weed whacker) on July 18, 2013 when soybeans were at the R3 growth stage.  Defoliation was 40-45%.  Soybean yield was 74 bu/ac without hail simulation and 62 bu/ac with hail simulation.  (Yes, this was a statistically significant yield reduction.) 

    Despite cool temperatures this year, soybeans are adding a 1-2 new trifoliates per week which should help the plant recover.  In last year’s trial, there was very limited evidence of defoliation 12 days after the simulated hail. 

     Soybean Hail Damage Study (poster)


    Author(s): Adam Shepard

    The Southwest Ohio Corn Growers Association & Fayette County Agronomy Committee’s annual field day and test plot demonstrations will take place on Tuesday, August 12, 2014.  The field day will be held from 9:30 a.m. to 3 p.m. at the Fayette County Demonstration Farm at 2770 State Route 38, in front of the Fayette County Airport.

    The public is invited to this free event to hear from expert speakers and attend the trade show.  Services offered to the community include health screenings by the Fayette County Health Department & Fayette County Memorial Hospital from 9 a.m. to Noon, skin damage screenings by The Ohio State University Extension Office of Fayette County, also from 9 a.m. to noon, and the Ohio Department of Agriculture: Clean Sweep Program pesticide collection from 9:30 a.m. to 2 p.m.

    The morning session will feature Dr. Peter Thomison of Ohio State speaking ondrought tolerant corn hybrids in Ohio, Greg LaBarge of Ohio State Extension, discussing Senate Bill 150 and the fertilizer certification update, Dr. Anne Dorrance of Ohio State will give an update on soybean diseases in Ohio, Tony Dobbels of Ohio State speaking on Palmer amaranth, and David Brandt of Brandt Farms, leading a plot tour and discussing cover crop management. Also the morning session will offer participants the opportunity to observe the latest in precision agriculture and environmental technology by attending one of the unmanned aerial vehicle sessions or by visiting the mobile solar unit display to see how capturing sunlight can help save on utility bills.

    Lunch is provided during the noon session.  Dr. Bruce McPheron, Vice President for Agricultural Administration & Dean, will give his thoughts on the 100-year anniversary of the Smith-Lever Act and the role he believes agriculture and Extension will play in the future. The Ohio Corn Growers Association (OCGA) Executive Director will give an update on the OCGA.  After lunch will be a drawing for two $500 gift certificates for Ohio Corn Grower Members.  Memberships for the OCGA will be available all day at the event check-in table.  See for more information regarding membership.

    For further questions regarding the Southwest Ohio Corn Growers & Fayette County Agronomy Field Day, contact the Fayette County Extension Office at 740-335-1150.  CCA Credits will be offered.


    Author(s): David Marrison

    Assessing soybean diseases and insect pressure can be difficult without proper training and experience. OSU Extension in Northeast Ohio is pleased to be offering aSoybean Disease & Insect Field Night on Monday, evening, August 11, 2014 in Trumbull County, Ohio.  Farmers and crop consultants are invited to attend a 2 hour in-field session with Dr. Anne Dorrance and Dr. Andy Michel. This field will be held from 6:00 to 8:00 p.m.

    During the field night, participants will have the opportunity to identify insects and diseases and discuss when spray applications should be made. Participants will learn more about: white mold, brown spot, frogeye leaf spot, soybean aphids, bean leaf beetle, brown marmorated stink bug, and soybean aphids.

    The field night will be held in a soybean field planted by W.I. Miller & Sons. This field is located on State Route 87 just east of Route 193 on the south side of the road in Gustavus Township.    The field is 0.4 mile east of Route 193 and 0.5 mile west of Stoddard-Hayes Road.  Look for the OSU Extension field night signs.   Please dress for the weather as the program will be held rain or shine.  Walking is required.  If special assistance is needed, please call in advance.  No pre-registration is required.

    OSU Extension would like to thank W.I. Miller & Sons for hosting this field night for producers.  More information about this program can be obtained by calling the Ashtabula County Extension office at 440-576-9008 or the Trumbull County Extension office at 330-638-6783.  Certified Crop Advisor Credits & Private and Commercial Pesticide Applicator Credits have been requested for this field night. No reservations are required for this field night.  A program flyer can be found at:


    Author(s): , Adam Shepard,

    The Ohio Department of Agriculture (ODA) is sponsoring three farm pesticide collection dates during August and September.  The pesticide collection and disposal service is free of charge, but only farm chemicals will be accepted.  Paint, antifreeze, solvents, and household or non-farm pesticides will not be accepted.

    Pesticide collections are sponsored by the department in conjunction with the U.S. Environmental Protection Agency.  This collection is for farm operations only and does not include dealers or distributors.   For more information or if planning to bring quantities of more than a pick-up truck, contact the Ohio Department of Agriculture at 614-728-6987.  Pesticide collection dates and locations are:

    ·         Fayette County: August 12  from 9:30 am to 2:00 pm at the Fayette County Airport, 2770 State Route 38 NE, Washington Court House, OH  43160

    ·         Wayne County: August 29 from 10:00 am to 2:00 pm  at the Kidron Livestock Auction, 4885 Kidron Rd, Apple Creek, OH  44606

    ·         Wood County: September 9 from 9:30 a.m. to 2:00 p.m. at the Wood County Junior Fair Building, 13800 W. Poe Road, Bowling Green, OH 44606

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.


Bruce Clevenger, CCA (Field Specialist, Farm Management)
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)
Les Ober, CCA (Educator, Agriculture and Natural Resources)
Nathan Douridas, CCA (Farm Science Review Farm Manager)
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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