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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2011-22

Dates Covered: 
July 12, 2011 - July 19, 2011
Amanda Douridas

Weather Outlook

The overall pattern is behaving much like was forecast this spring. Temperatures have been warmer than average from June into July. This pattern will continue for the rest of July and likely August too. Rainfall has shifted from wetter than average this spring to generally drier than average. The drier pattern began to form in middle June and has kicked in in July as expected. This will likely continue into August as well. However, the pattern is supportive for some rainfall so we do not see a pattern where it does not rain at all, but one where rainfall at or below normal but one that has at least some rainfall.


July 11-25 - Temperatures 3-5 degrees above normal and rainfall 0.5"-1" north to 1"-2" south on average. Normal is near 2". Isolated places of <0.25" and >2" can be expected in this pattern but most places will fall in the ranges given.


Our research shows typically in La Nina springs (which 2011 was), yields in Ohio for corn and wheat are below normal and soybeans near normal. It will be interesting to see this year's results.

Predicting leaf development in corn using accumulated heat units

When estimating yield losses in corn due to hail, frost, and other types of plant injury, it’s essential to establish the stage of plant growth at the time damage occurred. It’s also important to know corn stage of development in order to apply post-emergence chemicals effectively with minimum crop damage. Counting leaf collars to determine the vegetative stage is feasible until the lower leaves can no longer be identified. At about the V6 stage, increasing stalk and nodal growth combine to tear the smallest lower leaves from the plant. This results in degeneration and eventual loss of lower leaves which makes it difficult to locate the lower leaves (especially the first rounded leaf). When identification of specific leaf collars on plants is not possible how can the leaf stage of development of a field be estimated?

Given an understanding of corn leaf stage development and heat unit (growing degree day, GDD) calculation, a grower can estimate what leaf stage of development a particular field is at given its planting date and temperatures since planting. 

Corn leaf developmental rates may be characterized by two phases. Purdue research indicates that from VE to V10 (ten leaf collars), leaf emergence occurs approximately every 82 GDDs accumulated (Nielsen, 2008). From V10 to tasseling (VT) leaf collar emergence occurs more quickly at approximately one leaf every 50 GDDs accumulated. Recent Iowa State University findings (Abendroth et al., 2011) relating leaf appearance to GDD accumulation are similar – from VE to V10 a new collared leaf appears every 84 GDDs accumulated and from V11 to VT, each leaf appears at approximately every 56 GDD accumulated.

Example: (from Nielsen, 2008): A field was planted on April 28, but you do not know exactly when it emerged. Since planting, approximately 785 GDDs have accumulated. If you assume that the crop emerged in about 120 GDDs, then the estimated leaf stage for the crop would be about V8. This estimate is calculated by first subtracting 120 from 785 to account for the estimated thermal time to emergence, then dividing the result (665) by 82 (equal to V8.1). 

Growth-limiting stresses and conditions (soil moisture deficits, nutrient deficiencies, compaction, etc.) affect the accuracy of these predictions. Nevertheless, this method may be useful in timing when plants will reach an approximate stage of growth.


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. 2008. Use Thermal Time to Predict Leaf Stage Development in Corn. Corny News Network, Purdue Univ. [On-Line]. Available at

Uneven plant development in corn: Impact on yield

In many corn fields this year, it’s not unusual to see differences in plant growth stage and height within and between corn rows. Although some of the variability in plant height can be related to uneven emergence, it’s important to recognize that plant height is not a reliable indicator of plant growth stage in corn. In some fields that show variability in plant height, tall and short plants may actually be at fairly similar stages of growth based on leaf collars.

In areas of NW Ohio where limited rainfall has occurred since early June, the primary factor causing uneven plant development within fields is probably soil  moisture variability within the seeding depth zone; it’s affected both emergence and subsequent growth. Other factors contributing to the problem include poor seed to soil contact due to cloddy soils, sidewall compaction/smearing, seeding depth, residue distribution, etc.

What impact will variability in development have on crop yields? It’s been well documented that uneven emergence affects crop performance because competition from larger, early emerging plants decreases the yield from smaller, later emerging plants. According to one popular rule of thumb, if two neighboring plants differ by two or more leaves, the younger plant will almost always be barren or produce a nubbin ear at maturity. Several studies have been conducted to determine how later emerging plants impact yield within a field of normal emerging corn. Such research has usually involved delaying the planting of a certain percentage of corn plants within a field to simulate variable emergence. Research in Ontario indicated that when one of six (17%) plants was delayed in emergence by two leaves, overall yield was reduced 4 percent; when delayed by four leaves, 8 percent yield losses were observed. Plants neighboring late emerging plants only partially offset yield losses. Illinois and Wisconsin research considered the response of corn when 25, 50, or 75 percent of the plants were planted either 10 or 21 days after the original planting date. Overall, grain yields were reduced 6 to 7 percent by a delayed planting of 10 days regardless of the percentage of plants delayed. However, when planting was delayed 21 days, yields were reduced 10 percent when 25 percent of the plants were delayed, 20 percent when 50 percent were delayed, and 23 percent when 75 percent of the plants were delayed. In a Minnesota study, corn planted normally was compared to that where half of the seeds were planted either 7 or 14 days later. Normal plants had larger stalks, more tillers, longer ears, more ears, fewer barren plants, and more grain per plant than late plants. Yields were reduced more with a 14-day delay than with a 7-day delay. At lower populations differences between the variable stands were small; as yields increased at higher plant populations, the later plants caused greater yield reductions.


Elmore, R. and L. Abendroth. 2006. What's the yield effect of uneven corn heights? Iowa State University Integrated Crop Management Newsletter (on-line at

Determination of ear size in corn well underway

During the past two weeks corn has “exploded” in growth in many Ohio fields. Under favorable growing conditions corn plants can grow nearly three inches per day between V8 (i.e., the eight leaf collar stage) and V15.  However, there is considerable variability in corn development across the state, between neighboring fields, and within fields. Some of this variation can be attributed to planting date differences - much of the corn planted in mid-May or earlier is at or beyond V14-15; some of this corn is tasseling and silking (VT/R1), whereas corn planted in early to mid June is usually at V9 or later. The variation in growth and development is also related to differences in rainfall accumulation. In areas of Ohio (especially NW Ohio) which have received limited rainfall since early June, tremendous variation in plant growth exists within fields. In most fields, plants differing markedly in plant height may differ by only one or two leaf collars. However, where moisture stress is especially severe, corn plants vary in height by more than 12-15 in. and differ in growth stage by four or more leaf collars. What impact will these varying environmental conditions have on kernel numbers and ultimately grain yield?

As early as the V4/V5 stage, ear shoot initiation is completed and the tassel is initiated on the top of the growing point. Kernel row numbers per ear is established by V12 and perhaps as early as V8 (Nielsen, 2007). Kernel row numbers are usually less affected by environmental conditions than by genetic background. Corn hybrids characterized by "girthy" ears exhibit more kernel rows (about 18 or 20 rows) than hybrids with long tapering ears (about 14 or 16 rows). Determination of kernels per row (ear length) is usually complete by V15 stage and maybe as early as V12 (Nielsen, 2007).  Unlike kernel rows per ear, kernels per row can be strongly influenced by environmental conditions. Kernels per row (ear length) can be adversely impacted by severe drought stress in the two weeks prior to pollination. Many of our late planted corn fields experiencing severe stress from a shortage of soil moisture have yet to reach V12. If these fields receive timely rains in the near future (between V12 and V17), loss of kernels per row on developing ears may be minimal and impact on potential yield limit


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. 2007. Ear Size Determination in Corn. Corny News Network, Purdue Univ. [online] [URL accessed 78/3/09].

Effects of wind lodging on corn performance

Effects of wind lodging on corn performance

Strong winds and heavy rains associated with severe thunderstorms can lodge or knock corn plants over, especially if the nodal root system is not fully developed. Hot, dry weather conditions and soil compaction may inhibit nodal root formation and predispose plants to wind injury. The shallow root systems associated with some of our late planted corn this year may be more vulnerable to wind lodging. Prospects for recovery of “downed corn” are usually good, especially when the injury occurs early before the mid-late vegetative stages (V13-VT).

Strong winds can pull corn roots part way out of the soil. The problem is more pronounced when soils are saturated by heavy rains accompanying winds. If root lodging occurs before grain fill, plants usually recover at least partly by "kneeing up." This response results in the characteristic gooseneck bend in the lower stalk with brace roots providing above ground support. If this stalk bending takes place before pollination, there may be little effect on yield. When lodging occurs later in the season, some yield decrease due to partial loss of root activity and reduced light interception may occur. If root lodging occurs shortly before or during pollen shed and pollination, it may interfere with effective fertilization thereby reducing kernel set. Several university studies have been performed to assess the impact of wind lodging on corn growth and grain yield.

In a University of Wisconsin study, root lodging was simulated by saturating soil with water and manually pushing corn plants over at the base, perpendicular to row direction. Wind damage was simulated at various vegetative stages through silking (V10 to R1). Compared to hand harvested grain yields of control plants, grain yield decreased by 2 to 6%, 5 to 15% and 13 to 31% when the lodging occurred at early (V10-V12), mid (V13-V15) and late (V17-R1) stages, respectively.

Iowa State University researchers forced V10 corn to “root lodge” at a 45 degree angle in plots with and without rootworms. Grain yield of root lodged corn without rootworms yielded 11 and 40 percent less than the control in the two years of the study while root lodged corn with rootworms yielded 12 and 28 percent of the control. Years were a major factor affecting the yield response. The ISU researchers concluded that “root lodging was more detrimental to biomass accumulation and grain yield than corn rootworm injury caused by larval feeding.” In another ISU study that evaluated natural root lodging, root lodged plants intercepted 28 percent less light than plants that were not root lodged.

Root lodging can be directly related to severe feeding by rootworm larvae. However, Bt rootworm resistance alone will not prevent root lodging. Hybrids differ in their ability to resist root lodging. Moreover, a hybrid may exhibit outstanding stalk lodging resistance but may be very susceptible to root lodging.

Carter, P.R. and K.D. Hudelson. 1988. Influence of simulated wind lodging on corn growth and grain yield. J. Production Agriculture. 1:295-299.

Elmore, R. 2005.Mid-to-late season lodging. Iowa State University Integrated Crop Management Newsletter IC-494(21)161-162. (

Remain vigilant for western bean cutworm

Numbers of western bean cutworm adults continued to increase over the week. We are now over 200 moths for the entire state (see new map at  Corn remains at risk for western bean cutworm egg deposition and infestation.  Egg scouting should begin by the end of this week. 

Bean Leaf Beetles Showing Up in Early Planted Fields

Over the past week we have started seeing first generation bean leaf beetle adults along with their typical feeding injury to new soybean leaves in early planted soybean fields.  As we discussed in the June 1, 2011-16 issue of this C.O.R.N. newsletter, these early planted fields acted as trap crops for the overwintered bean leaf beetle.  These fields saw much higher numbers of beetles than normal.  In that article, we offered a warning that these fields might end up seeing even higher numbers of first generation adult beetles in July, much higher numbers than usually seen. 

Growers who observed large numbers of overwintered beetles in any early planted field should plan on checking those fields closely during July. Although bean leaf beetles do not usually cause significant defoliation during July, we have experienced significant feeding injury in the top of the canopy as the beetles fed on young, expanding leaves in similar years with considerable spring rainfall that delayed planting.  Because soybeans do not seem to be putting on large amounts of leaf area at this time, this injury can quickly become significant.

The 2011 Wheat Scab Field Survey: Fungicide Treatment at Flowering and Variety Resistance Played a Major Role

Wheat harvest continues this week in parts of central and northern Ohio, and the numbers so far suggest that on average, this year’s crop is decent, despite disease and weather-related problems in some areas. Some fields suffered more than others did and some did far better than expected, but on average, yields are in the 60s and 70s, and test weights are in the upper 50s and lower 60s. At the extremes, some fields did poorly, with yields in the 30s, while others did very well, with more than 100 bu/ac. In terms of grain quality, vomitoxin levels are also relatively low, being below 5 ppm in the majority of the harvested fields, with the odd field having 7 to 9 ppm. These numbers are much lower than last year’s numbers, which was the most severe scab and vomitoxin problem Ohio has had in over 10 years.       

This year, the average scab incidence in fields not treated with a fungicide was 12.4%, and over 41% of these fields had more than 10% incidence. That makes 2011 the third highest year for wheat scab since 2002. In 2010, the overall average incidence was 19.5%, and 2004 had very similar levels of disease as 2011, with an average of 12.5%. Average incidence of all non-treated fields within each county surveyed ranged from 1.4% to 31.1%, while averages for individual fields ranged from 0 to 44.9% incidence. Higher incidence levels tended to occur in two main clusters of counties within the state, the southwest and the central to mid-northwest. However, there were a few fields in all parts of the state (southern, central, and northern) that had greater than 25% incidence.

Overall, fields planted to varieties with moderate levels of resistance to scab and/or treated with a fungicide had lower disease levels than those planted to susceptible or moderately susceptible variety and/or not treated with a fungicide. Here “treatment with a fungicide” means that a triazole fungicide, like Prosoro or Caramba, was applied at or near flowering, specifically for the reduction of wheat scab. Incidence in fields treated with a fungicide ranged from 0 to 22.2%, with an average of 6.0%. Moderately resistant varieties had lower incidence (5.9%) than susceptible and moderately susceptible varieties (8.7%). In addition, moderately resistant varieties treated with a fungicide had the lowest overall average level of scab (4%). Similarly, fields of susceptible varieties treated with a fungicide had an overall average incidence of 7.4% compared to those that were not treated, which had the highest average of 11.3%.

Of the fields treated with a fungicide, timing was important. Fields treated at flowering had a 50.5% reduction in scab, while those treated a few days too early or too late had a 15.7% reduction in scab, compared to the average level in the unsprayed fields surveyed within the county. At four farms in four different counties, untreated strips were left in fungicide-treated fields. At those four locations, scab levels were 30, 58, 67, and 89% lower in the treated section than in the untreated strips; showing very clear results of the effectiveness of fungicides when applied at the right time.

Wheat scab and vomitoxin continue to be the biggest threats to profitable production of high-yielding, high-quality wheat in Ohio. However, today, we have better and more effective tools than we did 10 years ago - the scab risk assessment system, better fungicides, and more resistant varieties.  Results for 2010 and 2011 show that selecting varieties that are moderately resistant, planting wheat after soybean (which the majority of growers in Ohio are doing), along with a well timed fungicide application is the most effective integrated approach for minimizing yield and quality losses due to scab.

We would like to thank all of the wheat producers who allowed us on their land to complete the survey, and the Agricultural and Natural Resources Extension Educators for their participation with scouting for disease and collecting information about fields.

Manure Science Review Coming Aug. 16

DEGRAFF, Ohio -- Ohio's annual Manure Science Review, featuring new and better ways to manage farm manure and wastewater, takes place in the state's west on Aug. 16.

Speakers from Ohio agencies, the farming community and The Ohio State University highlight the program. Both morning presentations and afternoon field demonstrations are part of it.

Organizers say the event has a double focus: to put waste to good use -- to fertilize crops, cut disposal costs and save farmers money -- and keep water supplies safe.

New technologies and alternative methods are some of the topics, with an emphasis on reducing runoff risk and nutrient loss. Of note are sessions on separating dairy solids and on using those solids as alternative bedding for cattle.

The program takes place from 9 a.m.-4 p.m. at the Winner Family Farm, 4317 State Route 47 West, in DeGraff in Logan County.

Registration costs $30 by Aug. 8, $35 afterward and at the door, with members of the Midwest Professional Nutrient Applicators Association receiving a $5 discount. A continental breakfast, lunch and all materials are included.

Download the registration form at, or call 330-202-3533 to have a copy sent to you in the mail. Included with the registration form are the day's schedule, directions, and the full list of topics and speakers.

Among the speakers:

  • Alan Winner, owner of the host farm, a 400-cow dairy that separates its solids for greater efficiency;
  • Tom Noyes, Wesley Haun and Amanda Meddles of Ohio State University Extension;
  • Jocelyn Henderson and Terry Mescher of the Ohio Department of Natural Resources (ODNR);
  • Frank Gibbs of the U.S. Department of Agriculture (USDA);
  • Christine Pence of the Ohio Department of Agriculture (ODA); and
  • Steve Searson of the Logan Soil and Water Conservation District.

Participants are eligible for 5.5 hours of continuing education credit under ODA's Certified Livestock Manager training program; 4.5 hours of Soil and Water Management credit in the Ohio Certified Crop Advisor (CCA) Program; 1 hour of Nutrient Management credit, also in the CCA program; and 5.5 Professional Development Hours for Professional Engineers.

Sponsoring the event are OSU Extension, Ohio State's Ohio Agricultural Research and Development Center, the Ohio Livestock Coalition, Ohio's Soil and Water Conservation Districts, ODA, USDA's Natural Resources Conservation Service, and ODNR.


Western Agronomy Day note, register by next Monday

The OSU Extension Agronomic Crops Team and OARDC Western Ag Research Station personnel present an agronomic crop research tour at the Western Agricultural Research Station on July 20th from 9AM to 3PM.

Pre-registration required - $20 per person – and please register by Monday July 18th.

To register contact Harold Watters, at the OSU Extension Office Champaign County, 1512 South US Hwy 68, Suite B100, Urbana OH 43078, 937 484-1526, Registration and agenda are available here:




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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.