CFAES Give Today
Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2013-15

Dates Covered: 
May 28, 2013 - June 4, 2013
Debbie Brown

NOAA End-of-May Weather Forecast

The pattern change we talked about last week has occurred but it appears the axis of heavier rain will not shift quite as far northwest as we thought last week. Last week it looked like the rain axis would be from Iowa to Michigan. Now it looks to be from southeast Iowa to Illinois to southern lower Michigan and northern Indiana and northwest Ohio. It is always the details that count.

What does this mean for Ohio? This means it will not get drier. For many this spells good growing conditions though some flooded fields could develop in northern and western sections for a short time this coming weekend.

The week of May 28 will feature much above normal temperatures and normal to above normal rainfall. Except in the far north, rainfall will be limited until late week allowing for any late planting to be completed. Temperatures will average 5-10 degrees above normal this week. It will also be a humid week. Rainfall will increase by the first weekend in June. Rainfall will average 1-2 inches with some places reaching 3+.

For the week of June 3...temperatures will retreat to near normal to slightly above normal and rainfall will back off to normal or slightly below normal.

Even though we had a very chilly March, April and May have turned out to be slightly warmer than normal and slightly drier than normal in the east and slightly wetter than normal in western sections of the state. Temperatures since April 1 are actually averaging 1-2 degrees above normal (just seems not as warm after the record warm 2012) across the state and rainfall is average within about an inch of normal in most places. For what we call normal, we really can't get much more normal in Ohio than this.

Keep up on the latest 2 week rainfall outlooks at the National Weather Service Ohio River Forecast Center link:

Normal on this link's graphic is about 2 inches.

Overall, the outlooks for 2013 we made in 2012 are working out very well.

The Risk for Head Scab Still Low but Could Change Later in the Week

Since last Friday, May 24, conditions have been unseasonably cold across the state, with temperatures ranging from low-30s to mid-60s. Rainfall has been spotty. Such low temperatures and infrequent rainfall are unfavorable for most wheat diseases, including head scab. However, it rained yesterday and is raining today in parts of northern Ohio where wheat is now going through the flowering growth stage, and more rain is in the forecast for later in the week. Temperatures will also increase over the next seven days, with highs in the upper-70s and mid-80s.

While most of our wheat would have flowered by the time it warms up later in the week, there is considerable variation in crop development in some areas that could still put some late-flowering fields at risk for scab. Moreover, the cool conditions we have had over the last week could extend the flowering window of our crop beyond the 2-3 days that is typical under warmer conditions. This could also put some fields at risk for scab. Today’s low-risk prediction on the scab forecasting website ( is based on conditions over the last seven days and does not include today’s warmer, wetter weather conditions. This prediction could change later in the week as warmer, wetter, scab-favorable conditions continue to develop. Producers with wheat flowering this week should continue to check the prediction system and consider applying Prosaro or Caramba if the risk for scab increases.          

Is My Wheat at Heading or Flowering Frost Damaged?

Unseasonably cold temperatures over the Memorial Day weekend have some producers concerned about frost damage to their wheat crop. Some are even thinking about abandoning their wheat fields under the assumption that all is lost. Indeed, temperatures were as low as 30-35F in some areas and a few frost-damaged spikes are beginning to show up in some fields; however, is the problem severe and widespread enough to justify abandoning your crop? Before you make a decision, here are a few things to consider:

1-  Your concerns may be justified since wheat is most sensitive to frost damage during the heading and flowering growth stages, since freezing temperatures at these stages may lead to sterility. However, if pollination has already occurred, your crop may be safe since, as the developing grain is less sensitive to cold temperatures. You can tell by opening a few florets at several locations across the field and examining the grain. The presence of healthy, greenish-white, developing grain is a good sign. Injured kernels are usually shriveled and whitish-gray in color.

2-  Did it get cold enough for long enough? Did temperatures drop below 30F for two or more hours? At the current growth stage, frost damage tends to be most severe when flowering-heads are exposed to temperatures of 30F or below for at least two hours.

3-  Heads with extruded anthers does not necessarily mean that your crop is still at the sensitive flowering growth state. Anthers may still be seen hanging from the heads during early grain fill. So, double check your growth stage. Remember, wheat is less sensitive to frost at the early dough stage than at the flowering stage.               

Asiatic Garden Beetle in Corn

Asiatic Garden Beetle in Corn



Last spring at this time, we mentioned a new corn pest that had appeared in extreme northern Ohio:  grubs of the Asiatic garden beetle (  This pest had been found as a newer corn pest in northeast Indiana and southwest Michigan around 2006-2008, always in sandier soils and following soybeans, both conditions which were met in Ohio last year.  Our concern was that this grub is considered very aggressive in its feeding habits, and thus, is much more damaging than most other grubs. 

Grubs of this species are smaller than other grubs likely to be found, such as true white grubs and Japanese beetle grubs.  The main characteristic that can be used to identify them are the enlarged maxillary palps on the side of their mouthparts. 

 Of concern right now is that stand losses from this grub have been found in corn fields in Tuscarawas County, south of Canton, OH, much farther south than we expected to ever find them.  The problem fields are in sandy soils in a lower river bottom area.  We would recommend growers throughout the state check corn in sandy soils, particularly paying attention to fields in river bottom areas where sandy soils are often found. 

If grubs are located, please contact us at, or else send them to us via your extension educator.  Place them in a container with moist soil for shipping.  Because we would like to hear of any stand reductions by any and all grubs, please collect any grubs that are present so we can correctly identify them.  But we especially need to determine other areas of the state where the Asiatic garden beetle is causing stand losses to corn.  At the present time, similar to other grub problems, there is not a rescue treatment available, and the only action would be replanting if necessary.  Remember that most of the grubs should be pupating shortly.

Corn "Leafing Out" Underground

Recent weather and seedbed conditions may have created emergence problems resulting in corn seedlings leafing out underground. Seedlings exhibiting this abnormal emergence (note images of samples we have received) may have a twisted appearance because internal leaves start expanding before the seeding has elongated. “Corkscrewed” mesocotyl/coleoptile development may occur when the coleoptile encounters resistance (like soil crusting or a dense soil surface) as the mesocotyl elongates. Several factors (or combination of factors) may be responsible for this abnormal growth. These factors may be characterized as environmental, chemical, or mechanical. Environmental conditions associated with underground leafing include light penetration, cold soils, or heavy rains soon after planting. When plants unfurl below the soil surface, they usually turn yellow and die.

 Thomison corn leafing out2

In a cloddy field where soil coverage of seed is poor and irregular, sunlight can reach the germinating seedling and induce leaf emergence beneath the soil surface. Also, heavy rains after planting can cause a hard crust, which makes emergence of small seedlings very difficult. As a result, bending and twisting of the seedling below the crusted layer often occurs. Planting the seed too deep has also been associated with premature unfurling of the corn.

Certain herbicides, such as cell growth inhibitors like acetochlor, and various premixes that contain their active ingredients can show similar symptoms (i.e. twisting, abnormal growth) when excessive rates are applied pre-emergence. Besides excessive rates, improperly closed seed furrows can allow the pre-emergence herbicide to come in direct contact with the seed. However, this year many of the Ohio reports of corn leafing out underground are occurring in fields where herbicides have not yet been applied.

In a 2012 article concerning corn emergence problems (, Dr. Bob Nielsen at Purdue University notes that cold soils and/or wide fluctuations in soil temperatures throughout the day during the emergence process may be a major contributing factor for the development of corkscrewed mesocotyl. Although the range in temperatures that trigger such corkscrewed mesocotyl development are not documented, during May this year we experienced wide diurnal fluctuations in soil temperatures. Moreover, Dr. Nielsen points out that dry soil conditions (which were not uncommon in many areas) would be more prone than wetter soils to wide swings in daily soil temperatures.

 Thomison corn leafing out3

Corn seedlings that exhibit abnormal unfurling symptoms during emergence will be unable to penetrate any but the loosest soil even if the crust is broken mechanically or softened by rain. Prompt treatment with a rotary hoe, weeder, spiketooth harrow, or cultipacker may help break the crust and improve emergence. However, even when used carefully, these salvage operations can cause some damage to seedlings which are emerging normally. To minimize poor seedling emergence due to unfurling below the soil surface, watch for cloddy seedbeds, open seed furrows, and crusting surface soils after rains.


Nielsen, R.L. 2012. Corkscrewed Mesocotyls & Failed Corn Emergence

Corny News Network, Purdue Univ. Online at [URL accessed May 28, 2012]

Corn Replanting Considerations

So far, there is little evidence that most corn plantings in Ohio have been jeopardized by the frosts and cool temperatures we experienced during the past week. However, in some localized areas there may be fields where cold soil temperatures resulted in loss of stand. Farmers confronted with poor stands due to freezing temperatures, as well as other problems that affect corn stands, may be considering replanting their fields.

The corn plant is generally little affected by frosts prior to the V6 stage because the growing point is at or below the soil surface and in the leaf whorl. Plants not killed outright by freezing injury usually show new growth within 5 days after injury occurs. Warmer temperatures forecast for the remainder of this week should promote such regrowth.

Replant decisions in corn should be based on strong evidence that the returns to replanting will not only cover replant costs but also net enough to make it worth the effort. Don’t make a final assessment on the extent of damage and stand loss too quickly. The following are some guidelines to consider when making a replant decision.

If the crop damage assessment indicates that a replant decision is called for, some specific information will be needed, including:

          Original target plant population/Intended plant stand

          Plant stand after damage

          Uniformity of plant stand after damage

          Original planting date

          Possible replanting date

          Likely replanting pest control and seed costs

To estimate after‑damage plant population per acre, count the number of viable plants in a length of row that equals 1/1000 of an acre and multiply by 1000. Make several counts in different rows in different parts of the field. Six to eight counts per 20 acres should be sufficient. Table 4-12 in the OSU Agronomy Guide shows row lengths required to equal 1/1000 acre when corn is planted at various row widths.

A major consideration in making a replant decision is the potential yield at the new planting date and possibly different planting rate; this can vary depending on the hybrid used, soil fertility and moisture availability. Table 4-15 in the OSU Agronomy Guide is a chart developed by Dr. Emerson Nafziger at the University of Illinois that show effects of planting date and plant population on final grain yield for the central Corn Belt. Dr. Bob Nielsen has modified this table to provide estimates of potential yield losses for planting dates in early June (on-line at

Grain yields for varying dates and populations in both tables are expressed as a percentage of the yield obtained at the optimum planting date and population.

Here’s how these tables might be used to arrive at a replant decision (Table 4-15 from the OSU Agronomy Guide will be used in this example). Let’s assume that a farmer planted on May 9 at a seeding rate sufficient to attain a harvest population of 30,000 plants per acre. The farmer determined on May 28 that his stand was reduced to 15,000 plants per acre as a result of saturated soil conditions and ponding. According to Table 4-15, the expected yield for the existing stand would be 79% of the optimum. If the corn crop was planted the next day on May 29 and produced a full stand of 30,000 plants per acre, the expected yield would be 81% of the optimum. The difference expected from replanting is 81 minus 79, or 2 percentage points. At a yield level of 175 bushels per acre, this increase would amount to about 3.5 bu per acre.

It’s also important to note plant distribution within the row. Remember that values in replant charts like Table 4-15 from the OSU Agronomy Guide are based on a uniform distribution of plants within the row. Add a 5% yield loss penalty if the field assessment reveals several gaps of 4‑6 feet within rows and a 2% penalty for gaps of 1‑3 feet. Yield loss due to stand reduction results not only from the outright loss of plants but also from an uneven distribution of the remaining ones. The more numerous and longer the gaps between plants within the row, the greater the yield reduction. It’s also important to consider the condition of the existing corn.

When making the replant decision, seed and pest control costs must not be overlooked. Depending on the seed company and the cause of stand loss, expense for seed can range from none to full cost. As for the correct hybrid maturity to use in a late planting situation, continue to use adapted hybrids switching to early/mid maturities, if necessary, depending on your location in Ohio.

You also need to review herbicide and insecticide programs under late‑planting conditions. For instance, it may be necessary to reapply herbicides, especially if deep tillage is used. However, try to avoid such tillage depending instead on postemergence chemicals or cultivation for weed control. Concerning insect control, if soil insecticides were applied in the row at initial planting, check insecticide label restrictions before re‑application. Also remember that later May and June planting dates generally increase the possibility of damage from European corn borer (ECB) so planting ECB Bt hybrids is often beneficial.

The cost of replanting will differ depending on the need for tillage and chemical application. The cost and availability of acceptable seed will also be considerations. These factors must be weighed against expected replanting yield gains. If after considering all the factors there is still doubt as to whether or not a field should be replanted, you will perhaps be correct more often if the field is left as is.

Current Insect Issues on Field Crops

Current Insect Issues on Field Crops

Cereal Leaf Beetle on Wheat – We received a number of reports last week of wheat fields with large numbers of cereal leaf beetle larvae starting to feed on the flag leaves, the most important leaf on a wheat plant in terms of yield.  Although these reports were from widespread areas across Ohio, growers across the state might want to check their wheat and even oat fields to make sure this insect is not reaching economic levels.  The threshold needed for treatment is a single larva per main stem or wheat head.  This is a lower threshold from what was used a few years ago, when it was set on two larvae per main stem.  A fact sheet on cereal leaf beetle is at while a list of possible insecticides to use is at  For any organic producers, remember that Entrust, a spinosad product, is labeled for cereal leaf beetle control. 

Alfalfa Weevil – Many growers have made their first cutting of alfalfa because of large numbers of alfalfa weevil in taller alfalfa.  Recommendations do call for cutting alfalfa early if sufficiently tall rather than making an insecticide application.  Of importance is that if larvae survive the cutting and lack of food for a few days, they might still be alive when regrowth begins and possibly start feeding on the new growth.  Growers who cut early for alfalfa weevil purposes should scout their fields for possible feeding of the new growth.  If feeding is occurring, an insecticide application may be necessary.

Black Cutworm – Cutworm problems have become common in the Midwest including Ohio.  This is a reminder that growers should scout potential cutworm problem fields, especially those fields that are no-till with weed growth this past spring.  The corn is very small at this time because of late planting, and thus, much more susceptible to larval injury.

Save the Dates: Upcoming Activities!!


Tuesday, August 6th

Fulton County Fairgrounds in Wauseon, Ohio

Morning sessions:  Agronomics: What Research has Taught Us about Precision Planter Tech and Variable Rate Seeding, What are All the Planter Possibilities, How Do I Manage All of My Data 

 Aternoon:  Live planter demos with John Deere, Case, Kinze and Horsh participating. 

The event is free and producers only need to RSVP for lunch count at or call 419-337-9210."


August 21, 2013

OARDC Western Agriculture Research Station 

7721 S. Charleston Pike South Charleston, OH 45368

Morning and afternoon sessions and field demonstrations will address different seeding methods and timing, new forage varieties, forage fertility, high yield management and cover crops as forages! More details to come.


Thursday, August 29th, 6:00PM

Jackson Agricultural Research Station
019 Standpipe Rd., Jackson, OH

/Supper at 5p; Program 6p-~8:30p

Keys to High Quality Large Bale Silage, Making a High Quality Fall Forage Seeding, Heifer Selection Tools/Strategies, Latest Heifer Development Research

Registration: $5 per person includes supper.
Deadline August 26th; pre-registration required.



Archive Issue Contributors: 
Archive Issue Authors: 

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.