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Ohio State University Extension


C.O.R.N. Newsletter 2012-29

Dates Covered: 
September 4, 2012 - September 11, 2012
Harold Watters

Bean Leaf Beetle in Late Maturing Soybeans

With many soybean fields starting to yellow and mature, our concern needs to turn to late maturing fields that are, and will remain, green for the next few weeks.  As fields mature, bean leaf beetle adults will leave and look for soybean fields that are still green to continue their feeding prior to overwintering.  Because of very high numbers that can come into green fields, the soybeans remain susceptible to pod feeding.  Growers are urged to monitor any field that is still green for their presence and feeding activity.  Treatment is warranted if feeding injury is reaching 10-15% of the pods and beetles are still actively feeding.  Remember that if treatment becomes necessary, growers should note the preharvest interval on the insecticide label so that they can still harvest on time.  Late maturing fields could be those late planted, including those doubled or intercropped.  Special concern should include soybeans grown for seed or as food grade soybeans.

Southern Corn Rootworm in Soybean

We have received reports of large numbers of adult southern corn rootworms, also known as spotted cucumber beetles, in soybean fields.  Growers are concerned about these rootworms laying their eggs in soybeans and causing injury to first year corn next year.  At this time our belief is that there is NOT a need for concern.  The southern corn rootworm does not reportedly overwinter in Ohio, overwintering farther south of our state, and then, as adults move north.  Thus, there should be no threat to corn roots in Ohio from this insect.  Additionally, there is no known variant of the southern corn rootworm that is associated with laying its eggs in soybeans to become a corn pest the following year as with the western corn rootworm variant, or a variant whose eggs survive more than one year as with the northern corn rootworm variant.  Southern corn rootworm is at best a very minor corn pest in the Midwest, and not much attention is usually given to it.  However, we plan on discussing this insect and its presence in soybeans with colleagues during meetings over this coming fall and winter to see if there are any other thoughts on it.  If there is a concern, we will inform you through future C.O.R.N. newsletters.

Concerns about Aflatoxin in Ohio Corn

There have been a few reports of Aspergillus ear rot in corn in some parts of Ohio, causing producers to be concerned about possible grain contamination with aflatoxins. As I mentioned in my newsletter a few weeks ago (, ear rot development does not automatically mean that grain is contaminated with aflatoxins, but provides a good indication that the risk of contamination is high. So far this year I have had only one confirmed report of aflatoxin contamination in the state. The best way to determine whether you indeed have an aflatoxin problem is to scout fields for Aspergillus ear rot and then send samples to a lab for testing. Below is a list of steps one should take when sampling for ear rot, testing for aflatoxin, and handling suspect grain samples during shipment and storage.

1-     Scouting for Aspergillus ear rot: Walk fields and examine ears from multiple plants at multiple locations. The fact that weather conditions this year have been favorable for Aspergillus ear rot does not automatically mean that you have an ear rot problem. The risk is indeed high, but the level of infection and grain contamination usually varies from field to field, depending of soil type, hybrid susceptibility, and cropping practice. Check for Aspergillus ear rot by stripping back the husks and examining the ears of 80-100 plants from across the entire field for a yellow-green or gray-green mold.

2-     Sampling for aflatoxin:  Samples for aflatoxin testing could be collected directly from the field, truck, grain stream, or grain bin. However, regardless of where the sample is being collected, it is important to make sure that it is representative of the entire grain lot. By representative I mean it must be a sample that provides a reasonable estimate of the level of contamination of the entire grain lot and not just one section of the lot. Toxin contamination is never uniform throughout a grain lot, it is often found in hot spots. Therefore it is extremely important to pull multiple samples from every part of the lot. When sampling from the grain stream, collect samples at regular intervals. Pool and mix the individual samples into one composite sample from which about 5-10 lb. of grain is sent for testing.

3-     Sending samples for aflatoxin testing: Adequate handling of samples is an important part of the aflatoxin testing process. Samples should be dried to 12-14% moisture and shipped in cloth or paper package to minimize aflatoxin buildup during shipment and storage.

4-     Testing for aflatoxin: A) Blacklight or UV light test consists of visually inspecting the grain for the presence of greenish florescent particles under UV light. This test should only be used as an initial screen, since other particles in the sample may also glow, giving a false positive result. On the other hand, the absence of a fluorescent glow does not mean that the grain is not contaminated. B) Several commercial quick-test kits are available for aflatoxin testing. Unlike the blacklight test, these are specific for aflatoxin. However, several of these tests are only qualitative or semi quantitative, meaning that they tell you whether or not the grain is contaminated or whether the level of contamination is within a certain range, but do not provide precise estimates of the levels of contamination. C) Analytical laboratory tests, if done correctly by a certified lab, are by far the best for determining aflatoxin contamination. These tests are usually accurate and quantitative, and provide estimates of the exact level of contamination. Grain marketing decisions such as dockage and price discounts should be made based on results from analytical lab tests rather than blacklight or commercial quick tests.

5-     Storage: To minimize further mold development and toxin accumulation in storage, grain should be dried to 15% moisture shortly after harvest. Remember, the level of toxin will not decrease in storage, but could increase substantially if storage conditions are favorable for continued fungal growth and mold development. Aspergillus flavus, the aflatoxin fungus, grows best at 80-90oF and 18% moisture. Cleaning grain after harvest to remove fines may also contribute to reducing toxin buildup in storage, since broken and cracked kernels often favor the growth of A. flavus.

More information on aflatoxin testing and FDA thresholds are available at:

Here is what our neighbors in the Midwest are seeing and saying about aflatoxin in corn:




Corn ear abnormalities: “Tip dieback” and “zippering”

Drought and record high temperatures had a major impact on ear formation in Ohio this year. In some fields, severe drought resulted in plants in which ears were absent (“barren”) or severely reduced in size with a few scattered kernels (nubbin ears). Even in fields which received timely rains, corn ears with unfilled tips were common (no kernels evident on the last two or more inches of the ear tip). Several factors may cause this problem. The ovules at the tip of the ear are the last to be pollinated, and under stress conditions only a limited amount of pollen was available to germinate late emerging silks. Pollen shed may have been complete or nearly complete before the silks associated with the tip ovules emerged. As a result, no kernels formed at the ear tip. Severe drought stress resulted in slow growth of the silks that prevented them from emerging in time to receive pollen. Uneven soil conditions and plant development within fields may have magnified this problem. Pollen feeding and silk clipping by corn rootworm beetles and Japanese beetles also contribute to pollination problems resulting in poorly filled tips and ears.

Tip dieback

Incomplete ear fill may also be related to kernel abortion. If plant nutrients (sugars and proteins) are limited during the early stages of kernel development, then kernels at the tip of the ear may abort. Kernels at the tip of the ear are the last to be pollinated and cannot compete as effectively for nutrients as kernels formed earlier. Heat and drought (as well as other stress conditions, such as nitrogen deficiency, hail, and foliar disease damage) may cause a shortage of nutrients that lead to kernel abortion. Periods of cloudy weather following pollination, or the mutual shading from very high plant populations can also contribute to kernel abortion. Some agronomists and farmers characterize the kernel abortion that occurs at the end of the ear as “tip dieback”, “tip-back”, or “nosing or tipping back”, although poor pollination is also usually a factor affecting poor kernel set at the tip. Kernel abortion may be distinguished from poor pollination of tip kernels by color. Aborted kernels and ovules not fertilized will both appear dried up and shrunken; however aborted kernels often have a slight yellowish color.

Another ear development problem that’s getting attention due to drought stress is “zippering” in which corn ears exhibit missing kernel rows (often on the side of the cob away from the stalk that give sort of a zippering look on the ears”).  The zippering often extends most of the cob’s length. Zippering is often associated with a curvature of the cob, to such an extent that zipper ears are sometimes referred to as "banana ears". This ear deformation is caused by the absence of kernels on one side of the cob coupled with the continued development of kernels on the other side that "force" the cob to bend or curve.

Zippering is due to kernels that are poorly developed and/or ovules that have aborted and/or not pollinated along the length of the ear. Affected ears are often associated with corn plants which have experienced drought stress during early grain fill; cobs associated with the zippering are usually smaller than normal and poor tip fill is often present. Recent OSU studies indicate that some hybrids are much more susceptible to zippering than others and that zippering among such hybrids is more pronounced at higher seeding rates. In studies in which corn plants have been subjected to severe defoliation during the late silk and early blister stages, we’ve observed the resulting ears to show zippering, which suggests that a sudden reduction in photosynthate supply may be a factor. The zippering did not occur when plants were subject to similar defoliation at the milk or dough kernel development stage.

Zipper ears

What is difficult to explain about zippering is why poor pollination or kernel abortion occurs along one side of the ear rather than being localized at the tip of the ear and why this very distinct "missing row" pattern usually occurs on the outside of ears (the side of the ear away from the stalk. Possible explanations include the following: 1) silks attached to the kernels (associated with the missing row) were covered up by other silks and simply did not get pollinated or, more likely, were pollinated late and as a result were more prone to abortion; 2) differential corn rootworm beetle silk clipping and feeding, i.e. beetles are below the ear during daytime hours, preferentially clipping silks of kernels facing downward; 3) differential kernel growth rate on the ear. Under drought stress, silk emergence can be slower than pollen shed. Perhaps silks on the outside or underside of the ear emerge more slowly than those facing the stalk? As a result, they may be pollinated later or emerge after pollen shed is complete. The later pollinated kernels may be outcompeted for limited photosynthates by other kernels which are larger and further along in development, and thus more effective in competing for the limited supply of photosynthates (similar to the problem that occurs with kernel abortion that occurs at the tip of the ear - "tip dieback"). Based on a recent report indicating that the upper sides of corn ears are often warmer than lower sides, Dr. Bob Nielsen at Purdue University suggested that differential heating of ears around their circumference could be a factor contributing to the "zipper" pattern of kernel abortion. If upper sides of ears are often warmer than lower sides, it “…would certainly offer a possible explanation of the "zipper" pattern of kernel abortion in years where the crop experiences not only excessive heat but also drought stress during or shortly after pollination. In addition to delayed metabolic rates and restricted photosynthetic assimilates, the development rate of the cooler kernels would be slower and, thus, the kernels somewhat "younger" and more vulnerable to the effects of severe stress.”


Nielsen, R.L. 2011. The "Zipper" Pattern of Poor Kernel Set in Corn. Available at
URL:  (URL verified 9/3/12)

Thomison, P. and A. Geyer. 2007. Abnormal corn ears. Ohio State University Extension. ACE-1. available at (URL verified 9/3/12)

Five Important Management Steps to Profitable Wheat Production in Ohio

The 2012/2013 winter wheat season is fast approaching and as growers make preparations for planting, we would like to remind them of a few management decisions that are important for a successful crop. Nearly every farm in Ohio has a field or two that could benefit from planting wheat, if for no other reason than to help reduce problems associated with continuous planting of soybeans and corn. Consistent high yields can be achieved by following a few important management guidelines. Below are listed the most important management decisions that Ohio wheat producers need to make at fall planting time to produce a crop with satisfactory economic returns.

ONE. Select high-yielding varieties with high test weight, good straw strength and adequate disease resistance. Do not jeopardize your investment by planting anything but the best yielding varieties that also have resistance to the important diseases in your area.  Depending on your area of the state, you may need good resistance to powdery mildew, Stagonospora leaf blotch, and/or leaf rust. Avoid varieties with susceptibility to Fusarium head scab. Plant seed that has been properly cleaned to remove shriveled kernels and treated with a fungicide seed treatment to control seed-borne diseases. The 2012 Ohio Wheat Performance Test results can be found at (

TWO. Plant after the Hessian Fly Safe date for your county. This date varies between September 22 for northern counties and October 5 for the southern-most counties. Planting within the first 10 days after this date minimizes the risk of serious insect and disease problems including Hessian Fly, aphids carrying Barley Yellow Dwarf Virus, and several foliar diseases. Planting before this date has lowered yield by 7 to 20% in research trials due to disease and insect problems. On the other hand, planting late (generally after Oct 20 in northern Ohio) can reduce the number of primary tillers that develop in the fall and increases the risk of cold temperature injury. The Hessian Fly free dates can be found at (

THREE. Optimum seeding rates are between 1.2 and 1.6 million seeds per acre.  For drills with 7.5 inch row spacing, this is about 18 to 24 seeds per foot of row with normal sized seed. When wheat is planted on time, actual seeding rate has little effect on yield, but high seeding rates (above 30 seeds per foot of row) increase lodging. There is no evidence that more seed is better, it only costs more money. If planting is delayed to more than three weeks after the Fly-Free date, plant 24-26 seeds per foot of row which is 1.75 million seeds per acre.

FOUR. Planting depth is critical for tiller development and winter survival. Plant seed 1.5 inches deep and make sure planting depth is uniform across the field. No-till wheat into soybean stubble is ideal, but make sure the soybean residue is uniformly spread over the surface of the ground.  Shallow planting is the main cause of low tiller numbers and poor over-winter survival due to heaving and freezing injury. Remember, you can not compensate for a poor planting job by planting more seeds; it just costs more money.

FIVE. Apply 20 to 30 lb of actual nitrogen per acre at planting to promote fall tiller development.  A soil test should be completed to determine phosphorus and potassium needs. Wheat requires more phosphorus than corn or soybeans, and soil test levels should be maintained between 25 to 40 ppm for optimum production. If the soil test indicates less than 25 ppm, then apply 80 to 100 pounds of P2O5 at planting. Do not add any phosphorus if soil test levels are higher than 50 ppm. Soil potassium should be maintained at levels of 100, 120 and 140 ppm for soils with cation exchange capacities of 10, 20, or 30, respectively. If potassium levels are low, apply 100 pounds of K2O at planting. In Ohio, limed soils usually have adequate calcium, magnesium and sulfur for wheat. Soil pH should be between 6.3 and 7.0.

The key to a successful wheat crop is adequate and timely management. The above recommendations are guidelines that may be fine-tuned by you to fit your farming operation and soils. They also assume that you are planting wheat in fields that are adequately drained. You can review more details on these, and other, research-based wheat management recommendations on-line at

Burndown herbicides for no-tillage wheat

Herbicide options for burndown of existing weeds prior to planting of no-till wheat include glyphosate, Gramoxone, Sharpen, and dicamba.  Dicamba labels have the following restriction on preplant applications – “Allow 10 days between application and planting for each 0.25 lb ai/A used”.  A rate of 0.5 lb ai/A would therefore need to be applied at least 20 days before planting.  We do not know of any 2,4-D product labels that allow preplant application in wheat, and Liberty is not approved for this use either. 

The primary targets for a preplant burndown in wheat are the small, emerged winter annual weeds that can overwinter and have a negative effect on wheat the following spring.  This includes marestail (horseweed), chickweed, deadnettle, annual bluegrass, mustards, etc.  Herbicide treatments at this time can also have considerable activity on biennials (wild carrot, wild hemlock), dandelion, and Canada thistle, although herbicides are often more effective on these weeds later in the fall.  While glyphosate can adequately control small winter annual weeds, it should be combined with Sharpen or dicamba in fields with a history of marestail problems (or in fields downwind of a neighbor’s marestail nightmare).  Gramoxone should also effectively control small seedlings of marestail and other winter annuals.  Be sure to use the appropriate adjuvants with Sharpen or Gramoxone, and increase spray volume to 15 to 20 gpa to ensure adequate coverage.

There are several effective postemergence herbicide treatments for wheat that can be applied in November to control winter annual weeds, in fields where preplant burndown treatments are not used.  Effective postemergence treatments include Huskie or mixtures of dicamba with Peak, tribenuron (Express etc), or a tribenuron/thifensulfuron premix (Harmony Extra etc), among others.  Huskie may be the most effective fall postemergence treatment for control of marestail, where the marestail population is resistant to ALS inhibitors.  We discourage application of 2,4-D to emerged wheat in the fall due to the risk of injury and yield reduction.

Isaac wrap up, and what's coming for early September

Isaac behaved as forecast. A wide range of rainfall with most areas getting 1-2 inches with some as little at 0.10 inches and some as high as 4-6 inches.

The outlook for the first two full weeks of September calls for near to slightly above normal temperatures (daytime highs will be normal or a bit below normal due to more clouds and night time lows will be above normal due to more clouds and moisture). Normal highs are in the 70s and lows in the 50s.

Rainfall is forecast to turn above normal. Normal rainfall is a little over 1 inch for the first half of the month. Rainfall will average 1-2 inches for the first half of the month. Isolated totals will of course be higher and lower than these amounts. After spotty early week rains, some more scattered rain will move through about Thursday with the best chance by this weekend. Things will dry out some next week.

Importance of Lime

Lime is an important component of nutrient management when the soil pH drops below the optimum range for crop production. Proper soil pH is important for nutrient availability, nitrogen fixation, herbicide activity, and crop development. Lime will neutralize the acidity of the soil and provide calcium and magnesium. For most Ohio row crops, the optimum pH range is between 6.3 and 6.8.

A soil test will be required to determine the need for lime and the amount. The pH value on a routine soil analysis will show whether a soil is in the optimum range for a crop. However, if lime is needed, the buffer pH or lime test index will be used to determine the amount of lime. The buffer pH takes in account the buffering capacity of the soil, or the ability of the soil to hold cations. The more buffered a soil (more clay and organic matter), the more lime will be required to raise soil pH. However, these same highly buffered soils will also take longer for the soil pH to drop.

All liming materials neutralize soil acidity in the same manner, but they are not the same in quality. Quality refers to the purity, neutralizing ability, grind size and moisture content of a liming material. These factors are all considered in the Effective Neutralizing Power (ENP) value found on a lime analysis sheet (for a producer, the ENP is basically the only value needed from the analysis). The ENP value allows a producer to compare different lime sources and determine their real cost based on the quality of the material. The better the quality the closer ENP will be to 2000 pounds. Examples of using ENP to determine real costs and amount needed may be found at the following website:

Hi cal lime (low levels of magnesium) should be utilized if it is a less expensive product than dolomitic lime (mix of calcium and magnesium carbonate) and magnesium levels are not below 50 ppm on the soil test. The calcium-magnesium ratio is not a concern unless soil calcium levels are less than magnesium levels. This normally does not occur in Ohio. Also keep in mind that dolomitic lime generally contains more calcium than magnesium anyway. As long as the soil test levels have more calcium than magnesium, there is no such thing as a “too high of magnesium level” (keep in mind that magnesium is an important component of the chlorophyll molecule in leaves). There have been cases of magnesium soil test levels being too low, particularly in eastern and southern Ohio. If magnesium is needed, dolomitic lime is generally the least expensive source.

In summary, obtain a soil test, determine the need for lime, confirm adequate soil magnesium levels, and then use the ENP value to select the most cost-effective lime material. Most Ohio soils do not need lime every year. Soil testing every three to four years can determine the continuing lime requirements for your fields.

Fall herbicide applications – an integral part of marestail management

The basic information on fall herbicide treatments can be found in a number of C.O.R.N. articles from previous years, including the following:

“Fall herbicide treatments”

“The ABC’s of fall herbicide treatments”

“Should residual soybean herbicides be applied in the fall?”

“Fall herbicide treatments – focus on marestail management”

Fall herbicide treatments are an important component of marestail management programs.  The primary role of the fall treatment is to remove the marestail plants that emerge in late summer and fall, so that the spring herbicide treatments do not have to control plants that have overwintered.  Failure to do so results in a population of plants in spring that is tougher to control and needs to be treated earlier, which introduces variability in burndown effectiveness and means that residual herbicides may be applied earlier than is optimal.  Conversely, an effective fall treatment results in a weed free seedbed in early spring, and more flexibility in the spring burndown/residual treatment timing.  The treatments recommended in the aforementioned articles will provide effective control of emerged marestail.  Marestail plants are small in the fall, and easily controlled with 2,4-D. 

The major errors with fall treatments where marestail is a target are:

1) using glyphosate or ALS inhibitors alone; and

2) spending money on residual herbicides that is better spent in the spring. 

The application of Canopy/Cloak products in fall can provide substantial residual control into the following spring of marestail that are not yet ALS-resistant, and other weeds as well.  However, many marestail populations are ALS-resistant, and it’s important to save most of the residual herbicide for the spring application. Our research has consistently shown that other residual herbicides – including Valor, Authority, and metribuzin – provide little residual in the spring when applied in fall.  The utility of these herbicides comes from spring application.

Poster highlighting ear abnormalities available

This year many Ohio farmers will encounter abnormal corn ears in their fields as a result of the drought and high temperature extremes (Fig. 1). However, other ear abnormalities may also impact yield and grain quality adversely. We have prepared a poster highlighting ten abnormal corn ears with distinct symptoms and causes (here). The purpose of the poster is to help corn growers and agricultural professionals diagnose distinguishing features among various ear disorders. A reduced 11 x 14 inch version of the poster is available online at:

The OSU College of Food Agric. and Env. Sci. Communications & Technology section (contact information below) has 26 x 33 inch copies of the poster available for distribution. The poster is printed on plasticized coated paper for durability. Poster cost is $11.25 plus shipping.  Ask for “Abnormal Corn Ears” poster” ACE-1.

The Ohio State University, College of Food Agric. & Env. Sci. 

Communications and Technology
Media Distribution
216 Kottman Hall, 2021 Coffey Road
Columbus, OH 43210-1044

Order Online:
Phone 614-292-1607
Fax     614-292-1248

Plan to attend the Farm Science Review September 18, 19 & 20

The growing season started early for all us in 2012 and what a change from last year. The crew and the grounds are ready for Ohio State University’s annual fall farm show on the site of the Farm Science Review at the intersection of US 40 and SR 38 just north of London. Crops are dry here too, and as of today harvest demonstrations are planned – yield expectations are about 120 on corn and 40 for beans, but that is better than we expected.

Tickets are available now for the 2012 Farm Science Review – to be held on September 18, 19 & 20 north of London Ohio – All Extension offices in Ohio and many agricultural businesses have the tickets for sale at $5 each. Tickets at the gate are $8.

The Agronomic Crops Team will again be at the Review

We have added a number of field demonstration plots to the Farm Science Review exhibit area for this year. Highlights:

·      Corn origins, from Teosinte to quad stacks

·      Soybean origins including wild soya

·      Managing corn and soybeans for higher yield

·      Corn planted into 2011 cover crops, what can go wrong

·      “bio-energy” crops.

·      The topic of drought, ear molds, late season soybean insect pests and weed resistance management all will be there to discuss and observe.

Stop by and get a tour from an Agronomic Crops Team member as you make your way from the parking lot to the exhibit area. We are just outside Gate C in the Agronomic Crops Team Plot area. As I told one visitor last year, we are the free entertainment; you don’t even need a ticket to visit with us.

•    Plan ahead to see your top priorities:

•    Golf cart rules, new for 2012:

Ammonia Emissions Field Day, Reminder Register Now

Workshop and Field Day: Mitigating Ammonia Emissions from Poultry Facilities for FertilizersSeptember 26, 2012, Raymond, Ohio.

This workshop is organized to provide poultry  producers and professionals with a systematic approach to managing ammonia emissions in poultry production. The brochure and registration information is online at:

Northern Ohio Small Farm College

An eight week introductory short course for anyone wishing to learn how to create profitable alternatives for a small farm or a few acres.  This short course will teach participants how to set goals, plan, budget, and where to find resources to start a small farm enterprise or add to an existing agricultural business.

Location:  Wood County Extension Office, 639 Dunbridge Road, Suite 1, Bowling Green, Ohio

Dates:  Mondays, October 1 through November 19, 2012

Time:  6:30 – 9:00 pm

Costs: $125 plus $25 each additional family member

For registration information:

For more information contact: OSU Extension Wood County: , 639 Dunbridge Road, Suite 1, Bowling Green, Ohio 43402, Ph 419-354-9050.








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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.