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Ohio State University Extension


C.O.R.N. Newsletter 2007-26

Dates Covered: 
August 13, 2007 - August 21, 2007
Todd Mangen

Soybean Growers Should be Aware of Bees When Spraying Insecticides

Authors: Ron Hammond, Greg LaBarge, Bruce Eisley

Growers and custom applicators should be aware of the need to protect bees when spraying around soybeans for soybean aphid, twospotted spider mites, or other soybean insects (or any crop or insect pest for that matter). Remember that numerous insecticides have a caution statement on their label about spraying around bees and blooming crops. The typical statement is: “This product is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees are actively visiting the treatment area”.

The Ohio Department of Agriculture addresses this concern under Regulatory Divisions & Programs, Plant Industry Division, Pesticide Regulations, Law and Statues, Plant Industry 901:5.
901:5-11-02 restrictions

(B) No person shall:

(15) Apply or cause to be applied any pesticide that is required to carry a special warning on its label indicating that it is toxic to honey bees, over an area of one-half acre or more in which the crop-plant is in flower unless the owner or caretaker of any apiary located within one-half mile of the treatment site has been notified by the person no less than twenty-four hours in advance of the intended treatment; provided the apiary is registered and identified as required by section <>909.02 of the Revised Code of Ohio, and that the apiary has been posted with the name and telephone number of the owner or responsible caretaker.

(16) Apply pesticides which are hazardous to honey bees at times when pollinating insects are actively working in the target area; however, application of calyx sprays on fruits and other similar applications may be made.

We continue to advise that growers and applicators maintain good communications with bee keepers near their fields to prevent and limit unintended problems. A listing of registered apiaries can be obtained from the Ohio Department of Agriculture. The website is The list can be requested via e-mail to the address

Below are some specific recommendations for environmental and pesticide factors that will lessen the potential for injury to bees.

1) Drift of pesticide not only can injury non-target plants but bees or other insects located within the canopy of non-target plants. Follow all precautions related to drift such as wind speed, direction identifying risk potential of neighboring crops. Recently we have seen more fields with filter strips or other conservation areas along borders. Plants in these border areas may be in bloom and harboring foraging bees. Drift or spray overlay has the potential to cause injury to bees and should be considered in pesticide applications.

2) Timing of application can limit bee injury. Applications in the evening or early morning are generally best. Bees are less active at these times of the day. Other times when the blooms are less attractive and lower bee activity are acceptable as well.

3) Formulations of pesticides will make an impact on toxicity. Dust and wettable powders are more toxic than emulsifiable concentrates. Ultra low volume applications versus a regular application are generally more toxic. No repellents can be added to tank mixes that will keep bees away from treated areas.

4) Toxicity of pesticides can differ. Most pesticide have been tested with bees in laboratory settings. Keep in mind there can be differences in field results versus laboratory results due to environmental factors as well as the sensitivity difference in populations of bees.

Should Glyphosate be Applied to Roundup Ready Soybeans?

Authors: Mark Loux

Now that soybeans are being sprayed for aphids and spider mites and some for nutrient deficiencies, questions are coming in about adding glyphosate to the spray mixture. If weeds have emerged after the last glyphosate application and they are not too numerous or will not drastically affect harvesting, then it probably is not necessary to apply glyphosate to control the weeds. If weeds have recovered from previous glyphosate applications and the maximum in-season rate (2.25 lb ae/A) of glyphosate has not been met, then applying glyphosate may reduce seed production of those surviving plants and reduce future glyphosate control issues. This strategy will, however, ensure survival of those plants with the highest level of resistance, if this is why the plants are surviving.

One major issue with applying glyphosate late in the season to Roundup Ready soybeans is the risk for injury. We have observed that soybeans treated in late July or later in the summer are more likely to be injured by glyphosate, especially when under stress. Labels for Monsanto brand glyphosate products state that they can be applied to soybeans through the R2 growth stage (flowering), but not after the R3 growth stage begins. The R3 growth stage begins when one of the uppermost four nodes with a fully developed leaf has a pod that is at least 3/16 inch long. Application of glyphosate to soybeans that have started the R3 stage is not supported by the labels (i.e. not legal). We assume that the labels for most other glyphosate products contain similar guidelines, but we have not conducted a thorough search of labels to verify whether this is the case. Nearly all of the April and May planted soybeans are beyond this growth stage at this time.

The activity of glyphosate can be reduced when applied in mixtures with manganese. This reduction in activity is of greater concern when trying to control weeds that have escaped prior herbicide treatment and under drought conditions. Control of velvetleaf can be especially problematic when using these mixtures. Our best suggestion is to apply glyphosate and manganese separately when trying to clean up weedy fields this late in the season. Ideally, the glyphosate is applied first, followed by an application of manganese at least one day later. When it’s impossible to avoid mixing glyphosate and managanese, follow these guidelines:

1. Use an EDTA-chelated form of manganese, which has less potential to reduce glyphosate’s activity in comparison with other forms of manganese.
2. Include ammonium sulfate in the spray mixture at the rate of 17 lbs/100 gallons. Add the ammonium sulfate to the spray tank first, followed by the manganese, followed by the glyphosate.
3. Use the highest glyphosate rate that can legally be applied, based on the amount used in previous postemergence applications (see comments on rate earlier in article).

"Beer Can" Ears Appearing in Corn Fields

Authors: Peter Thomison

I have received several reports in recent weeks of “beer can” ears, an abnormal condition in which corn ear length is markedly shortened. This ear abnormality has also been referred to as ear stunting, or “blunt ear”, or "pinched ear" syndrome.

Two key visual symptoms associated with ear stunting are ears that are much shorter than normal and a considerable section of the ear tip that has not produced kernels. This latter symptom appears to be related to poor pollination, perhaps the result of tight husks preventing and/or delaying normal silk emergence. These husks tightly cover stunted ears and may not provide adequate space for silks to emerge normally. “Beer can” ear problems are often associated with multiple ear shoots per node. Several nodes of the affected plant may exhibit stunted ears and multiple ears per node.
Corn plants with stunted ears generally appear healthy with normal husk formation and growth. However, husks may appear somewhat pointed, probably because husks were more tightly wrapped around the much smaller ear enclosed. At harvest, plants with stunted ears often turn purple due to an accumulation of sugars in the leaf and stalk tissue. Ear stunting is often localized within fields (e.g. head rows and border rows or patches within fields) with only a small percentage of plants (<1-5%) affected.

Little is known concerning possible causes of this abnormal ear development. The problem may be related to a low temperature stress or shock during ear development between the 5-leaf collar stage and 12-leaf collar stage. In 1992, a year during which corn ear stunting was widely observed across the Corn Belt, the only common factor shared by fields exhibiting ear stunting problems seemed to be low temperature (down to near freezing) in late June during ear size determination. The localized occurrence of beer can ears within a field supports speculation that some stress may be impacting ear development of a limited number of plants, which are at a highly sensitive growth stage.
No consistent relationships between soil fertility levels, herbicide programs or corn diseases is evident. Some have suggested micronutrient deficiencies associated with high pH effects which may play a role. Hybrids also appear to differ in susceptibility to the problem.

For more about this ear abnormality and other ear development anomalies showing up this year, check out the following online articles:

Nafziger, E. 2007. Unexpected problems of corn ear development. The Bulletin. University of Illinois. No. 20 Article 9/August 10, 2007. (

Nielsen, R.L. 'Beer Can' Ear Syndrome – 2001. Corny News Network, Purdue Univ. [On-Line] (

Nielsen, R.L. 2007. Multiple Ears on the Same Shank. Corny News Network, Purdue Univ. [On-Line] (

Cobalt Insecticide Labeled on Soybeans

Authors: Ron Hammond, Bruce Eisley

A new insecticide, Cobalt, has recently been registered on soybeans for control of various insects, including soybean aphid, and various other crops including alfalfa, corn, and wheat to name a few. This compound, by Dow AgroSciences, is a mixture of chlorpyrifos (the same material found in Lorsban, Nufos, and Yuma) and gamma-cyhalothrin (the same materials found in the pyrethroid Proaxis). Growers should read the label for rates and various restrictions. Cobalt is a restricted material.

Sentinel Plot Report: August 2007

Authors: Anne Dorrance

Leaves from Ohio’s sentinel plots continue to be collected and ALL ARE NEGATIVE for soybean rust. Mites, frogeye leaf spot, downy mildew and brown spot are the winners in this order. The presence of mites across the state indicates that producers should be very careful about applying fungicides at this time. Fungicide applications can cause a flare-up of mites.

From the southern states, Texas, Oklahoma, Arkansas, Louisiana as well as Mississippi continue to add counties as more soybean rust is found in the south. Many of their soybeans are approaching R5 and R6, so the rust is coming in very late this year due to the drought earlier in the season. What this means for Ohio is that we are at very, very low risk of rust impacting our April, May and June planted soybeans for the current season.

Controlling Burcucumber in Corn

As burcucumber in some parts of the state is making its way over the top of corn and with concerns about these plants eventually pulling the corn plants down, the question has been posed as too what can be done. At this time of the season, a preharvest application of 2,4-D can be used to potentially reduce the spread of the vines and seed production. Burcucumber will not be controlled by the 2,4-D, however, the hope is to suppress the plants enough to not pull the corn over and reduce the viability of seeds being produced. Apply the maximum rate of 2,4-D [2 pints/A – (1.0 lb ai/A)] to achieve the greatest activity after corn has reached the hard dough or denting stage. The ester formulation should provide the greatest suppression, however, it will have the greatest likelihood to volatilize compared to an amine formulation.

Once corn has reached the black-layer stage of development (physiological maturity) then paraquat can be applied as a preharvest aid. After black-layer and after the corn grain is below 35% moisture, glyphosate can be applied as a preharvest aid.

In the future, be sure to scout corn fields with a history of burcucumber when a more effective postemergence herbicide can be applied. A preemergence followed by a late postemergence herbicide application usually provides the greatest control of burcucumber.

Estimating Preharvest Silage Yields

Authors: Peter Thomison

Although rainfall during recent weeks has helped many drought stressed corn fields, some areas are still experiencing significant rainfall deficits. In a recent C.O.R.N. article (July 30, 2007 - August 6, 2007), a widely used procedures for estimating corn grain yields prior to harvest was explained. Grain producers who are considering the costs of harvesting drought stressed corn as grain vs. silage need to assess yield potential in order to evaluate grain and silage marketing options. Two “quick and dirty” methods for evaluating yield of corn silage are as follows:

Grain yield method for estimating silage yield
For moisture-stressed corn, about 1 ton of silage per acre can be obtained for each 5 bushels of grain per acre. For example, if you expect a grain yield of 50 bushels per acre, you will get about 10 tons/acre of 30% dry matter silage (3 tons/acre dry matter yield). For corn yielding more than 100 bushels per acre, about 1 ton of silage per acre can be expected for each 6 to 7 bushels of grain per acre. For example, corn yielding 125 bushels of grain per acre, corn silage yields will be 18 to 20 tons per acre at 30% dry matter (5 to 6 tons per acre dry matter yield).

Plant height method for estimating silage yield
If little or no grain is expected, a rough estimate of yield can be made assuming that 1 ton of 30% dry matter silage can be obtained for each foot of plant height (excluding the tassel). For example, corn at 3 to 4 feet will produce about 3 to 4 tons per acre of silage at 30% dry matter (about 1 ton per acre of dry matter).

Adapted from: Lauer, Joe. 2006. Concerns about Drought as Corn Pollination Begins
University of Wisconsin. Field Crops 28.493 – 42.

For additional information check:
Weiss, Bill. 2007. Pricing Drought-Stressed Corn Silage C.O.R.N. article (July 30, 2007 - August 6, 2007) []

Pricing Corn Silage in 2007

Authors: Bill Weiss, Dianne Shoemaker

Pricing from the seller’s (corn grower’s) point of view:
“Production costs (excluding harvesting) are the same whether corn is harvested as grain or silage. I want to maximize return per acre.”

1. Estimate income less harvest costs if crop was sold for grain:
Estimate grain yield (bu./acre), multiply by price of corn if sold (from the field) as grain, and then subtract harvesting and any storage costs to get gross post-harvest return per acre. This is usually the minimum price ($/acre) for which you would be willing to sell standing corn. Harvest costs would include combining, hauling grain, drying, storage and any other marketing costs incurred for the sale of the crop as grain. For example, if estimated corn grain yield is 100 bu/acre, out of the field price of corn grain is $3.60 and grain harvest costs are $39/acre, then income less harvest costs would be $330 per acre.

Example: (100 bu./ac. x $3.60/bu.) - $39/ac. = $321/acre

2. Estimate silage yield per acre.
A. For severely drought-stressed corn that has little if any corn grain, measure height of several plants (not including the tassel). Calculate average height (in feet) and multiply by 0.9 to estimate tons of corn silage (35% dry matter) per acre. For example average height is 6.5 ft x 0.9 = 5.9 tons of corn silage per acre.

Note: This is not an appropriate method of estimating yield of normal or even mildly drought-stressed corn.

B. For mild to moderately drought-stressed corn, estimate grain yield (bu./acre) and divide that number by a value between 5 and 8. Five is for fields with moderate drought-stress (grain yield substantially depressed) and 8 is for fields with little drought stress (yields essentially equal to normal). If uncertain, 6 to 7 is a good compromise.

Example: Grain yield is estimated at 100 bu./acre (mild to moderate stress) divided by 6.5 = 15.4 tons of corn silage (35% dry matter) per acre.

3. Estimate price of corn silage needed to match return when selling grain.
From step 1 above, return via grain was $321/acre and estimated silage yield (step 2B) is 15.4 tons. $321/acre divided by 15.4 tons/acre = $20.84/ton of corn plants standing in field (assumed harvested at 35% dry matter). This price should be increased a bit to cover the value of the organic matter that will not be returned to the field.

Buyer’s (livestock producer’s) Point of View.
“I don’t care what I feed my cows as long as the diet provides the right nutrients. I want to maximize return per cow.”

Determine what other feed, or more likely, feeds can be used to provide the nutrients provided by corn silage (remember, cows require specific nutrients, they do not require specific feeds). Your nutritionist can formulate several diets with different feeds and determine feed costs for the various diets. An alternate method is to estimate the value of corn silage based on the value of the nutrients it provides. Corn silage provides net energy, effective fiber, and crude protein to dairy cows and those three nutrients comprise the bulk of the economic value of corn silage to a dairy producer.

Using a statistical technique, the economic value of those three nutrients can be estimated based on the prices and nutrient composition of all (or most) of the feeds available in a market. The method is complicated, but the calculated values appropriate for central Ohio at a specific point in time are available in the Buckeye Dairy News (

Both methods require knowledge of the nutrient composition of the corn silage or corn plants (this is usually not known) and the future price of nutrients and feeds (also not known). When you do not have complete information, averages often are the best available option. Assuming average nutrient composition of drought-stressed corn silage and using the dollar value of nutrients averaged over the past year, corn silage (35% dry matter) has a maximum value to a dairy farmer of $47 to $61/ton (average $54/ton). A range is given because of the uncertainty associated with using averages and with the statistical method used to calculate the value of the nutrients. For normal (not drought stressed) corn silage, the maximum value would be in the $58 to $60 range based on this year’s nutrient prices.

The $54/ton (+/- $7/ton) price is the maximum price a dairy farmer should be willing to pay for corn silage when it is fed to the cow. In other words, all costs and losses associated with silage making have been paid. A dairy farmer should not pay more than about $54/ton because other feeds could replace corn silage at a lower cost.

To arrive at a price to pay for a standing crop based on the $54/ton (+/- $7/ton) nutrient value, the costs for harvesting, storing and associated shrink and risk must be deducted.

The average cost of storing corn silage is about $4/ton (35% DM) and since the dairy farmer usually owns the storage system this cost is deducted. During good fermentation approximately 10% of the dry matter put into a silo is lost (carbon dioxide, seepage, etc.) and this cost, sometimes referred to as shrink, also needs to be deducted when buying corn plants, rather than already-fermented silage.
Maximum feed value of corn silage when fed to a cow: $54/ton
Cost of storage - $4/ton
Cost of shrink - $5/ton
Maximum value of chopped corn plants when put in silo $45/ton

If you are purchasing standing corn and the dairy farmer is paying for chopping, that cost must also be deducted:
Maximum value of chopped corn plants when put in silo $45/ton
Cost of chopping, hauling, fill - $6/ton
Maximum price of standing corn plants (before risk) $39/ton

When a dairy farmer purchases either standing corn or chopped corn plants, he is assuming it will have the correct dry matter, ferment properly and turn into good corn silage. This usually happens, but not always. Drought-stressed corn carries the additional risk of having high nitrates. The risk of a poor fermentation and high nitrates must be considered and the price of either standing corn or chopped corn plants should be discounted. Negotiations between the grower and dairy farmer ultimately determines this discount.

Maximum price of standing corn plants $39/ton
Risk adjustment (negotiated) -Negotiated
Maximum price of standing corn plants (after risk adjustment) Negotiated

Determining Actual Selling/Purchase Price
In the example above, the grower must sell standing corn plants at $22.50/ton (the $21.40 calculated in Step 3 was increased to cover the value of organic matter) to make the same return as he would if he sold the crop as corn grain. The standing corn plants are worth something less than $39/ton to a dairy farmer. Therefore the negotiation range would be between $22.50/ton and $39/ton. On average, things average out which means the selling/buying price for standing corn in this example would be about $30/ton.

Morrow County Corn/Soybean Field Day

The Morrow County corn/soybean field day is scheduled for August 21st. The event will be held rain or shine at the Headwaters Outdoor Education Center which is located just north of the County jail. (One mile northeast of Mt. Gilead off U.S.Rt. 42) The event will feature speakers on agronomy and marketing. Most of the event will be inside.

The first speaker will begin at 10 A.M. and the event will conclude at 2 P.M.. Topics and speakers include:
* Nutrient Deficiencies and Nitrogen on Corn - Dr. Robert Mullen, OSU Fertility Specialist
* Managing for Resistant Weeds - Dr. Mark Loux, OSU Weed Specialist
* Low Linolenic Soybeans - Ms. Mandy Heth, QUALISOY Representative
* County Plot Update - Steve Ruhl, ANR Educator
* Ethanol Industry in Ohio Update - Tadd Nicholson, Ohio Corn Growers
* Energy and Crop Outlook - Dr. Matt Roberts, OSU Economist

There will be a lunch provided and reservations are requested. Please call the Extension Office at 419-947-1070 by August 20th. The event is free and open to the public. Walk-ins will be charged $5.00 per person. Please bring lawn chairs.

The field day is being hosted by the OSU Extension Office in Morrow County and the Morrow SWCD. The hosts would like to acknowledge the following sponsors: Crop Production Services, Central Ohio Farmers Co-op, Seed Consultants, QUALISOY, and the Morrow County Commissioners

Archive Issue Contributors: 

State Specialists: Anne Dorrance and Dennis Mills (Plant Pathology), Ron Hammond and Bruce Eisley (Entomology), Mark Loux and Jeff Stachler (Weed Science), Peter Thomison (Corn Production), Bill Weiss and Dianne Shoemaker (Animal Science). Extension Educators: Steve Foster (Darke), Roger Bender (Shelby), Howard Siegrist (Licking), Harold Watters (Champaign), Todd Mangen (Mercer), Jonah Johnson (Clark), Gary Wilson (Hancock), Alan Sundermeier (Wood), Glen Arnold (Putnam), Mike Gastier (Huron), Steve Bartels (Butler), Greg Labarge (Fulton), Ed Lentz (Seneca), Mark Koenig (Sandusky/Ottawa), Steve Ruhl (Morrow/Marion), Steve Prochaska (Crawford), Wesley Haun (Logan).

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.