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Ohio State University Extension


C.O.R.N. Newsletter 2005-30

Dates Covered: 
September 12, 2005 - September 19, 2005
Andy Kleinschmidt

Bt Corn in Ohio

Authors: Bruce Eisley, Ron Hammond

There are several Bt events available for use in Ohio corn. The first ones that came on the market contained Bt for European corn borer and are marketed as YieldGard Corn Borer (YGCB) and Herculex 1. The most recent event to come to market is the one that controls rootworm and is being marketed as YieldGard Rootworm (YGRW). We also have seen in the past year hybrids that have both YGCB and YGRW being placed in the same hybrid and marketed as YieldGard Plus. Over the years we have tested some of these events to see where, when and if they are needed in Ohio. Following is a short report on our findings.

Bt for Corn Borer

We have tested various hybrids with Bt corn borer technology for eight out of the last nine years for efficacy against European corn borer and yield, especially hybrids containing the YGCB event. The plots were planted at the Western Ag Research Station and Northwest Ag Research Station in randomized, replicated trials. In addition to trials at the stations, we also had on-farm strip trials for four years using the same hybrids. The first thing we want to point out is that the technology works very well because it was difficult to find any ECB damage in YGCB hybrids. However, we found that when we planted on time, late April to early May, we seldom saw significant differences in yield between YGCB hybrids and their isolines. Lack of yield differences was also observed with the on-farm strip trials. However, when we planted plots in late May at either Western or Northwest we did see a 6 bushel increase in yield with the YGCB hybrids. Based on these findings, we suggest that the Bt event for ECB will be most beneficial when used in later plantings. Data from these trials can be found online at:

Bt for Rootworm

This technology has only been on the market for a couple of years but we do know that it does a good job in controlling corn rootworm in Ohio corn. We are trying to determine where and when we should use this technology in Ohio corn production. There are a couple of conditions in Ohio corn production that would benefit from this new technology. Corn following corn has the potential threat from corn rootworm larval injury and we normally suggest that some kind of rootworm treatment be applied when planting, including YGRW. The other condition that could benefit from YGRW is if the western corn rootworm variant is a problem in fields in Ohio.

Extension Educators have been monitoring yellow sticky traps in soybean fields throughout Ohio this past summer. Early reports indicate that the all but one field has very few beetle counts. Based on these numbers, the western corn rootworm variant should not be a problem in these fields if corn is planted next year in these soybean fields. The variant may be a problem in other fields in Ohio, but without trap counts we cannot make a prediction. But all indications so far this summer suggest that the variant should not be a widespread problem. We would suggest that YGRW hybrids be used only on corn following corn unless there is a potential problem with the variant next year based on sampling or other observations.

Bt for European Corn Borer & Corn Rootworm

This newest technology is being marketed as YieldGard Plus. Plants with this technology have the events for both corn borer and rootworm. Where to use this technology is even more difficult to determine since it has both events. Our suggestion is that you follow the guidelines that we have outlined for Bt corn borer and Bt rootworm, and only use YieldGard Plus if you feel that both insect pests might be a problem.

Protect Grain Quality and Profits through Storage Bin Preparation

As the harvest season fast approaches, producers need to prepare their grain handling equipment and storage facilities now to handle, store and protect their grain quality and profits. Grain storage never improves grain quality, thus one needs to do everything possible to reduce the impacts of storing grain to limit the extent to which grain quality and profits will deteriorate. Away to approach protecting grain quality and profits is by following the precepts of the S.L.A.M. Pre/Post Harvest IPM Strategy: sanitation, loading, aeration, and monitoring.

Sanitation is a major proactive, first step in preparing for grain harvest and storage. Sanitation includes the following actions: 1) Remove vegetation and maintain a weed-free grain handling facility. Removing vegetation will eliminate refuge for rodents and insects that could consume and damage grain. It will make clean-up of spilled grain easier. And it may make it safer to work around the facility (i.e. trip hazards will not be hidden by tall weeds). 2) Clean all grain handling equipment (combines, trucks, wagons, conveyors, augers, etc.) to avoid contaminating new grain with moldy, insect infested grain left from previous use. 3) Remove all grain spills as soon as possible. This will reduce attraction of insects, rodents and birds. 4) Clean storage structures, inside and out. 5) Disinfect storage structures, inside and out. 6) Clean grain before binning by using screens, scalpers, or perforated auger tubes. And, 7) seal unloading auger, auger tube opening, and side door openings.

Empty bin treatments may be required to disinfect some bins. Insecticides registered for empty bin treatments for bins to be used for corn or soybeans include the following: Tempo SC Ultra (Beta-cyfluthrin), Storcide II (chlorpyrifos-methyl and deltamethrin), DIACON II ((S)-methoprene), and Dryacide, Insecto, or Protect-It (silicon dioxide or diatomaceous earth). Fumigants registered for empty bin fumigation for sub-floor aeration areas include: Chlor-O-Pic (chloropicrin) and Fumiphos, Fumitoxin, Phosfume, Phostoxin, Weevil-cide and others (aluminum phosphide).

The benefits of these actions include: 1) The chance of mold and insect development is reduced. 2) The need for a grain protectant may be avoided. 3) Broken grain, foreign materials, weed seeds and fines are kept out of the bin that will improve the effectiveness of aeration. And, 4) sealed openings prevent insect entry and cold air loss.

How the grain is handled during the loading process will also influence how well it will store. The following steps can improve grain storage life: 1) expand the use of combination and slow drying methods. 2) Minimize grain transfer operations by optimizing handling and storage systems. 3) Operate augers and elevators at capacity and at the slowest possible speeds. 4) Store grain in aerated structures. 5) Use a spreader to fill the bin. 5) Core the fines from the center of the grain. And, 6) level peaked grain once the bin is filled.

The benefits of these actions include: 1) Reduction of stress cracks and brittleness from overdrying of grain. 2) Airflow through clean grain is higher and more uniform. And, 3) clean grain has a greater storability.

Aeration is an important tool in successfully storing grain. The aeration system should be used to uniformly cool the grain mass to 30-35F by mid-December. One needs to be sure that the cooling front is moved completely through the grain mass before shutting down. For proper aeration, adequate exhaust vents need to be in place to avoid condensation on the inside walls and roof. Once the grain mass is cooled to the desired temperature, fans should be sealed to prevent unwanted air migration through the mass that could result in early grain mass warm-up. Cold grain has a longer storage life than warm grain. Aeration can also help equalize non-uniform moisture contents from high-temperature drying.

Finally, monitoring the grain mass during the storage time is essential. Monitoring the grain mass is the only way to be sure all your measures for protecting your grain quality and profits have been and will be successful. Monitoring should start soon after aeration is begun to assure that cooling fronts have completed exited the grain mass. Regular monitoring after that time will allow one to detect developing problems before they get out of hand. Touch and smell the grain to detect hot spots and mold development. Insect probe traps can be used to detect insect activities. And regular inspects will also result in detecting leaks through which rain and snow may enter.

Following the S.L.A.M. steps can result in a very successful storage season and preserve one’s peace of mind. One final note, grain can be a very dangerous material to work around because of potential entrapment, thus work in pairs when ever possible. Don’t get caught alone! Next week, more on stored grain insecticides, changes in labels and registrations, and what’s available for different grains.

Fall Herbicide Treatments - How They Fit Into Overall Weed Management Plans: Part II

Authors: Mark Loux, Anthony Dobbels

In last week’s article we discussed the merits of residual herbicides, and questioned whether they were most effectively used in fall or spring (or both). There appear to be two basic approaches that producers take with regard to fall and in-crop applications, and the choice of approach and the nature of the weed population dictates somewhat when residual herbicides can be used.

Approach 1. This approach should be used only in Roundup Ready soybeans. The herbicide program consists of a fall treatment, followed by a postemergence glyphosate application in the Roundup Ready soybeans. This approach will be most effective when the soybeans are planted in a timely manner, followed by average or above-average rate of growth and development. Key points on this approach:
- there is no spring preplant burndown treatment, so the use of a residual herbicide in the fall is recommended, to control weeds as long as possible into the spring and build the appropriate application window for the postemergence application.
- In OSU research with fall applications, chlorimuron-containing herbicides (CanopyXL, EX) have typically provided the longest period of residual activity into next year’s soybeans. A rough ranking of fall-applied herbicides for the length of residual control: CanopyEX > Gangster > Scepter > Valor = Sencor = Python. Higher rates of these herbicides usually improves the length of residual control into next growing season, however, the slight increase in residual control for some of these herbicides will not be offset by the increase in cost. A minimum of 1.1 oz/A of Canopy EX or 2.5 oz/A of Canopy XL is necessary for optimizing dandelion control and providing some level of residual control into the following spring. Higher rates certainly provide longer residual activity into next growing season, but will not improve control of ALS resistant species nor guarantee a reduction in the number of applications next year.
- Essential to the success of this approach is that the first postemergence glyphosate application be made when the majority of the weeds are 4 to 8 inches tall (giant ragweed can be slightly larger). This may occur earlier in the season with this approach compared to when residual herbicides are used in the spring, resulting in the risk of late-emerging weeds that escape treatment. A second postemergence glyphosate application several weeks after the first can therefore often be the key to getting “season-long” control with this approach.
- Because residual herbicides do not last as long into the growing crop when applied in the fall, this approach may not be the most effective for the following types of weeds: those capable of germinating well into the growing season (giant ragweed, marestail, eastern black nightshade, pokeweed, burcucumber); and those that are especially problematic in Roundup Ready soybeans because they demonstrate occasional tolerance to glyphosate or have a history of developing glyphosate resistance (giant ragweed, velvetleaf, lambsquarters, waterhemp, marestail). It is our opinion that this approach also results in more selection pressure for herbicide resistant weeds compared to the following one, since two postemergence glyphosate applications may frequently be required to make this approach work.
- Producers often go with this approach with the hope that it is a two-application program (fall plus postemergence). In fact, many find that this becomes a three-application program (fall plus two postemergence) more often than they would like due to the diversity of weed species that we have in many Ohio soybean fields. Should you find yourself making three applications more often than not, than the next approach may have a better fit.

Approach 2. This approach is effective in Roundup Ready soybeans, and it is the most effective weed management program in fields that will be treated with herbicides this fall and planted to conventional (non-Roundup Ready) soybeans next spring. This is a three-application system consisting of a fall, spring preplant, and postemergence application. Some key points on this approach:
- The primary advantage of this approach compared to the first one is that residual herbicide(s) applied in the spring provide a longer period of weed control after soybean planting compared to fall applications. Because of this, there tends to be a greater number of herbicides from which to choose, since some of the herbicides that are not as long-lived as chlorimuron can still have a good fit in the spring.
- In OSU research, this is the most consistently effective approach to some of the weeds listed above, as well as ALS-resistant weed species. Several residual herbicides can provide season-long control of lambsquarters, velvetleaf, and eastern black nightshade when applied in the spring. There is no question that residual herbicides are most effective on marestail and giant ragweed when applied in the spring (assuming some rain occurs within a week or so of application).
- In our opinion, this approach helps reduce the selection for herbicide-resistant weeds, since it allows for the use of several different herbicide sites of action within the soybean crop.
- This approach tends to provide the most flexibility in the postemergence application timing, which can counteract other factors that wreak havoc with postemergence timing, such as bad weather, a heavy postemergence workload, and slow soybean canopy development.
- A possible disadvantage of this approach – it may be too wet to apply preplant residual herbicides in the spring, although if the field is dry enough to plant it should be dry enough to receive an herbicide application. Another disadvantage for spring applications may be a lack of sufficient rain for activity, which is more of a problem with late-spring applications.
- The preplant residual herbicide can be applied with a low rate of glyphosate or 2,4-D ester to control any small weeds that emerge in the early spring. This is most likely to occur where the fall application lacks residual activity (glyphosate + 2,4-D, for example). It is possible with this approach to apply residual herbicides in fall and spring, which may ultimately be the most effective herbicide program. However, use of residual herbicides is not essential in the fall with this approach. We have heard from a number of producers who have decided to apply glyphosate and 2,4-D in the fall, saving the residual for the spring. Where chlorimuron-based herbicides are used in fall and spring, be cautious about exceeding the maximum amount of chlorimuron for soils with pH of 6.8 or higher.
- a final note on this approach (a disclaimer really): due to variation in weed emergence patterns, soybean development, and the occurrence of herbicide resistance, etc, from year to year, there is no guarantee that a second postemergence application won’t be needed in this approach. However, the chances are much less than with the first approach, and this approach does a better job of managing postemergence workload and controlling the most problematic weeds.

Note on fall treatments and weed control in corn: The use of herbicides in the fall does not really influence the choice of herbicide program used in next year’s corn crop. This is because: a) the fall-applied herbicides (glyphosate, simazine, or Basis) often lack significant residual in the spring on common broadleaf and grass weeds, and b) corn is more sensitive than soybeans to early-season weed competition, resulting in a need for preemergence herbicides to ensure effective corn stand establishment and early-season growth and development.

The Importance of Preemergence Glyphosate Application in No-Till Wheat

Authors: Mark Loux

Many winter weed problems in no-tillage wheat can be managed with a preplant/preemergence application of glyphosate. Dandelion and winter annual weeds such as chickweed and purple deadnettle have been serious problems in wheat in recent years. Producers are often not aware that these weeds are a problem until late fall or early spring. However, many winter annual weeds have emerged by early October and are easily controlled with relatively low rates of glyphosate prior to wheat planting. This can be a more effective treatment for dandelion and winter annuals, compared to the herbicides that can be applied broadcast to wheat in late fall or early spring. Preplant glyphosate application is also by far the most effective and least expensive tool to control winter annual grasses such as annual bluegrass, downy brome and cheat. A dense population of winter annuals or dandelion may have already suppressed wheat growth by the time a fall or spring treatment can be applied.

Dandelion is especially problematic because most postemergence wheat herbicides have limited effectiveness on this weed. Dandelion should be controlled with tillage or glyphosate prior to wheat emergence, since options after emergence are less effective. Tillage must be thorough enough to completely disrupt dandelion plants, and this may not be accomplished with one pass of an implement designed primarily for seedbed preparation. Therefore, consider a glyphosate application prior to tillage for most effective dandelion control. We suggest a glyphosate rate of at least 0.75 lb of glyphosate acid per acre in any field that contains dandelion. Include ammonium sulfate in glyphosate treatments, and the appropriate amount of surfactant if specified by the product label. The activity of herbicides on dandelions may be reduced where fall dandelion growth has been less than vigorous as a result of dry conditions. Also, the preplant herbicide application timing for wheat is somewhat earlier than the optimum timing for fall dandelion control. However, we believe the control attained by a glyphosate application makes it worth the effort even if dandelions are not in the optimum condition. It is possible that increasing the glyphosate rate to 1.1 or 1.5 lbs of glyphosate acid per acre may improve dandelion control prior to wheat planting, but we have not conducted research to verify whether this is the case.

We continue to receive questions about the safety and legality of 2,4-D applied prior to wheat planting. As far as we know, no 2,4-D product label supports the use of 2,4-D. There is some risk of stand reduction and injury to wheat from preplant applications of 2,4-D. We question why producers would want to use 2,4-D, when glyphosate can be applied for about the same cost and provides a similar level of weed control (better on some species). One argument in favor of the use of 2,4-D would be to avoid overuse of glyphosate and slow the development of herbicide resistance. However, 2,4-D can be used with glyphosate in fall and spring herbicide treatments prior to corn and soybean planting, and would probably be best avoided prior to wheat planting.

Producers who have applied glyphosate at the time of no-till wheat planting report that their fields have been relatively free of winter annuals in the spring. However, producers also indicate that they often do not have time to make the application, given the time required to harvest corn and soybeans and plant wheat. Consider having the glyphosate custom applied where time is a limiting factor, especially in fields where winter weeds are evident. Where possible, apply the glyphosate several days before tillage or planting. Otherwise, be sure to apply before the wheat emerges!

Fall Soil Sampling for Next Year's Crop

Authors: Robert Mullen

As soybean harvest progresses, soil sampling probes should be getting shined up and readied for field activity. Soil sampling to determine soil nutrient status is one of the most economical management practices for crop production. Fall sampling should be done to determine the phosphorus, potassium, and soil pH status of soil. These values will be used to determine how much phosphorus (P), potassium (K), and lime should be applied this fall to prepare for next year’s crop. This is especially important as fertilizer prices have increased. If soil analysis reveals the soil contains more P and K than the subsequent crops need, money that was ear-marked for those fertilizer materials can be used elsewhere.

Soil analysis is only as good as the sample that was collected. Utilizing proper techniques to collect soil samples are extremely important and can have dramatic impact on the recommendation. Collect 15 to 20 random 8 inch soil samples from a representative area to create a composite sample. Do not collect less than 15 samples for each area being sampled. This will ensure the sample truly represents the area of interest. Analytical labs in and around Ohio can be found at the following website:

After receiving the analysis from the lab, go the Tri-State Fertilizer Recommendations online to determine the rate needed to maximize production ( Recommended rates of fertilization can also be found at: (this website is based on Tri-State Fertilizer Recommendations). If soil analysis reveals the soil is well above the established critical level, consider not applying that nutrient this fall. If below the critical level, the nutrient should be applied to ensure it is not yield limiting.

Soil sampling should be done at least every three years (if not on a shorter interval) to evaluate trends in soil nutrient status. Sampling the fall prior to spring corn planting is an excellent time to collect soil cores.

Fall and Winter Cover Crops – Can Nitrogen Be “Trapped” for Next Year’s Crop?

Authors: Robert Mullen

Nitrogen prices have increased significantly over the last five years, and unfortunately it appears as if they will continue to increase at least slightly this coming year. The increased cost for this input has led many to find alternative ways to keep more nitrogen around including the use of fall cover crops to “trap” or “catch” nitrogen for subsequent crops. So does this practice work? Can spring corn N rates be decreased if utilizing fall cover crops in continuous corn production systems?

Research suggests that fall cover crops can help mitigate nitrogen loss from agricultural fields (specifically rye). Research conducted in Minnesota revealed a decrease in nitrate loss, measured at the tile discharge, of 13% when rye was planted as a cover crop after corn and prior to soybean. But this decrease in nitrogen loss in the fall does not necessarily translate into subsequent nitrogen release for next year’s crop.

Over 8 site-years in Washington State, use of a non-leguminous cover crop (rye or ryegrass) did not decrease the need for N fertilization with the exception of one year. Thus subsequent fertilizer rates could not be decreased for the next corn crop. Use of vetch as a cover crop did slightly decrease the amount of N needed to optimize yield. In this study all cover crops were planted in late September/early October and allowed to grow all spring until Late April. Data collected in Wisconsin show that in 2 out of 3 years the N rate for optimum production was decreased (approximately 18 lb per acre) if a cover crop (rye, oat, ore triticale) was grown on a sandy soil. The response observed in this study was attributed to a rotational effect rather N release the subsequent spring. This was hypothesized because the decrease in N fertilizer was observed with or without the above-ground biomass being present in the spring.

So why is there not a consistent decrease in the optimum N rate if N that is susceptible to fall/winter loss is captured? It all comes down to timing. Even though N is taken up by a growing plant in the fall does not necessarily mean that it will be released at the optimum time the next spring so that it is not susceptible to loss. If spring planting is delayed and soil conditions are warm enough for mineralization, early spring rains may move the N below the rooting zone down to the tile prior to crop emergence. Another reason is poor growth of the cover crop in the fall and winter. If the cover crop does not accumulate much biomass and subsequent N, intuitively there will be little N benefit for the next crop. Under certain conditions this practice may provide some benefit, but enough is not known to accurately quantify the benefit.

End of Season Cornstalk Nitrate-N Test

Authors: Robert Mullen

The cost of fertilizer nitrogen (N) has sky rocketed this year. Because of the dramatic increase in fertilizer and fuel costs, the end of this growing season is a good time to really examine your fertilizer nitrogen program for corn. Has your application of N routinely been over 200 lbs/a for the last several years? This may or may not have always been the best amount to apply. An “End of Season Cornstalk Nitrate-N Test” can provide some important information about your nitrogen application program.

What Is It and Why Is It Useful?
The cornstalk nitrate-N test determines the concentration of nitrate-N in the lower portion of the cornstalk near the end of the plant’s growth. Knowledge of the nitrate-N concentration in this part of the corn plant will provide information as to whether or not there was insufficient, adequate, or excessive amounts of nitrogen applied early on in the growing season. Corn plants that have inadequate N levels remove N from the lower part of the cornstalk and leaves during the grain-filling period. Research by A. M. Blackmer and A. P. Mallarino of Iowa State University has shown that corn plants that have more N than is needed to attain their maximum yield accumulate nitrate-N in the lower part of the cornstalk. This information can be used to determine if more N than was needed was present in the soil for the corn crop. The test can help reduce application of more N than is really needed year after year.

Dry weather can affect the results so know your soil moisture conditions during the corn growing period. It should be kept in mind that plants under severe droughty conditions may have greater nitrate-N concentrations than plants under normal growing conditions. Records of the test results and soil moisture observations should be kept and evaluated over several years in accordance with fertilizer management programs. Producers who are growing corn on manure amended soils should use the test. In addition, producers who are growing corn after alfalfa should use it as well. A very important use of the test is to make comparisons for different nitrogen management practices.

When and How To Take The Sample:
The sample should be taken 3 weeks after black layers have formed on about 80% of the kernels of most ears. The black layer is a thin black line at the tip of the corn kernel. The black layer coincides with physiological maturity. An 8-inch portion of the stalk 6-14 inches above the soil should be sampled. Remove leaf sheaths from the stalk. Fifteen 8-inch segments should be collected to from the sample to be submitted to the laboratory. Areas that differ in management or sample soil type should be sampled separately. The sample should be representative of corn growing in the area of interest. Place samples in paper bags (not plastic) and send them to the laboratory as soon as possible after collection.

Where To Send Samples:
Most soil testing laboratories also do the “End of Season Cornstalk Nitrate-N Test”. Be sure to contact the laboratory before collecting the samples as they may have special forms and bags for this type of test. Your local County Extension Educator can assist you in locating an appropriate laboratory.

Interpretive Guidelines for the Nitrate-N Concentrations:

< 250 ppm --- Low: Indicates a high probability that greater availability of N would have given a higher yield. Visual symptoms usually present.

250 – 700 ppm --- Marginal: Indicates that N availability was close to the amount needed by the crop.

702 – 2,000 ppm --- Optimal: Indicates a high probability that N availability was within the range needed for optimum yield.

> 2,000 ppm --- Excess: Indicates a high probability that N availability was greater than needed for optimum yield.

If the test shows > 2,000 ppm year after year, you may want to reduce the amount of N applied for the next year’s crop. Dry weather can affect the results. Under conditions of severe drought, the plants may have greater amount of nitrate-N than plants under normal growing conditions. Be sure to take soil moisture into account when making the interpretation.

Archive Issue Contributors: 

Anne Dorrance, Dennis Mills and Pierce Paul (Plant Pathology), Ron Hammond and Bruce Eisley (Entomology), Mark Loux, Jeff Stachler, and Tony Dobbels (Weed Science), Robert Mullen and Maurice Watson (Soil Fertility), and Peter Thomison (Corn Production). Extension Educators: Steve Foster (Darke), Howard Seigrist (Licking), Roger Bender (Shelby), Harold Watters (Champaign), Ed Lentz (Seneca), Mark Koenig (Sandusky), Dusty Sonnenberg (Henry), Curtis Young (Allen), Steve Bartels (Butler), Steve Prochaska (Crawford), Greg La Barge (Fulton), and Andy Kleinschmidt (Van Wert).

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.