CFAES Give Today
Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2007-04

Dates Covered: 
February 20, 2007 - March 6, 2007
Harold Watters

Is It OK to Apply Nitrogen to Wheat Before Greenup?

Authors: Robert Mullen, Edwin Lentz

Many of us would like to apply N to wheat now while the ground is still frozen (at least the surface) rather than waiting for proper soil conditions in March. Though we may save time and labor with a February application, we run the risk of losing most of the N (a costly error with existing high N prices).

Ohio State University research completed in 2003 revealed that loss of N from a single N application prior to spring green-up may have yield reductions of 19% compared to applications between initial greenup and early stem elongation. This loss occurred for all N sources used in the study (ammonium sulfate, urea and 28%). In this same study, yields did not decrease as long as spring application was made between greenup and early stem elongation.

Corn Yield Response to Tillage and Rotation on Poorly Drained Soils

Authors: Warren Dick, Randall Reeder, Alan Sundermeier, Peter Thomison, Robert Mullen

Studies in Ohio and other Corn Belt states have shown that increasing the amount of tillage from no-tillage to chisel to moldboard plow decreases the yield difference between continuous corn and corn rotated with soybean on poorly drained soils. No-till cropping systems are more likely to succeed on poorly drained soils if corn follows soybean rather than corn. On well-drained soils, crop rotation with soybeans had less effect on corn response to tillage.

The influence of crop rotation on corn response to tillage and soil type has been well documented in long-term OSU-OARDC studies conducted on poorly drained Hoytville silty clay soils in NW Ohio. This research has consistently shown that yield differences between no-till and tilled ground were greatly reduced where corn followed soybean.

Dr. Warren Dick and Dr. Randall Reeder have maintained two long-term rotation experiments at the OSU -OARDC Northwest Agricultural Research Station in Wood County. Dr. Dick’s plots have been planted in continuous corn or a corn soybean rotation for 44 years while Dr. Reeder’s plots have been cropped in different cropping sequences for 23 years. The primary objective of this research has been to study cropping sequences and tillage effects on crop production on tile drained Hoytville silty clay soil. Much of Northwest Ohio’s corn is produced on this soil or soils with similar characteristics.

For these multi-year crop rotation studies, yields for corn after soybean, averaged across tillage, were 10 to 13% greater than yields after corn. However, the magnitude of the rotation effect was strongly influenced by tillage. In no-till systems, corn following soybean yielded 19 to 22% more than corn following corn. When tillage was used, the yield advantage was far less pro¬nounced with yields for corn after soybean averaging 1% less to 7% more than those after corn.

Purdue University agronomists have also maintained long-term rotation tillage trials near West Lafayette, Indiana. In studies conducted since 1975 on a dark prairie silty clay loam soil, the average yield “drag” for continuous corn versus corn following soybean during the past ten years (1997-2006) was 3, 5, and 18% percent for moldboard plow, chisel plow, and no-till systems respectively.

For additional information on the NW Ohio rotation-tillage studies described above and recently established research comparing more diverse cropping sequences and tillage, consult Extension Fact sheet AGF506 “Managing Tillage and Crop Rotations in Northwest Ohio” available soon.

Assessing Soil Nitrogen Availability

Authors: Robert Mullen, Edwin Lentz

The presidedress soil nitrate test (PSNT) or late spring nitrate test (LSNT) is often promoted as a soil testing tool that can be used to aid in nitrogen management decisions. Soil samples are generally collected between mid-May to mid-June whenever sidedress applications of nitrogen are being made. The question is when should I use the PSNT and what does the PSNT tell me as a crop manager?

The goal is to provide better nitrogen recommendations for crop producers. Nitrogen transformations that occur in the soil are dynamic and strongly influenced by environmental conditions because they are the result of soil biological activity. The transformation we are primarily concerned with in agriculture is the mineralization of organic nitrogen to inorganic forms (initially ammonium and eventually nitrate). If mineralization rates for soils could be predicted for a given growing season nitrogen recommendation strategies could be improved. Because accurate models do not exist to quantify this phenomenon we must rely on a snapshot in time of what has occurred in the soil (i.e. the PSNT/LSNT) or some other alternative method (reference/nitrogen rich strips). The PSNT/LSNT conducted on soils that do not have a manure history or previous forage legume crop rarely return levels high enough to prompt a decision. The PSNT/LSNT is almost exclusively promoted for fields that have received recent manure applications or where corn is following a forage legume crop.

Depending upon the PSNT/LSNT level we get an estimate of the likelihood of seeing a response to additional nitrogen fertilizer, but we do not get an actual nitrogen recommendation. PSNT/LSNT values near 25-30 ppm are unlikely to benefit from additional nitrogen fertilizer, and the higher the value the less likely the need for supplemental nitrogen. The problem arises when PSNT/LSNT values are less than 25 ppm. PSNT/LSNT values below this level may or may not respond to additional nitrogen fertilizer, but the stock recommendation would be that they do require more nitrogen. There can be sites that have a low PSNT/LSNT value but show no response to nitrogen fertilization. This is a major limitation of the PSNT/LSNT.

The Illinois Soil Nitrogen Test

The Holy Grail for soil fertility has long been the search for a method of determining nitrogen (N) mineralization (release of organic N to a plant available form) to make better N recommendations for cereal crop production. Researchers have spent careers attempting to understand and model this phenomenon. Estimating N mineralization and subsequent N responsiveness is the purpose of the Illinois Soil Nitrogen Test (ISNT) (Mulvaney et al., 2001). The ISNT is designed to quantify a particular fraction of soil organic matter that is easily mineralized – the amino sugar N fraction. This fraction of soil organic matter represents the form that has the potential to be mineralized and made plant available. Higher concentrations of amino-sugar N should mean less likelihood of N response, and initial data analysis revealed this to be true. Soils that contained less than 225 ppm amino-sugar N in Illinois were determined to be responsive to N fertilization, and soils with greater than 235 ppm amino-sugar N were considered non-responsive. The ISNT was not however calibrated to a specific N rate (i.e. an amino-sugar N value of 150 ppm could not be used to identify a specific N recommendation). It was developed to separate responsive sites from non-responsive sites. While work in Illinois showed the ISNT had promise, research conducted in other states is not as conclusive.

Iowa has evaluated the ISNT for use on their soils and could not identify a critical value for amino-sugar N that would differentiate responsive sites from non-responsive sites (Sawyer et al., 2003). The majority of soils evaluated in the Iowa study tested between 200 and 500 ppm amino-sugar N, but sites classified as non-responsive by the critical values established initially did respond to fertilizer N with as much as a 50% increase in yield. Wisconsin has also evaluated the ISNT for use in their production environment and found that they could not identify a critical value ( The initial critical values (established in Illinois) were not appropriate for Iowa or Wisconsin soils and growing conditions. In fact, Iowa and Wisconsin could not establish correlations between the ISNT and crop responsiveness. It is unreasonable for Ohio producers to assume the critical values that have been established in Illinois would be appropriate for Ohio.

Fundamentally, the ISNT has a major hurdle to overcome. While the amino-sugar N fraction of soil organic matter may represent the most easily mineralized portion (potential mineralization), mineralization is not just controlled by the amount of easily mineralized N in the soil. It is also controlled by weather and the soil environment. As I make reference to in most of my discussions on N management, long-term weather predictions are not accurate enough to model N mineralization. Thus predictions of mineralization are not accurate enough to affect N recommendations (at least not yet). Another hurdle is that any fertilizer material recently applied that contributes significant ammonical N (ammonia/ammonium forms of N) such as animal waste or anhydrous ammonia can inflate the amino-sugar N value. This can be accounted for however by measuring the ammonium concentration of N in the soil (additional soil test information). Ohio State University does not recommend this test as means to adjust fertilizer nitrogen application rate decisions.

Continuous Corn – Be Ready to Pay for More Nitrogen

Authors: Robert Mullen, Edwin Lentz

Higher corn prices may be enough to convince some producers to increase their corn after corn acres, but be aware that your nitrogen fertility bill has to go up compared to corn after soybeans. One of the primary benefits of growing corn after soybean is the decreased demand for supplemental nitrogen fertilizer. The difference in corn nitrogen demand following another grass crop (compared to a legume) has been known for some time and is usually reflected in nitrogen recommendations. The “credit” for a prior soybean crop ranges between 30 and 40 pounds of nitrogen per acre. The reason for the decreased need for supplemental nitrogen fertilizer is not fully understood, but research suggests that it is due to the nature and amount of crop residue returned to the soil. Far less residue is returned to the soil following a soybean crop and the nature of the residue is much different. The carbon:nitrogen (C:N) ratio of soybean residue generally ranges between 30-40:1 while corn residue generally ranges between 80-90:1. The increased C:N ratio and total amount of residue returned from the corn crop causes a slow and sizable immobilization of soil nitrogen to satisfy microbial demand so that the residue can be broken down. Soybean residue too requires immobilization, but the immobilization proceeds more rapidly and nitrogen demand by microbes is not as great. Once the residue has been broken down, the new equilibrium that is reached results in net mineralization of organic nitrogen (from the recently added residue) decreasing the need for supplemental nitrogen fertilizer.

Data collected in Ohio from 47 corn after soybean sites and 21 corn after corn/wheat sites show the average difference in the agronomic optimum nitrogen rate of 31 pounds per acre. Bottomline – corn after corn requires more supplemental fertilizer than corn after soybeans. Economic nitrogen recommendations, available online, take into account these differences between corn after corn and corn after soybeans, so the credit is actually built into the recommendation (the credit does not have to subtracted – it is already done) (recommendations available at Be prepared to pay for more nitrogen if you choose to grow more corn after corn.

Continuous Corn: Its Effect on Diseases

Authors: Pierce Paul

In recent years, Ohio corn growers have not had to deal with major disease problems. With the exception of a few localized stalk rot, ear mold, and leaf blight problems, growers have suffered very little yield and quality losses due to diseases. This is largely because most growers practice crop rotation and plant hybrids that are resistant to major diseases. However, this situation will likely change completely over the next few years if Ohio’s growers switch to continuous corn. Most of our main corn disease problems are associated with conservation tillage and continuous corn cropping practices. Major, potentially yield-limiting foliar diseases such as gray leaf spot, northern corn leaf blight, anthracnose leaf blight, and eye spot are generally more problematic in continuous corn production systems. In addition, stalk and ear rots are very common in this type of cropping system.

Economically important foliar, ear, and stalk diseases such as gray leaf spot (Cercospore zeae-maydis), northern corn leaf blight (Exserohilum turcicum), eyespot (Kabatiella zeae), anthracnose leaf blight and stalk rot (Colletotrichum graminicola), Gibberella ear and stalk rots (Gibberella zeae), and Diplodia ear and stalk rots (Stenocarpella maydis) are caused by pathogens that survive the winter in crop residue left on the soil surface. Once conditions become favorable (warm and humid) in the spring, these fungi grow and produce spores that are wind-blown or splashed onto the leaves, stalks and ears of the new crop, causing new infections. Although each disease may occur separately and develops best under a separate set of weather conditions, damage caused by one disease may increase problems associated with another. For instance, extensive blighting of the upper leaves due to gray leaf spot and northern corn leaf blight may lead to stalk and ear rot problems. Leaves in the middle and upper parts of the plant produce most of the sugars (about 75%) needed for grain production, so, a reduction in healthy leaf area means that less sugar, and as a result, less grain will be produced. To compensate for low sugar production by the leaves, sugars are removed from the stalk, leading to poor stalk quality, stalk rots, and lodging. Compound losses (direct and indirect) due to gray leaf spot, for example, may be as high as 90% in susceptible hybrids under favorable weather conditions.

Crop rotation and tillage are two of the most effective management strategies for reducing losses due to all of the diseases mentioned above. Both practices lead to destruction of crop residue, reducing survival of pathogens from one year to another. Planting a non host crop such as soybeans breaks the cycle of most corn pathogens, since they depend largely on corn or some other related host to complete their live cycle. However, in a continuous corn cropping system, especially when reduced tillage or no tillage is practiced, pathogens are carried over from one growing season to another, eventually building up to levels likely to cause grain yield and quality losses. Although planting a resistant hybrid or using a fungicide may reduce losses due to diseases in a conservation tillage-continuous corn cropping system, no hybrid is equally resistant to and no fungicide is equally effective against all the diseases likely to develop in such a system.

Growers willing to plant corn after corn will have to be prepared to use multiple management strategies to minimize disease problems.
1. Use some form of tillage to bury crop residue. Without crop rotation, tillage becomes absolutely necessary to reduce pathogen buildup from one season to another.
2. Plant hybrids with good disease resistant and tolerance. Some hybrids are more tolerant than others, meaning that for a given level of disease, the more tolerant hybrids will suffer less yield reduction than the less tolerant hybrids.
3. Use fungicides to control foliar diseases when susceptible hybrids are planted and weather conditions are favorable.
4. Select hybrids with good standability and stalk strength.
5. Use adequate fertility programs based on soil tests and avoid excessive rates of nitrogen or other nutrients.
6. Control insect pests and weeds. Aphids and leafhoppers may transmit viruses to corn from weeds. In addition, root worms and stalk borer may cause injuries to plant roots and stalks, permitting stalk rot fungi to enter the plant.

Weed Management Issues in Continuous Corn

Authors: Mark Loux

The continuous planting of summer annual crops in Ohio tends to make weed control more difficult, since it promotes the continuous selection for weed species that are most successful in this cropping system. Within this summer annual cropping system, planting a monoculture of corn or soybeans can result in greater weed problems over the long term, due to the propensity for overuse of certain herbicides (atrazine in continuous corn, for example, or glyphosate in continuous Roundup Ready soybeans). Rotation of crops has historically resulted in greater diversity in herbicide use. As a result, a weed that was not well controlled by herbicides in one crop might be effectively controlled with different herbicides in the next year’s crop. This is changing due to the increase in Roundup Ready corn and therefore continuous Roundup Ready acres, which will most likely result in over-reliance on glyphosate and correspondingly less herbicide diversity.

We are not convinced that the planting of continuous corn really poses more serious issues for weed management, compared with a rotation of corn and soybeans, as long as appropriate weed management strategies are used. We have many effective herbicides for use in corn. The question is – will we integrate them to most effectively manage the really tough weeds and minimize selection for herbicide resistance? Some considerations for weed management in continuous corn follow, with special emphasis on Roundup Ready corn.

- Use tillage or preplant burndown herbicides to ensure that corn is planted into a weed-free seedbed. Planting soybeans into weedy fields, and delaying the first glyphosate application until sometime after soybeans emerge contributed to the development of glyphosate resistance in giant ragweed and marestail, and also the general increase in winter annual weeds and dandelions.

- Select a herbicide program that is appropriate for the weeds in the field. A total preemergence herbicide program can control many annual weeds, but frequently fails to provide season-long control of weeds that can emerge in mid-season, such as dense annual grass infestations, giant ragweed, burcucumber, and perennial weeds. A combination of preemergence and postemergence herbicide applications is more effective for these type of weeds, and in any field with a history of poor weed control.

- Use a diversity of herbicide sites of action within and over years, to reduce the risk of herbicide resistance. This will be more easily accomplished where a combination of preemergence and postemergence herbicides are used, compared with a total preemergence or total postemergence approach. Triazine resistance developed in continuous corn in the 1970’s due to over-reliance on atrazine. Avoid using atrazine as the sole broadleaf herbicide in continuous corn, and avoid continuous use of ALS inhibitors for control of the same weeds every year.

- We assume that glyphosate will be a primary component of herbicide programs in continuous Roundup Ready corn, but other herbicides should be used along with glyphosate to reduce the selection for glyphosate resistance. Examples: 1) Apply preemergence herbicides at the time of planting to reduce the weed population that will need to be controlled with postemergence glyphosate applications; 2) In a tilled field where a total postemergence program is planned, mix glyphosate with other herbicides that can help control emerged weeds and provide residual weed control (which essentially eliminates the need for a second postemergence application); and 3) where glyphosate is applied late postemergence following preemergence herbicides, mix it with low rates of other postemergence herbicides (Status, Callisto, or Resolve, for example).

- Manage postemergence glyphosate applications appropriately. Apply when weeds are small. Increase the glyphosate rate in any sub-optimum weed control situation, such as large weeds, or weeds that are developing a history of control problems (lambsquarters, giant ragweed, morningglory, pokeweed).

- Corn hybrids that have the BT Herculex trait are also Liberty Link (resistant to Liberty). This includes stacked trait hybrids that have a combination of glyphosate resistance and the BT Herculex trait (Pioneer, Dow, and Syngenta hybrids, among others). Consider using Liberty in postemergence applications to these hybrids, instead of glyphosate. There is about a $6 per acre difference in cost between glyphosate and Liberty (with current rebates), but use of Liberty breaks the cycle of continuous glyphosate use, and this can have long-term benefits. Growers with a history of giant ragweed control problems with glyphosate should strongly consider use of Liberty on hybrids that carry the Liberty Link trait.

- Some consideration should be given to the type of corn that is used each year in a continuous corn system for several different reasons. From a herbicide use standpoint, growers have a choice of: conventional hybrids (cannot be treated postemergence with glyphosate or Liberty); glyphosate-resistant hybrids such as Roundup Ready or GT Agrisure (can be treated postemergence with glyphosate but not Liberty); Liberty Link hybrids (can be treated postemergence with Liberty but not glyphosate); stacked-trait hybrids that contain both the glyphosate resistance trait and the Liberty Link trait (can be treated postemergence with glyphosate or Liberty). Rotation of these types of corn from year to year, and corresponding rotation of herbicides, should reduce the risk of resistance to glyphosate and other herbicides. Beyond this, there is the issue of volunteer corn (see next bullet).

- One of the more insightful questions we received from growers at winter meetings this year involved the potential problems controlling volunteer corn in continuous cornfields, since the volunteer corn could be herbicide-resistant. For example, planting continuous Roundup Ready corn would result in the possibility of volunteer Roundup Ready corn in next year’s corn. Postemergence applications of glyphosate would fail to control the volunteer corn, which would then be a weed problem. In a rotation consisting of two years of corn followed by a year of soybeans, this problem could largely be avoided by planting conventional corn the first year, and Roundup Ready corn the second year. This would allow use of glyphosate in the second year of corn to control the volunteer corn. Alternatively, Roundup Ready corn could be planted the first year, and a hybrid containing the Liberty Link trait (BT Herculex or stack of BT Herculex plus Roundup Ready) in the second year. Liberty could then be applied postemergence in the second year of corn, and would control or at least greatly injure the volunteer Roundup Ready corn. Infestations of volunteer corn vary considerably from year to year, based on the stalk lodging and weather during the previous year’s harvest season. We can’t predict how significant the issue of volunteer corn will become in continuous corn, but some thought should be given to the rotation of corn hybrid types to minimize the risk of control problems.

Increasing Your Corn Acres with Corn Following Corn? Do Not Forget About the Insects!

Authors: Ron Hammond, Bruce Eisley

With many growers planning an increase in their corn acreage by planting corn following corn, the possibility of increased pressure across Ohio from western and northern corn rootworms is higher. With the exception of the western corn rootworm variant that lays its eggs in soybean fields, now causing concerns in western Ohio, adult rootworms normally lay their eggs in corn fields in August, with larvae hatching the following year and feeding on corn roots if present. The age-old way to manage this problem has always been, and continues to be in most of Ohio, rotation to another crop. Most growers in Ohio have not had to worry about rootworms because of crop rotation.

However, with many growers planning on corn following corn, the need to protect corn from rootworms this coming summer is greater. Growers should remember that there are numerous tactics they can use to combat this insect. Soil insecticides continue to be excellent choices (see list of currently labeled insecticides at: They are effective and give good, consistent control. Transgenic corn hybrids containing the RW or rootworm gene are excellent choices, whether alone or in stacked hybrids containing the genes for corn borer control or Roundup Ready resistance. When using transgenic hybrids, first base your hybrid selection on hybrids that have superior agronomic traits for your growing area. Also, remember that if transgenic corn hybrids are planted, a 20% refuge area of non-transgenic hybrids is required. Check with your seed supplier for details on the refuge area. The final choices for rootworm management are the higher rates of seed treatments, Cruiser 1250 or Poncho 1250. Although data from Ohio and other Midwestern states have shown that these seed treatments do NOT manage rootworms well under high rootworm feeding pressure, they do give adequate control if rootworm populations are low to moderate. Thus, they should give good rootworm control in many fields in Ohio. We would suggest that you consider using seed treatments in those areas where rootworms have not been a problem in the past.

Although rootworms are the main insect of concern with corn following corn, we always get asked about the potential for other insect pests that might increase. Actually, other corn pests should not become either greater or lesser problems. Insects such as black cutworms and armyworms migrate from southern states, and thus, whether corn follows corn or soybeans is immaterial. The primary concern with these two insects is whether fields are weedy or have a grass cover crop, which attract these insects. Most other insects, although overwintering in nearby areas, also come into the field each spring from outside the field. This situation also pertains to European corn borer. Although they overwinter in corn fields, adult moths move in and out of corn on a daily basis, so having been in corn the previous year will not be great concern. Although slugs will continue to remain in a field, they can cause problems in whatever crop is grown the coming year, whether corn or soybean.

Thus, except for the western and northern corn rootworms, corn following corn should not increase or decrease the level of insect pests. However, rootworms are the one insect pest that probably need controlling when corn follows corn. For other problems, we continue to recommend scouting and treating when necessary.

Increasing Your Corn Acres? Use This Opportunity to Manage Soybean Cyst Nematode

Authors: Dennis Mills, Nancy Taylor, Anne Dorrance

Soybean growers in Ohio may be unknowingly losing profits from their soybean crop due to the presence of soybean cyst nematode. Soybean cyst nematode is a plant parasite that is best managed with crop rotation. Rotating to non-host crops (corn, small grains and alfalfa) may be the most effective method of controlling soybean cyst nematode. Average soybean yield losses attributed to SCN in Ohio are estimated to be 15%, but yield damage can range from slight to near-total losses depending on various factors including severity of infestation, soil type, soybean variety, weather conditions, and other stress-inducing factors (e.g., presence of weeds or other pathogens). Symptoms of SCN infection in soybeans may not be evident under low infestations or when good soybean growing conditions exist, however, yield reductions may still occur from relatively low levels of infestation. SCN populations typically decline by 50% per year under non-host crops in Ohio. In fields where soybean cyst nematodes are high, grow at least three years of non-host crops between soybean crops. It should be noted that the nematode will not be eliminated in these fields. Therefore, if soybeans are repeatedly planted for several years, SCN will again become yield limiting. SCN populations can increase 10 to 30 fold per year on susceptible soybeans. Soybeans double cropped with wheat are usually not severely damaged but do allow SCN to increase in the field.

To ensure that this strategy works – the fields must be free of host plants. Unfortunately, SCN can reproduce on some winter annual weeds, especially purple deadnettle, therefore these weeds must be managed as well: see The number of SCN cysts formed on purple deadnettle is almost equal to that produced on a highly-susceptible soybean variety. The numbers of cysts formed on the roots of other weed hosts are lower overall, however, significant levels of SCN reproduction are observed on henbit and field pennycress.

Of course the best management program for SCN is to soil sample fields to get a reading of the level in individual fields through the C. Wayne Ellett Plant and Pest Diagnostic Clinic,, then plan accordingly using crop rotation and resistant varieties if necessary. Fields can be sampled anytime of the year but following harvest is the optimum time to sample.

To keep soybean fields profitable for the long term, take advantage of high corn prices while managing soybean cyst nematode and keeping tabs on what these populations are doing. Now is the opportune time to use a planned rotation in those SCN problem fields as a very effective, economical management tool.

2007 New Herbicide Update

Authors: Mark Loux

This article summarizes new herbicide information for the past year or so. Most of the herbicides mentioned here are also listed in the “2007 Weed Control Guide for Ohio and Indiana”, but several have been labeled since last fall, when the Guide was published.

Impact (AMVAC) can be applied postemergence to corn for control of primarily broadleaf weeds. The active ingredient is topramezone, which is an HPPD inhibitor, the same site of action as Callisto. Spectrum of broadleaf weed control is also similar to Callisto. Impact is most effective when applied in combination with atrazine, and can be weak on ragweeds in the absence of atrazine. Impact also has activity on small annual grass weeds, and while it should not be relied upon to provide complete control of grasses, it could help control grasses that escape preemergence herbicides. Impact can be applied to field corn, seed corn, popcorn, and sweet corn, but users should check with seed supplier for hybrid and inbred tolerance information before use.

Resolve (DuPont) is labeled for preemergence and postemergence application in corn. The active ingredient, rimsulfuron, can provide several weeks of control of annual grasses, lambsquarters, pigweeds, smartweed, and velvetleaf. This product is geared primarily for use in a Roundup Ready corn program, or other preemergence plus postemergence programs. Resolve can be applied preemergence (with atrazine to improve control of a number of weeds), and followed with a postemergence application of glyphosate in Roundup Ready corn. In comparison to preemergence application of atrazine alone, the combination of atrazine plus Resolve will improve control of annual grasses, and triazine-resistant lambsquarters and pigweed. Resolve can also be applied postemergence in combination with glyphosate, to provide several weeks of residual control after the postemergence application.

Status (BASF) is a premix of diflufenzopyr plus dicamba (Distinct) plus a safener, isoxadifen, for postemergence use in corn. The safener reduces the risk of corn injury, including the brittle corn stalks that can occur from application of dicamba to corn that is more than about 10 inches tall. Status can be applied broadcast to corn that is 4 to 36 inches tall (V2 to V10), and can be applied with surfactant, crop oil concentrate, or methylated seed oil.

SureStart (Dow) is a premix of acetochlor (Surpass) plus Hornet for preemergence or postemergence use in Roundup Ready and Liberty Link corn. This product provides residual control of many grass and broadleaf weeds. Registration of this product is expected in 2007.

Canopy DF (DuPont), the original Canopy, is back. Canopy is a premix of chlorimuron and metribuzin for preplant or preemergence use in soybeans. The spectrum of broadleaf weed control is similar overall to that of Synchrony XP and Canopy EX. The metribuzin in Canopy can improve control of ALS-resistant waterhemp, common ragweed, and pigweed. However, the rates of Canopy used most often, 2.2 to 4 oz, provide the equivalent of only about 1.8 to 3.4 oz of Sencor 75DF, and control of these weeds will be improved with the addition of another 4 to 6 oz of metribuzin. Canopy can be applied in the fall prior to soybean planting, and it spectrum of winter weed control is overall similar to Canopy EX when applied with 2,4-D ester. The one exception is common chickweed, which may not be adequately controlled by Canopy when present in dense infestations. Control of this weed can be obtained with fall Canopy treatments by adding glyphosate, metribuzin, or Express.

Valor XLT (Valent) is a premix of Valor plus chlorimuron (Classic) for preplant or preemergence use in soybeans. This product is most similar to Gangster in weed control spectrum. A 3 oz rate of Valor XLT contains 1.75 oz of Valor and the same amount of chlorimuron as 3 oz of CanopyDF. The soil pH restrictions on the use of Valor XLT are also similar to Canopy. Valor XLT rates of 3 to 5 oz should only be used where the composite soil pH is less than 7.0.

Sonic/Authority First (Dow/FMC) is a premix of sulfentrazone (Authority/Spartan) and cloransulam (FirstRate) for preplant or preemergence use in soybeans. The 3 oz rate of this product contains the equivalent of 2.6 oz of Authority/Spartan and 0.3 oz of FirstRate. Authority First/Sonic is roughly similar to Gangster in weed control spectrum, but is not effective for control/suppression of ALS-resistant common ragweed. Also, the amount of Authority/Spartan in the 3 oz rate of Authority First/Sonic may be too low for most effective residual control of waterhemp, ALS-resistant marestail, and black nightshade.

Prefix (Syngenta) is a co-pack of s-metolachlor (Dual II Magnum) plus fomesafen (Reflex) for preplant or preemergence use in soybeans. Prefix is available as a co-pack for 2007, but should be formulated as a premix product for 2008. This product is geared for use as part of a preemergence plus postemergence program in Roundup Ready soybeans. Prefix can be applied prior to or at planting to provide several weeks of control of annual grasses, pigweeds, black nightshade, and waterhemp, and followed with a postemergence application of glyphosate.

Axial (Syngenta) can be applied to wheat for control of annual ryegrass, foxtails and barnyardgrass. The active ingredient is pinoxaden, an ACCase inhibitor (same site of action as clethodim, Assure II, etc). Wheat should be in the 2-leaf to pre-boot stage at the time of application, and grasses should have 1 to 5 leaves and less than 3 tillers. Winter annual weeds such as annual ryegrass are generally most easily controlled when small in the fall, and more difficult to control in spring after they have over-wintered.

Autumn (Bayer) can be applied in the fall or early spring prior to corn planting for control of winter annual weeds and dandelion. Autumn is most effective for winter weed control when applied in the fall, and when applied in combination with 2,4-D or glyphosate. The active ingredient is iodosulfuron-methyl (one of the components of Equip), an ALS inhibitor. Autumn controls emerged weeds, and does not provide residual control of weeds that emerge the following spring.

Milestone (Dow AgroSciences) contains aminopyralid, a growth regulator herbicide for use in grass pastures, and CRP and non-crop areas. Milestone controls musk, bull, and Canada thistle, and a number of other broadleaf weeds, but has little activity on brushy and woody species. Aminopyralid is also available as a premix with 2,4-D, named Forefront. The addition of 2,4-D broadens the spectrum considerably to control many broadleaf weed species in pastures and non-crop areas.

Reminder - Conservation Tillage Conference and Agronomy Offerings for March

Authors: Harold Watters

1) Conservation Tillage and Technology Conference - February 22 & 23
This annual event will be held this Thursday and Friday, February 22 and 23 in the MacIntosh Center of the Ohio Northern University Campus in Ada, Ohio. Walk-in registration is $40 per day or $60 for the two days. For more information call the Allen SWCD at 419-223-0040 then press 3, the Hancock County Extension office at 419-422-3851 or see the website: The opening session starts at 9:30 AM on Thursday.


2) The Southwest Ohio Corn Growers Winter Meeting March 8

The Southwest Ohio Corn Growers Association will hold their winter meeting on March 8, 2007 at the Presbyterian Church of Wilmington, in Wilmington, Oh. The church is located on Timber Glen Drive, just off of SR 730 in Wilmington, OH.

The featured speaker will be Robert Boggs, the new director of the Ohio Department of Agriculture. Director Boggs will be taking the opportunity to introduce himself to growers in Southern Ohio, and will give insight to how the department’s policy will develop under his leadership. In addition to Director Boggs, Dwayne Seikman of the Ohio Corn Growers Association will provide an update on the organizations work from 2006 and its plans for 2007. Mark Abraham, Cargill Bloomingburg, will provide a market update and speak on the progress of the ASA Alliance ethanol plant under construction in Bloomingburg, OH.

Registration will begin at 6:00 PM and dinner will be served at 6:30 PM. Although the program is free, if you plan to attend this year’s event we ask that you register by calling the Fayette County Extension Office at (740) 335-1150 or e-mail John Yost at

3) Managed Grazing School for Beginners

This event includes classroom and on-farm visits to help beginners manage forages for their livestock grazing operation. There are four sessions starting on March 8th, ending March 31 with the farm visit. Register with OSU Extension Carroll County, 32 West Main Street, Carrollton OH 46615 by February 28th. Cost is $50 per person with family discounts available. Call OSU Extension Carroll County at 330-627-4310 for more information. Sponsors also include USDA, NRCS and the Soil & Water Conservation Districts of Carroll, Harrison, Jefferson and Tuscarawas Counties.

4) Conservation Tillage Club
March 13 from 7:30 a.m. to 10:00 a.m.
County of Meeting Location: Hardin/Logan
Location: Plaza Inn in Mt Victory
CCA Credits: Yes
PAT Credits: No
For more information: see or Gene McClure at or 419-674-2297

Archive Issue Contributors: 

Peter Thomison (Corn Production), Anne Dorrance, Pierce Paul and Dennis Mills (Plant Pathology), Warren Dick and Robert Mullen (Soil Fertility), Ed Lentz (Agronomy), Ron Hammond and Bruce Eisley (Entomology) and Mark Loux (Weed Science), Randall Reeder (Ag Engineering) and Nancy Taylor (Plant Diagnostic Clinic). Extension Agents: Roger Bender (Shelby), Howard Siecrist (Licking), Glen Arnold (Putnam), Keith Diedrick (Wayne), Jonah Johnson (Clark), Alan Sundermeier (Wood) and Harold Watters (Champaign).

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.