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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2004-04

Dates Covered: 
February 18, 2004 - March 3, 2004
Greg La Barge

Seed Treatment Insecticides

Authors: Ron Hammond, Bruce Eisley

There has been the addition of 2 new hopperbox insecticide seed treatments for corn in 2004. They are Concur and Latitude and both contain Gaucho (imidacloprid) as the insecticide. Because there have been several new seed treatments (both hopperbox and seed applied) in the past year, we have put together a table which lists the seed treatment, active ingredient, rate and insects listed on the label. This table is listed in the corn section of the Agronomic Crops Insects web site at:

We studied several of these seed treatments for efficacy against several insects in 2003 and the

When Is A Generic Not A Generic?

Authors: Mark Loux

The generic herbicide market is expanding with many widely used active ingredients being sold under various trade names. The proliferation of generic products is a natural consequence of the expiration of patents, and this trend will continue. The availability of generic products can be beneficial to producers, since it is often accompanied by a reduction in price.

In some cases, generic products are the exact same formulation sold under a different trade name, due to marketing agreements between companies. For example, Dupont sells Cinch ATZ, which is the same formulation as Bicep II Magnum, and Agriliance sells Confidence and Confidence Xtra, which are the same as Harness and Harness Xtra.

In other cases, a company other than the original patent holder manufactures the generic, and the formulation may vary somewhat from the original. This often results in a formulation that is similar to the original with regard to the percentage of active ingredient, however, and the label is often consistent with if not identical to the original.

Metolachlor has now joined the ranks of active ingredients available as generic products. Syngenta sells metolachlor in Dual II Magnum and Bicep II Magnum, and Sipcam sells metolachlor in Stalwart C and Stalwart Xtra. For a good discussion of the differences between metolachlor products and the possible ramifications, we recommend the article on the Iowa State University Weed Science web page.

Weed Management In Conventional (Non-GMO) Soybeans

Authors: Mark Loux

Producers of non-GMO soybeans should strongly consider the use of a two-pass herbicide program – a preplant herbicide treatment that includes burndown plus residual herbicides followed by a broad-spectrum postemergence treatment. Total postemergence (or burndown without residual followed by postemergence) should be used only in fields with low weed populations and no history of ALS resistance. Use of a residual herbicide in the preplant treatment increases the cost of weed management, but will result in more consistent control of annual grasses, lambsquarters, black nightshade, giant ragweed, and ALS-resistant weeds.

Some of the issues for weed control in non-GMO soybeans are:

1. Planting non-GMO soybeans into a weed-free seedbed is essential, since postemergence herbicides will not adequately control typical spring no-till weeds. No-till normal soybeans therefore require an effective preplant burndown treatment, which should usually include glyphosate and 2,4-D.

2. Populations of ALS-resistant weeds, especially common and giant ragweed and marestail, may be present in non-GMO soybean fields. ALS resistance will be more likely if a field has been planted with normal soybeans over the past several years. We recommend planting non-GMO soybeans in rotation with corn and Roundup Ready soybeans (and wheat if possible), which will help minimize weed problems in the year that non-GMO soybeans are planted.

3. Unlike glyphosate, which can control large weeds at high rates if necessary, other postemergence herbicides are most effective when weeds are less than 6 inches tall. Timing of postemergence application is therefore critical for effective weed control in non-GMO soybeans.

4. Most postemergence herbicides will cause some degree of injury to soybeans, and a second postemergence application (if needed) can further slow the growth of previously injured soybeans. So, try to avoid a program consisting of multiple postemergence applications. Use of a two-pass herbicide program that includes residual herbicides will limit the need for “rescue” applications late in the season.

5. Giant ragweed can be extremely difficult to control with a total preemergence or total postemergence program in non-GMO soybeans. Problems here include: some of the giant ragweed may be ALS-resistant; application too early results in poor control of later-emerging giant ragweed; application too late results in poor control of large giant ragweed and possible yield loss due to weed interference.

6. Lambsquarters can be difficult to control with postemergence herbicides in non-GMO soybeans. HarmonyGT and Raptor are the only postemergence herbicides that control lambsquarters, and neither controls large lambsquarters well. Both herbicides are also among the more injurious to soybeans, which can limit tank-mixing possibilities.

7. Perennial weeds are not effectively controlled by most postemergence herbicides, and should be controlled in the previous crop if possible.

Recommendations for herbicide programs in non-GMO soybeans:

* We strongly suggest use of a preplant/preemergence (PRE) followed by postemergence (POST) approach in non-GMO soybeans. Total PRE programs should be used only in fields that have low annual grass populations and extremely low populations of giant ragweed, annual morningglory, and cocklebur. In addition, do not use total PRE programs in fields with ALS-resistant common or giant ragweed or perennial weeds. Total POST programs should be used only in fields with low weed populations.

* In a PRE followed by POST program, the PRE herbicide should provide residual activity on the more problematic weeds that are in the field, such as ragweeds, lambsquarters, nightshade, and marestail. Residual activity on grasses is less of a concern due to the effectiveness of POST grass herbicides (Select, Fusion, Poast), but PRE products that suppress grasses early in the season can be advantageous in heavy grass pressure.

* In no-till soybeans, the PRE should provide effective burndown of emerged weeds before soybean emergence. Where possible, apply at least one week before planting and include 2,4-D ester. Use of glyphosate may not be necessary in the burndown if applied early enough in spring, but should be used in all fields with dandelion, Canada thistle, and where weed size requires.

* Where the field received an herbicide application the previous fall, it is still advisable to apply a burndown treatment before soybeans emerge. In this situation, the weed population at the time of planting will consist primarily of small weeds that emerge in March or April. These can be controlled with 2,4-D alone, a low rate of glyphosate, or a combination of 2,4-D with residual herbicides.

* Increasing the 2,4-D rate to 1 lb/A can improve burndown of marestail, dandelion, and other tough winter weeds. This rate must be applied at least 30 days before planting with the exception of Weedone 650 and E-99, which can be applied at 1 lb/A (1 1/3 pts of a 6 lb/gal formulation) up to 15 days before soybean planting.

* In fields that have been primarily nonGMO soybeans or a rotation of nonGMO soybeans with corn over the past four or five years (or in any field that is known to contain ALS-resistant weeds), be extremely cautious about relying on ALS inhibitors (FirstRate, Classic, Synchrony, Raptor) for POST control of common or giant ragweed. Consider use of Flexstar or a combination of Flexstar with reduced rate FirstRate, Cloassic, or Synchrony in these fields.

* Use a PRE followed by POST approach for control of giant ragweed. PRE herbicides with activity on giant ragweed include Scepter, Backdraft, Canopy XL, FirstRate, and Gangster. All of these herbicides contain ALS inhibitors, so the POST component should not rely solely on FirstRate, Classic, Synchrony or Raptor, which are also ALS inhibitors. We suggest either Flexstar or Cobra be used in the POST treatment to control giant ragweed that escape the PRE treatment (Flexstar has been more effective and less injurious to soybeans than Cobra in OSU research). A reduced rate of FirstRate, Synchrony, or Classic can be mixed with the Flexstar to improve control of large plants, but we suggest using close to the full rate of Flexstar in order to adequately control ALS-resistant plants. Keep in mind that Flexstar should be applied when ragweed plants are no more than 4 to 8 inches tall for most effective control.

* Consider a PRE followed by POST approach for lambquarters, which can be difficult to control with either of the two POST herbicides that can be effective in normal soybeans - Harmony GT and Raptor. Most PRE herbicides will effectively control lambsquarters through the growing season. The only PRE soybean herbicides that do not control lambsquarters are Dual II Magnum, Outlook, alachlor, Axiom, and low rates of Domain and Boundary. In triazine-resistant areas Sencor, Domain, Boundary, or Axiom will not control lambsquarters.

* In fields with marestail, make sure the burndown effectively controls emerged plants, and include herbicides with residual activity on marestail if applied before the 2nd week of May. Do not rely on FirstRate, Classic, or Synchrony to control plants that emerge after planting or escape burndown treatments, since ALS resistance is present in many marestail populations. The most effective residual herbicides for control of marestail, including ALS-resistant, are Sencor, Valor, Gangster, Authority, and higher rates of Canopy XL. Where the marestail are not ALS-resistant, FirstRate or Python can be used for residual control.

Use Of 2,4-D Ester In No-Till Corn And Soybean Programs

Authors: Mark Loux

The inclusion of 2,4-D ester in preplant burndown programs can greatly improve control of tough weeds and reduce the risk of herbicide resistance. Adding 2,4-D to glyphosate in no-till soybean burndown treatments would greatly alleviate the problems with marestail and dandelions that are occurring in many fields. Some guidelines for the safe and effective use of 2,4-D:

-Use 2,4-D ester products in burndown treatments, and avoid use of 2,4-D amine products. Safe use of 2,4-D ester in no-till soybeans is based on the fairly rapid degradation of 2,4-D in soil, and the low water solubility and immobility in soil of ester formulations, which results in most of the 2,4-D staying on the soil surface. The combination of these means that, when applied far enough ahead of soybean planting, 2,4-D will not reach the seed zone in concentrations sufficient to affect germination or seedling development. When applied too close to the time of planting, the risk of injury increases, especially when heavy rain occurs soon after planting or the seed furrow fails to close. 2,4-D amine formulations are much more water soluble and mobile in soil, and they should be avoided due to increased risk of injury. The same principles apply to preplant corn treatments, but corn has much greater tolerance of 2,4-D compared to broadleaf crops, so the risk of injury is reduced.

-The most common 2,4-D ester products are either 4 or 6 lb/gallon formulations. For the equivalent of 0.5 lb active ingredient per acre, use 1 pint of 4 lb/gal or 2/3 pint of 6 lb/gal product. For the equivalent of 1.0 lb active ingredient per acre, use 2 pints of 4 lb/gal or 1 1/3 pints of 6 lb/gal product.

-In soybeans, a 2,4-D ester rate of 0.5 lb/A must be applied at least 7 days before planting. For most products, a rate of 1.0 lb/A must be applied at least 30 days before planting. Exceptions are Weedone 650 and E-99, which can be applied at a rate of 1.0 lb/A as late as 15 days before planting. The higher rate can improve control of dandelion, marestail, wild carrot, and other tough winter weeds, even in a mixture with glyphosate.

-Labels vary with regard to use of 2,4-D relative to corn planting. Labels for a number of products, including Weedar and Weedone, recommend application either 7 to 14 days before corn planting or 3 to 5 days after planting (before the corn has emerged when using preemergence rates). Labels for other products allow application anytime after planting.

-Corn injury can occur when 2,4-D ester is applied at the time of corn planting, especially when combined with acetamide grass herbicides (Harness, Dual, Outlook, Define, etc). Injury is most likely to occur in coarse-textured soils with low organic matter content, and when above-average rainfall and prolonged soil moisture occur within a week after planting.

-While there are probably few differences among 2,4-D ester formulations with regard to effectiveness, some of the newer “solventless” 2,4-D ester products may be more compatible with other herbicides in tank mixtures.

Using Skip-Rows for Pest Management in Soybeans

Authors: Ron Hammond, Jim Beuerlein, Anne Dorrance, Bruce Eisley

There are several potential pest problems that soybean growers have now or will likely have in the near future. The soybean aphid was a very serious pest problem in some Ohio soybean fields in 2001 and 2003. Most of the problem fields were sprayed for this insect in late July or August, well after the soybean canopy had closed. A future concern for growers is the anticipated arrival of soybean rust, which must be managed with fungicide applications during this same time period. Soybean producers will need to choose between aerial and ground application, knowing that ground equipment will run down soybean rows and that an aerial applicator may not be available when needed..

Mid-to-late summer spraying with ground equipment will cause a yield loss if soybean plants are run down. Fortunately, most commercial sprayers have narrow tires such that only two rows are run down as the sprayer crosses a field planted in 7.5-inch rows. The following table shows the yield loss caused by different size sprayers assuming two rows are lost with each pass across the field and a potential yield of 50 bu/acre.

SprayBoom Width (ft)
#of Rows per pass
Dollars per Acre Loss
@ $ 7.50/ bu Soybeans

The yield and income losses in the table can be avoided with the use of skip rows. Numerous soybean row spacing studies indicate that for soybeans planted the first three weeks of May, the yield difference between 15-inch and 7.5-inch rows varies from no difference to about two bushels per acre depending on soil type, weather, and plant growth. Thus, leaving two rows unplanted with each pass of a 30 foot drill would cause a yield loss of only 4.2% of one bushel per acre which is worth $0.32 per acre. That very small loss is due to only 4.2% of the row middles are 15 inches wide. If the cost of seed per acre is $35.00, then the savings for not planting the two rows is $1.47, which more than offsets the yield loss due to leaving skip rows.

The bottom line is: Running down two rows with a 60 foot sprayer in August will cause a yield loss of $7.80 if soybeans are selling for $7.50 per bushel. Leaving two skip-rows with a 30-foot wide drill would increase profit by $1.15 per acre ($1.47 - $0.32). Therefore, using a skip-row system would generate $8.95 more income per acre than destroying two rows of crop by spraying in August. The economics are very similar for high yield wheat.

Soybean growers who have experienced economic losses from the soybean aphid and those concerned about soybean rust should consider looking into use of skip-rows. Extension FactSheet AGF-131-01 on the subject of

Archive Issue Contributors: 

State Specialists: Pat Lipps & Dennis Mills, (Plant Pathology), Peter Thomison (Corn Production), Mark Loux (Weed Science), Jeff Stachler (Weed Science), Bruce Eisley (IPM) and Ron Hammond (Entomology); District Specialists: Ed Lentz (Agronomy); Extension Agents: Roger Bender (Shelby), Steve Foster (Darke), Greg La Barge (Fulton), Mark Keonig (Sandusky),and Harold Watters (Miami).

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.