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Agronomic Crops Network

Ohio State University Extension


C.O.R.N. Newsletter 2005-02

Dates Covered: 
January 25, 2005 - February 8, 2005
Harold Watters

Best Equipment Strategies to Fight Against Soybean Rust

Authors: Erdal Ozkan

There are no soybean varieties currently available that have high levels of resistance to soybean rust. This leaves us with only one alternative option: spraying fungicides that are registered to control this disease. However, regardless of which fungicide is used, an effective job of controlling the disease is questionable if the fungicide is not applied properly with the most effective application strategy.

Calibrate sprayers frequently to make sure the right amount of chemical recommended on the label is applied. Too little fungicide results in poor control and reduced yields, while too much wastes dollars and increases the risk of polluting the environment. How uniformly a fungicide is applied to the plant is just as important as applying the right amount -- both of which can be achieved by using the right equipment at the right time and as accurately as possible.

The single most important factor affecting the outcome of the fight against this disease is to get a thorough coverage of the plant with the fungicide. Research has shown that there is a very strong correlation between coverage and efficacy. We have the technology to achieve this, but it may come with a higher equipment cost.

Soybean rust first shows its symptoms usually in the lower parts of the plant and works up towards the top of the plant. Detecting the disease early and using the most effective control mechanism are keys to controlling this disease. Complete coverage of the disease could be even more challenging if the symptoms of the disease are found at later stages of plant growth when the plant is close to having the full canopy. Air-assisted spraying may help in facing those challenges. A commercial-scale sprayer with air assistance may add from $10,000 to $15,000 to the price tag of the equipment, but this added cost may well outweigh the income lost due to soybean rust in one growing season.

Here are some specific recommendations to help achieve the best coverage and control when spraying for soybean rust.
- Keep spray volume above 15 gpa for best results.
- Choose the appropriate size and type of nozzles and operate them at a pressure that will allow them to produce small to medium-size droplets (200-300 microns).
- Nozzles producing a flat-fan pattern seem to provide better coverage than the nozzles producing cone pattern when spraying for soybean rust when there is full canopy.
- Choose "low-drift" nozzles, which allow a grower to increase the pressure without increasing the number of small, drift-prone droplets (those at 100 microns or smaller). Operate these nozzles at slightly higher pressures (60-70 psi) than usual. Higher spray pressures usually help the droplets penetrate the canopy better.
- Use directed spraying, if applicable, to improve coverage.
- Use twin nozzle/pattern technology. Research has shown that two spray patterns, one angled forward and one angled backward, perform better than single nozzles spraying in one direction.
- If economically feasible, use air-assisted spraying. Research has shown that air-assisted spraying, which uses air to help droplets (100 microns or smaller) reach inside of the plant canopy and underside of leaves, consistently provides the best coverage and droplet penetration, especially when beans are at or near their full-growth stage. One should match air flow to canopy density when using air-assisted sprayers.

Herbicide programs for non-GMO soybeans

Authors: Mark Loux

We continue to receive questions about herbicide programs for non-GMO soybeans. The good news – it is possible to effectively manage weeds in non-GMO soybeans. The bad news – effective control probably requires $35 to $45 of herbicide depending upon the weeds present. Some of the issues for weed control in non-GMO soybeans are:

- 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 non-GMO soybeans over the past several years.

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

- Most POST herbicides will cause some degree of injury to soybeans, and a second POST application (if needed) can further slow the growth of previously injured soybeans. So, try to avoid a program consisting of multiple POST applications at full rates, or one that requires POST rescue treatments.

- Giant ragweed is extremely difficult to control with a total PRE or total POST program in non-GMO soybeans (or in a glyphosate/2,4-D burndown followed by POST program). 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.

- Planting non-GMO soybeans into a weed-free seedbed is essential, since POST herbicides will not adequately control typical spring no-till weeds. No-till non-GMO soybeans therefore require an effective preplant burndown treatment.

Our recommendations for herbicide programs in non-GMO soybeans are as follows:

- We strongly suggest use of a preplant/preemergence (PRE) followed by 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 (almost none) of giant ragweed, annual morningglory, and cocklebur. In addition, do not use total PRE programs in fields with ALS-resistant ragweeds or perennial weeds.

- 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 Plus), 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, since mixtures of Sencor plus 2,4-D, Canopy plus 2,4-D, etc can control small weeds. Mixing glyphosate plus 2,4-D ester with the PRE herbicide will provide the most broad spectrum and consistent control.

- In conventional tillage soybeans, a PRE followed by POST program is not as critical. However, if significant populations of lambsquarters and giant ragweed occur in the field, a planned two-pass program will provide the most effective control in conventional tillage fields.

- 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 as discussed previously before grasses emerge and broadleaf weeds reach 4 inches in height.

- Increasing the 2,4-D rate to 1 lb/A (1 quart of 4 lb/gal ester formulations) 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 non-GMO soybeans or a rotation of non-GMO soybeans with corn over the past four or five years, be extremely cautious about relying on ALS inhibitors (FirstRate, Classic, Raptor, Synchrony) for POST control of ragweeds. Consider use of Flexstar or a combination of Flexstar with reduced rate of an ALS inhibitor in these fields.

- Use a PRE followed by POST approach for control of giant ragweed. PRE herbicides with activity on giant ragweed include Scepter, Canopy XL/EX, FirstRate/Amplify, 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 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 species. Keep in mind that Flexstar should be applied when ragweeds are no more than 4 to 8 inches tall for most effective control.

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

- In fields with marestail, make sure the burndown effectively controls emerged plants, and include herbicides with residual activity on marestail when applied before the middle of May. Do not rely on FirstRate or Classic to control plants that emerge after planting or escape burndown treatments, since ALS resistance is present in many marestail populations. Sencor, Valor, and Gangster are the best choices for residual marestail control due to the presence of ALS resistance in many marestail populations.

Most Recent Findings of OSU Herbicide Resistance Screens

Authors: Mark Loux

Five new marestail populations were collected during the 2004 growing season from the following counties: Crawford, Darke, Hancock, Sandusky, and Seneca. These populations were treated in the greenhouse with glyphosate at 0.75 and 3.0 lb ae/A, and also with FirstRate at 0.9 oz/A.

The results indicate the presence of glyphosate-resistant marestail in Darke and Hancock Counties. This brings the total number of Ohio counties with confirmed glyphosate-resistant marestail populations to 20. The Darke County population was near Union City and the Hancock County population was near Vanlue. Both of these populations appeared to have a slightly increased level of resistance compared to another known resistant population, but both were sensitive to FirstRate. Therfore, no additional confirmed cases of multiple resistance (glyphosate plus ALS resistance) are present in Ohio at this time. However, Purdue University has confirmed several multiple resistant populations in southeast Indiana and one population south of Fort Wayne, Indiana.

The Sandusky and Crawford County populations were confirmed to be ALS-resistant, but not glyphosate resistant. However, the Crawford and Seneca County populations had lower sensitivity to glyphosate compared to a known sensitive population. This may mean that under poor environmental or stressful conditions, plants in these populations may be able to survive a typical use rate of glyphosate, although they are clearly not glyphosate-resistant.

NutriDense Corn: Questions about Agronomic Performance and Management

Authors: Peter Thomison, Allen Geyer

I’ve received several questions recently about the agronomic performance and management of NutriDense corn. NutriDense corn hybrids have been licensed to seed companies for distribution by BASF. NutriDense corn is one of several types of specialty corn that have been developed with improved nutritional traits to enhance the feed value of corn grain. Because of the greater concentration of nutrients on a dry weight basis, feeding nutritionally enhanced grain from NutriDense corn may be a viable method to improve feed efficiency and reduce expensive fat and protein inputs for livestock producers. Contract production of Supercede corn grain might also provide growers with higher profits through premiums based on protein and oil concentration.

We evaluated NutriDense corns in 1999 and 2000 at the OSU-OARDC Research Farm at Wooster in northeast Ohio and the OSU-OARDC Northwest Research Station near Hoytville in northwest Ohio. Testing nutritionally enhanced corns is more difficult than testing conventional corn hybrids due to isolation requirements. If pollen from conventional (low oil, low protein) corn hybrids pollinates nutritionally enhanced corn hybrids, then the specialty traits may not be fully expressed. Nutridense hybrids were separated from conventional hybrid checks by at least 20 rows (50 feet) planted to a Nutridense corn hybrid to minimize pollen contamination.

Result of these evaluations can be accessed on-line.

Evaluations of Specialty Corns for Value Added Grain Production – 2000

Nutritionally Enhanced Corn Hybrids - 1999 Evaluation

Test results from 1999-2000 indicated that NutriDense hybrids were available with grain yields similar to normal corn. Severe stalk lodging was a major factor contributing to the lower yields of some NutriDense hybrids at Wooster in 2000. (I’ve been informed by seed company agronomists that the stalk quality of NutriDense hybrids used in grain production has improved since these tests were performed four years ago.)

In 2000, grain produced by NutriDense corn was characterized by higher oil content than grain of conventional corn hybrid ( 5.1% vs. 4.0 % at Hoytville, 5.5% vs. 4.3% at Wooster). The NutriDense hybrids exhibited significantly higher grain protein levels than the conventional corn. Grain protein levels of nutritionally enhanced hybrids averaged 1.9 percentage points higher than the conventional corn at Hoytville, but only 0.9% higher at Wooster. Similar differences in grain protein content were observed between test locations in 1999. Averaged across locations, starch levels in grain were 2.8 percentage points less in nutritionally enhanced corn compared to conventional corn.

A major consideration in successful production of nutritionally enhanced corn is effective use of nitrogen (N) fertilizer to ensure high yields and optimize grain protein. Effects of N application on the performance of nutritionally enhanced corn hybrids, including Nutridense corn, have received little attention. We conducted research at Hoytville, OH from 2000 to 2002 to determine effects of different timings of N application (at planting vs. split) and N rates (0, 60, 120, and 180 lb/acre) on the grain yield, protein, and oil of two corn hybrids with enhanced grain quality traits, similar to NutriDense corns. Grain protein concentration showed more consistent response to increasing N rates than did yield. Protein exhibited a linear response to increasing N rates each year. Yield responded positively to increasing N rates in two of the three years, but showed no additional response above 60 lb N/acre in 2000. Split applications of N increased grain protein concentration in two of the three years, but had little or no effect on yield. Grain oil concentration was not influenced by the timing of N application. For all N treatments, including the zero N check, oil consistently exceeded 6.0 % (dry weight basis); however grain protein was usually below 10.0% (except for the split N treatment of 180 lb/acre in 2000). Grain protein concentration, averaged across hybrids and N treatments, ranged from 7.5 to 9.4%. Relatively low percent grain protein in 2001 may be have been due to protracted wet soil conditions during the spring, which favored loss of N through denitrification and leaching. Results of the study demonstrated that N management will be an important factor in maximizing the grain protein of nutritionally enhanced hybrids, but producing grain with consistently high protein concentration may be difficult given the variation in growing conditions and environments characteristic of Ohio.

Thomison, P.R. and A. Geyer. 2005. Specialty corns for value-added grain production
Thomison, P. R., Geyer, A. B., Bishop, B. L., Young, J. R., and Lentz, E. 2004. Nitrogen fertility effects on grain yield, protein, and oil of corn hybrids with enhanced grain quality traits. Online. Crop Management doi:10.1094/CM-2004-1124-02-RS.
U.S. Grains Council. 2002. 2001-2002 value-enhanced grain quality report. U.S. Grains Council, Washington, D.C.

Northern Ohio Crops Day

Authors: Mark Koenig

February 10, 2005 is this year’s date for the Northern Ohio Crops Day that will be held at Ole Zim’s Wagon Shed, 1375 N. State Route 590 Gibsonburg, Ohio. Featured in this year’s program will be “Fertilizer Containment”, “Quadris/Warrior Study & Soybean Rust”, “Emerald Ash Borer”, and “Soybean Aphids” plus other topics that will be of interest to area producers. Private pesticide credits will be offered to fulfill the re-certification requirements for Core and Categories 1 & 9. Commercial pesticide credits for Core, Categories 2A, & 2C will also be offered. There will be a charge for Pesticide Re-certification Credits. The program has been approved for CCA continuing education units for Nutrient Management and Pest Management.

The meeting starts at 8:30 a.m. and continues until 3:00 p.m. Lunch will be provided courtesy of the Northern Ohio Crops Day Exhibitors. The program is a joint effort of Ottawa, Wood, and Sandusky County Ohio State University Extension. Please call Sandusky County office (419) 334-6340 with any questions.

Crop Profit Game Feb 15 Broadcast Features Rust Update

Authors: Greg LaBarge

The final installment of the Crop Profit Game will be held on Tuesday, February 15th from 7-9:30 pm. The program has something for everyone producing corn, soybeans and wheat in the state of Ohio. Whether you want the latest on marketing or the latest on soybean rust and aphids this program will bring you up to date. The two previous programs have been well received and found to be very valuable to the audience attending at over 40 OSU Extension Offices that provided the program in December and January. The February 15th program has generated a lot of interest with a live program update on Soybean Rust.

The February 15th broadcast will be expanded to provide the latest on the increasing information data base for soybean rust biology and management for 2005. Anne Dorrance will be returning from several national meetings with the latest on this disease and it’s control measures, so Ohio producers can make sound economic decision going into the next growing season.

The complete agenda includes the following topics:
- Grain Marketing Outlook and
- Using Crop Revenue Coverage in Developing a Grain Marketing Plan,
- Evaluating harvest date and plant population effects on corn standability and final yield,
- Wheat Fungicide/Growth Staging,
- Soybean Aphid: Current Thinking for 2005,
- Soybean Rust: What to Expect in 2005!

Ohio residents have three ways to view the programs. Many OSU Extension offices are making the program available. Call your local Extension office or visit for details.

Options exist for those who want to view the broadcast at home via Dish Network Satellite or Internet streaming video. Cost for these at-home options are $30 in-state or $50 out-of –state for the series of three broadcasts. Requirements and registration information are available at or by contacting Greg LaBarge at (419) 337-9210, or e-mail

Fungicides for Soybean Rust – Lesson 1 Some Basics

Authors: Anne Dorrance

If soybean rust makes it through the next 6 weeks in Louisiana, Mississippi and Florida, then we will need to prepare for its arrival in Ohio. Since we are all house bound or office bound with the cold and snow, I thought now would be a good time for a mini-fungicide lesson.

If soybean rust does arrive, it will be on a southerly storm via rain/wind. The spores will be dispersed across our fields and those that land in the canopy and that have 6 or more hours of leaf wetness will likely be successful in forming lesions. First the spore must germinate, then penetrate the leaf, form mycelium as it invades the leaf, then form the next structure (uredinia) which form more spores. A mini-disease cycle for one lesion.

Fungicides have different types of activity in relation to what they stop the fungus from doing in the mini-disease cycle (from spore to lesion).

Chloronitriles is the group of compounds sold as chlorothalonil, Bravo and Echo. This group of compounds is active on the spore only and must be applied prior to any rust spores arriving in the field. These materials have been widely used by vegetable producers and have proven to be a very good protectant/preventative treatment. The main limitation of this group of fungicides is that they must be applied every 7 to 10 days and are subject to weathering from rains.

Strobilurins are also protectants/preventatives. These products must also be on the plant prior to spore arrival. The two products labeled for soybean rust, Headline and Quadris, state on the label that these products are not to be used if there is more than a 3% level of disease in a field. In addition, these products can only be used once in a season for rust management.

Triazoles are curatives. There are a number of triazole products that currently have Section 18 status in Ohio for 2005, including: Bumper, Folicur, Laredo, Propimax, and Tilt. The Domark label is still pending EPA approval. These products all act on the mycelium of the rust fungus. So they need to be on the plant very soon after spore deposition in a field to have the most activity. If the triazoles are applied too early – and spores do not arrive for 15 days – then they will not have as good of activity.

Premix or combination products – One product, Stratego, has a Section 18 label for 2005 and a second, Quilt, is pending. These two compounds both have a strobilurin plus a triazole. These give the fungicide product much broader activity to kill spores as they land on new tissue and the curative action for spores that have already germinated.

Resistance management - Triazoles also have limitations, in that they cannot be used in successive sprays due to the risk of this rust fungus becoming resistant. In other words, if you are in a situation where more than one application will be needed, you cannot use a straight triazole twice. The first application should be a strobilurin or chloronitrile – and the second application a triazole OR if a triazole was first then a combination product (strobilurin + triazole) can be used for the second application. The premix or combination products can be used in successive sprays if necessary. Pricing and availability of product may play a significant role in which materials you choose to use in the event that the rust fungus does make it to Ohio.

I’ve gotten lots of questions about systemic movement and length of protection. Systemic activity is how much movement inside the plant these materials have. They are not all equal and some of these materials will require an adjuvant to penetrate the leaf. However, none of these materials are such that you can apply to the top of the plant and expect the fungicide to get to the bottom. It just isn’t going to work that way – so most of these have moderate abilities – they can move in the leaf that the fungicide hit. In addition all of them have different residuals – this can best be seen by the days required between the sprays.

Finally on these fungicides – one of the things to really key into – is the preharvest interval. For all of these materials, it is quite long. For the chloronitriles – days to harvest is 42 while for the strobilurins it is 21 days and for most of the triazoles it is 28 days. So for the April/May planted beans – we will be out of the fields by early to mid-August depending on location in the state and maturity group. In other words, if rust arrives in Southern Ohio at the end of August – there isn’t anything we will be able to spray at that time.

I fully realize that this may generate more questions than answers – but we will continue with this series regularly in C.O.RN. and do have your questions ready for the February 15th, Crop Profit Game satellite conference. To attend, see for a County Extension office location near you.

Archive Issue Contributors: 

State Specialists: Anne Dorrance and Dennis Mills (Plant Pathology), Ron Hammond (Entomology), Mark Loux and Jeff Stachler (Weed Science), Erdal Ozkan (Ag Engineering), Peter Thomison and Allen Geyer (Corn Production), Robert Mullen (Soil Fertility) and Ed Lentz (Agronomy). Extension Agents and Associates: Roger Bender (Shelby), Howard Siegrist (Licking), Dusty Sonnenberg (Henry), Todd Mangen (Mercer), Steve Bartels (Butler), Glen Arnold (Putnam), Greg LaBarge (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.