Roundup Ready Alfalfa Deregulated

Roundup Ready Alfalfa is once again nonregulated and will be available to plant as another option for forage growers. Below is the statement from the USDA Animal and Plant Health Inspection Service:

On January 27, 2011, APHIS announced its decision to grant nonregulated status for alfalfa that has been genetically engineered to be resistant to the herbicide commercially known as Roundup. The final Environmental Impact Statement (EIS) for Roundup Ready® Alfalfa (RR alfalfa) was published on December 23, 2010. APHIS was required to wait at least 30 days after the EIS was published in the Federal Register before issuing its decision. APHIS made its decision after conducting a thorough and transparent examination of alfalfa through a multi-alternative EIS and several public comment opportunities, and determining that RR alfalfa does not pose a plant pest risk.

APHIS prepared the EIS to comply with a February 2007 judgment and order by the United States District Court for the Northern District of California. APHIS originally deregulated the lines of RR alfalfa in June 2005 and a lawsuit was subsequently filed. The judge vacated APHIS’ 2005 decision to deregulate RR alfalfa and determined that the Agency must prepare an EIS in support of a regulatory determination regarding RR alfalfa.

Taken from the USDA APHIS Website at  Febraury 18, 2011.

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Roundup Ready Corn – Avoid Yield Losses Due to Weeds

The following is a reprint of an article from the Ag Answers website (Purdue and Ohio State Universities Joint project) on glyphosate application timing and potential for yield losses in Roundup Ready Corn.

As more producers choose Roundup Ready corn they might have to become accustomed to the unfamiliar sight of weeds at crop emergence, said Bill Johnson, a Purdue University weed scientist. In addition to their unsightliness, the weeds could take valuable nitrogen away from the corn, resulting in yield losses.

In many conventional corn systems, producers apply atrazine-based herbicides before the crop is planted, thereby keeping weeds at bay until the corn is several inches high. With Roundup Ready corn, some farmers are likely to abandon these preplant soil-applied herbicides and spray Roundup later in the season, Johnson said.

“In a system where we don’t use soil-applied herbicides we’re going to have weeds emerging with the corn,” Johnson said. “If there is nitrogen in that field, weeds will utilize it and enhance their growth rates early in the growing season. The weeds could become very competitive with the corn.

“Essentially, we could be fertilizing the enemy, giving it a competitive advantage and allowing it to grow more quickly, which may cause it to outgrow the Roundup technology that we’re using to control it if we have a prolonged period of wet weather after planting that keeps the sprayers out of the field.”

Research conducted by Johnson indicates that annual grass weeds such as foxtail, crabgrass and fall panicum are adept at absorbing nitrogen. “We find that early in the year grass weeds take up nitrogen at approximately the same rate as corn,” Johnson said. “That continues until the grass weeds are about 4 inches tall, and then the weeds go into a period where they accumulate nitrogen very rapidly — more rapidly than corn at that point. By the time the weeds are a foot tall, if you look at the amount of nitrogen in grass on a per-area basis, they can contain three times as much nitrogen as the corn can at that time.” Weeds don’t have to take up much nitrogen to cut into corn yields, Johnson said.

“It does appear that there is a relatively low threshold level of nitrogen that can be present in grass weeds to cause yield losses,” he said. “What we have seen in our research across a number of different weed species is by the time the weeds have between 10 pounds and 20 pounds of nitrogen per acre in their above-ground biomass, that appears to be a threshold level at which we start seeing yield reduction in corn. We’ve observed that across foxtail, shattercane, and giant ragweed infestations.

“If you have that much nitrogen in the above-ground biomass, you probably have about that much in the below-ground biomass, as well. So we may be representing only about half the amount of nitrogen that’s in the weeds.”

Farmers who plant Roundup Ready corn need to make timely applications of the herbicide in order to prevent possible yield losses, Johnson said.

“A Roundup Ready system can be very effective but the importance of the proper application timing of glyphosate — or Roundup — is going to be much more important in corn than it is in soybeans,” he said. “In corn if we miss that optimal application window by just a couple of days we’re looking at a 1-2 bushel yield loss per day.”

Annual grass weeds should be controlled before they reach 4 inches in height, or about 23 days after planting when corn is at the V2 to V3 leaf stages, Johnson said.

Other strategies for controlling early season grass weeds in Roundup Ready corn include:

* Continue using soil-applied residual herbicides — “For atrazine premixes, utilizing anywhere from about a one-half to full labeled rate at or slightly before planting and then following up with glyphosate post-emergence, is very effective,” Johnson said.

* Perform two post-emergence applications of Roundup — “Target the first application when grass weeds are 3-4 inches tall and make a second application before corn has eight collars or is 30 inches tall,” Johnson said. “This strategy is less desirable than using a soil-applied herbicide followed by glyphosate because we’re putting a lot of selection pressure out there for glyphosate-resistant weeds. This strategy also depends on your ability to get over your corn twice with a sprayer.”

Farmers should scout their fields 2-3 weeks after an initial post-emergence herbicide treatment, Johnson said. “Get into the field and pull back some of the residue and see if weeds are germinating,” he said. ” Remember that the first application of glyphosate will not provide any residual activity on weeds unless it is tank mixed with another herbicide that has residual activity.”

Go to for the full article.

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Getting the Most out of Glyphosate Applications

Roundup Ready corn is being sprayed across Delaware now and full season soybeans will not be far behind. The following is a good article on getting the most out of your glyphosate sprays (active ingredient in Roundup).

Postemergence herbicide applications for weed control in Roundup Ready corn are going on now and full season Roundup Ready soybean sprays will be quickly approaching. There are several things that should be considered to maximize weed control with glyphosate from these applications in Roundup Ready crops. Following these guidelines can help reduce the risk of glyphosate failures, as well as reduce the chances of lower crop yields due to weed competition.

Glyphosate formulations

There are over 30 different glyphosate products that growers can choose from for weed control in glyphosate-resistant crops. With all of these choices, it is important to keep in mind that not all glyphosate formulations are created equal. Knowing your glyphosate product is essential to achieving optimum weed control. There are two main differences in the many available glyphosate products. Glyphosate products can differ in the concentration of glyphosate acid in the formulation (glyphosate acid is what kills the weed). This concentration is expressed as pounds acid equivalent per gallon (lb a.e./gal). Different glyphosate concentrations will change the amount of product used for the various formulations. is a compiled list of several glyphosate products and the product use rates for equivalent amounts of glyphosate acid per acre.

Another difference in glyphosate products is whether a surfactant needs to be added to the spray solution or if the formulated glyphosate product has a built-in adjuvant package. Products like Roundup PowerMax, Touchdown Total, and several others have built-in adjuvant systems. Even though all of these products have a built-in adjuvant system, there can and many times are differences in the type of surfactant formulated in the product. These differences may equate to differences in weed control under extreme conditions. However, under most conditions there are no differences between these products especially when they are used at the correct rates, at the appropriate application timings. For products where the addition of a surfactant is recommended add a high quality non-ionic surfactant at 0.25 to 1.0 percent v/v. Table 10 also includes information on whether the addition of a surfactant is recommended for a particular glyphosate product.

Addition of ammonium sulfate

Ammonium sulfate (AMS) should always be added to all glyphosate products. We recommend adding dry spray grade AMS at 17 lbs/100 gal. or the equivalent of 17 lbs/100 gal. of liquid AMS products. The addition of AMS minimizes the negative effect of hard water on glyphosate activity and is important for velvetleaf control, regardless of water quality.

Application rate

Applying the appropriate glyphosate rate in glyphosate-resistant soybean is important for consistent weed control. Proper glyphosate rates should be based on weed type, weed size and spray volume. In most cases the appropriate rate to use for weed control in glyphosate-resistant soybean is 0.75 lbs a.e./A of glyphosate. This rate will effectively control several annual weed species between two and eight inches tall. However, if weeds become larger or harder to control, species such as common lambsquarters or giant ragweed are present, increase the glyphosate rate to 1.1 lbs a.e./A or 1.5 lbs a.e./A to adequately control these weed species. In addition, by matching the appropriate glyphosate rate to the correct weed size you reduce your chances of weed control failures under extreme conditions.

Application timing

Glyphosate application timing is everything. It is important to make timely glyphosate applications to minimize the chances of yield loss due to early-season weed competition and to maximize weed control. The optimum time for glyphosate applications is when weeds are four inches tall in narrow-row (7.5 and 15 inches) soybean and six inches tall in wide-row (30 inches) soybean. Controlling weeds at these times reduces the chances for soybean yield loss, as well as reduces the risk of weed control failures of larger weed that may be under stressful conditions (drought, stem-boring insects, coverage issue, etc.). For corn, early weed competition will reduce yields so it is best to have a residual herbicide to help control early weeds and use the glyphosate to control escapes once the majority have emerged unless fields have very low weed pressure. Heavy grass pressure early is a particular problem because grasses take up considerable nitrogen. If a total post program is used then time when a large majority of the weeds have germinated and add some residual materials or plan on a 2 pass system with glyphosate early and then late to catch escapes.

Application technologies

Windy conditions in the narrow application windows that we see this time of year make the use of drift reducing nozzles or drift reducing agents almost a necessity to reduce or prevent off-site particle drift. When using these technologies it is important to know their limitations. Using these technologies without the proper spray pressure and spray volumes can lead to reduced weed control with glyphosate. To maintain effectiveness with these technologies make sure to follow manufacturer’s recommendations on pressure and volume, apply the appropriate glyphosate rate for the target species, and always check for a uniform spray pattern. Combinations of some of these technologies can reduce spray coverage that may result in reduced weed control. Following these guidelines, particularly checking the spray pattern, can help determine if the weeds are receiving an adequate dose of the herbicide for weed control.

Adapted from “Get the most from you glyphosate applications” by Christy Sprague, Crop and Soil Sciences, in the Michigan Field Crop Team Advisory Alert from Michigan State University. Additional information on corn from Gordon Johnson, Extension Agriculture Agent, UD.

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Glyphosate Formulations

The following is a table listing the various glyphosate products on the market for use in Roundup-Ready crops (as well as general non-selective weed control). It is important to compare the amount of active ingredient and adjuvant load when pricing glyphosate.

Click on the table for a larger image in a new window.

Information from the 2009 Corn Weed Management Guide for Delaware and New Jersey by Mark VanGessel, Extension Weed Specialist, University of Delaware and Brad Majek, Extension Weed Specialist, Rutgers University

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Controlling Weed Escapes in Roundup Ready Beans

The following is a good article on controlling weed escapes in Roundup Ready soybeans from the Ohio State University.

This is the time of year when we get phone calls about rescuing weed control in Roundup Ready soybean fields, and we hear most often about marestail, giant ragweed, and lambsquarters. Less than adequate weed control after several herbicide applications can often be attributed to failure to use the appropriate combination of herbicides and application timings for the weed population. However, adverse weather, crop replants, and slow crop development can also negatively impact weed control programs. Weeds that survive into mid-season can also be indicative of herbicide resistance, or a developing herbicide resistance problem. Before spending additional money on a late-season POST herbicide application, it’s important to consider what the goal of the application is, and whether any effective herbicide options remain based on what has already been applied this season.

For example, a marestail plant that has survived previous application of glyphosate plus an ALS inhibitor (FirstRate or chlorimuron) is not likely to be controlled by additional herbicide applications. A late-season application that does not control marestail will also fail to suppress it enough to make harvest any easier. On the other hand, small soybeans that are infested with late-emerging marestail plants, which have not been subject to a prior herbicide treatment, may merit an additional application where the marestail is known to be still sensitive to glyphosate or ALS inhibitors. Where someone is determined to treat marestail that have survived previous application, our recommendation is typically going to be something like a full rate of FirstRate or Classic plus up to 1.5 lbs ae/A of glyphosate. The cost of this, up to $25 or more based on current glyphosate prices, has to be weighed against its possible effectiveness.

For both lambsquarters and ragweeds, it is possible that a second POST application of glyphosate will control plants that survived a previous application. However, as we have stated in previous C.O.R.N. articles, this is most likely to occur where the first application greatly suppressed the weeds (70 to 80% control at least), and the second glyphosate treatment is applied about 3 weeks of the first. Where the previous glyphosate application had little effect on the weeds, an alternative to glyphosate would be required in the second application for control of ragweeds. There are essentially no consistently effective alternatives to glyphosate for control of large lambsquarters.

Choices for ragweeds include FirstRate, Classic, Cobra/Phoenix and Flexstar, and the decision here should be based on several factors. Classic or FirstRate would generally be the most effective option where the population is known to be still sensitive to ALS inhibitors. Where ALS resistance is known or suspected, we would suggest use of Cobra or Phoenix. Use of Flexstar should generally be curtailed as we move later into the season, since it has more restrictive guidelines for crop rotation. Where the glyphosate had substantial activity on the weeds in the first application, the second application should generally contain glyphosate plus one of the alternatives mentioned here. Keep in mind the following also: 1) expectations should be lowered for late-season applications to large weeds – plant death may not occur, but harvest problems may at least be reduced; 2) maximum labeled rates of the alternative to glyphosate are likely to be needed; 3) spray adjuvants should be optimized for the alternative; and 4) spray coverage should be maximized through use of slower application speeds, higher volumes, and nozzles that provide a greater number of relatively small droplets (for example, extended range flat fans instead of ai nozzles). As stated previously, the possible merits of a late-season application to large weeds have to be weighed against the cost and risk of soybean injury.

Reprinted in part from “Late-Season POST Herbicide Applications in Soybeans” by Mark Loux in the July 14, 2008 edition of the Crop Observation and Recommendation Network newsletter from the Ohio State University.

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Improving Glyphosate Performance In Roundup Ready Soybeans

The following is a good article from Iowa State University on improving glyphosate performance in Roundup Ready soybeans.

Although glyphosate resistant weeds have been documented in other states, at this time our only confirmed glyphosate-resistant species is horseweed/marestail (Conyza canadensis). However, over the past decade we have selected for a weed spectrum that possesses a higher level of tolerance than was present at the start of the Roundup Ready era of weed management. Because of this, glyphosate control failures are more common now than they were ten years ago.

There are several ways to reduce performance issues when using glyphosate for postemergence weed control. The most important is to apply the herbicide in a timely fashion. The majority of control failures are at least partially caused by spraying weeds that exceed four inches in height. Lambsquarter, waterhemp, horseweed and giant ragweed are species where timeliness is especially critical in obtaining consistent results.

The second factor resulting in inconsistent results is too low of rate. Base the rate on the most difficult to control weed in the field. The third factor, and least understood, is the influence of environmental conditions on herbicide efficacy. Light, temperature, soil moisture, relative humidity and numerous other factors all interact to influence the susceptibility of a plant to any herbicide. Lambsquarter is particularly responsive to environmental conditions, and under certain conditions becomes almost immune to postemergence applications. Timely application to small weeds greatly reduces the impact of the environment on weed response to postemergence herbicides.

Persons who have experienced inconsistent results in the past typically are interested in additional materials to add to the tank to minimize problems. The types of additives recommended for use with glyphosate varies among products, although all glyphosate products recommend the use of AMS or other nitrogen sources. A variety of AMS alternatives (water conditioners) are marketed for use with glyphosate, but many do not provide enough active ingredient to reduce the antagonistic effects of salts present in the carrier. The specific recommendations for surfactants vary among glyphosate products and should be followed. The use of surfactants with ‘fully loaded’ formulations has not consistently overcome problems associated with spraying large weeds or weather-related issues.

In certain situations addition of a second herbicide to glyphosate may improve weed control. There should be a specific purpose for adding a second product to the tank rather than arbitrarily adding something in the hope of improving performance. Control of big giant ragweed can be improved with the addition of an ALS herbicide (cloransulam – First Rate/Amplify; clorimuron – Classic) or a PPO inhibitor (Flexstar, Phoenix, Cobra). Cloransulam, chlorimuron or a PPO inhibitor can improve the control of annual morningglories. There are no products for use in soybean that will consistently improve the performance of glyphosate on lambsquarters.

In summary, glyphosate remains the most effective herbicide we have to control weeds in soybean and corn. However, consistent results can only be obtained through good management of the product. Proper rate selection and timing of application are the most important steps.

Adapted for Delaware from “Improving glyphosate performance in Roundup Ready soybean” By Bob Hartzler, Department of Agronomy, Iowa State University in the July 7, 2008 edition of the Integrated Crop Management News from Iowa State University.

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Glyphosate Use Decisions in Soybeans

The high price of glyphosate (Roundup and many others) has Delaware farmers thinking about alternatives in soybean weed control programs. Careful thought needs to go into this decision. Certainly, glyphosate resistant weeds play a part in this decision. Cost, effectiveness, application window, weed control spectrum, and cropping system (notill vs reduced till vs clean till) will all come into play. The following is an article on the subject.

Glyphosate has been the herbicide of choice for soybean weed control for a decade and for good reason. It controlled weeds well without injuring soybeans and its price kept dropping, which made the choice easier. However, the trend of low priced glyphosate changed in 2008. Glyphosate prices have spiked because of reduced glyphosate supplies and increased demand.

Does this change how glyphosate is used in soybeans? Glyphosate will still be the backbone for most soybean weed control programs, but the higher price may have a couple consequences. First, some people may be tempted to reduce glyphosate rates, which may lead to poor control if the weeds are too large when sprayed. Some people also suggest that reduced rates may contribute to a shift towards more tolerant weeds. Regardless of price, apply the glyphosate rate that is appropriate for the weed species and size in soybean fields. Avoid the temptation of reducing rates below those needed for effective control just to save costs.

The second consequence of higher glyphosate prices is that it may open the door for some other herbicide options. Consider the preemergence (PRE) herbicides. The cost of several PRE herbicides that are recommended as foundation treatments in Roundup Ready soybeans may be similar to the current cost of glyphosate. “Foundation treatments” often refer to PRE herbicides that are applied at lower rates to provide early season weed suppression. They can help to control weeds that might be tougher to control with glyphosate alone or provide early season weed suppression so that glyphosate can be applied closer to soybean canopy closure. As a result, more consistent and higher levels of weed control are typical (based on university test results). Adding a PRE herbicide also brings another herbicide mode of action into the weed management program, which may reduce the selection pressure for glyphosate-resistant weeds.

Conditions where two glyphosate applications may be required:
• 30-inch row soybeans
• Weeds with extended emergence (ie morningglory, black nightshade)
• Tough to control weeds (ie lambsquarters)

Most of the foundation herbicide programs have been promoted to improve broadleaf weed control. Some other herbicides provide effective control of a mix of broadleaf and grass weeds while others are primarily effective on grass weeds. More information on herbicides, their use, and weed control ratings can be found in the 2008 Soybean Weed Management Guide for DE and NJ

Glyphosate is only one of many items with a rapidly changing price. The prices of crops, fertilizers, seed, fuel, and land are all in flux and it may be tempting to cut costs. However, remember that the goal of a weed management program is to protect yield. The old saying about being penny wise and pound foolish certainly applies to weed management. Herbicides are a wise investment. This investment may now include more than just glyphosate. The price increase of glyphosate should make us consider if other herbicide options have a fit in soybean systems and provide benefits to improve overall weed management.

Adapted from “Does Glyphosate Price Matter?” by Chris Boerboom, Extension Weed Scientist, University of Wisconsin, in the April 10, 2008 edition of the Wisconsin Crop Manager.

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