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The latest in weed control for 2012

What’s new in weed management for 2012? While there haven’t been any new herbicide products introduced for 2012 (as of this writing), there are several products pending registration. There are some “new” generic herbicides and changes in herbicide labels. Following is a partial list of these changes. The list is provided by Mike Owen, Iowa State University Extension weed scientist.

The latest in weed control for 2012

What’s new in weed management for 2012? While there haven’t been any new herbicide products introduced for 2012 (as of this writing), there are several products pending registration. There are some “new” generic herbicides and changes in herbicide labels. Following is a partial list of these changes. The list is provided by Mike Owen, Iowa State University Extension weed scientist. The inclusion of products should not be construed as an endorsement by ISU or exclusion considered a lack of support.

Ignite (Bayer Crop Science). The Ignite label now describes a single application dose of up to 36 fluid ounces per acre. This application can be followed by one additional application of a maximum 29 fluid ounces per acre for a seasonal maximum Ignite application of 65 fluid ounces per acre. Ignite applications to corn have not changed; the maximum amount of Ignite in any single application is 22 fluid ounces per acre, with a seasonal total of 44 fluid ounces per acre.

Vida (Gowan). Vida (pyraflufen-ethyl) is an inhibitor of the PPO enzyme and a potent contact herbicide that can be applied to soybeans and corn as a preplant burndown, at planting burndown and after planting burndown but prior to crop emergence for control of many broadleaf weeds. Vida is now registered as a postemergence-directed application in corn (conventional, glyphosate-tolerant, LibertyLink, popcorn, seed corn, corn silage, corn stover). Sweet corn is not registered for postemergence-directed application. Refer to the label for specific restrictions and directions.

Flexstar GT 3.5 (Syngenta). This is a different premix formulation of fomesafen and glyphosate. This premix contains 5.88% fomesafen and 22.4% glyphosate for a total of 0.56 pounds of fomesafen and 2.26 pounds (acid equivalent) of glyphosate per gallon product. The use rate in Iowa is 2.8 pints per acre.

Medal herbicides (Syngenta). Medal herbicides are a new S-metolachlor series of products with 7.62 pounds of active ingredient per acre (Medal and Medal EC), 7.64 pounds of active ingredient (Medal II EC) and a premix Medal II AT, which is atrazine and S-metolachlor at 3.1 and 2.4 pounds active ingredient respectively.

Warrant (Monsanto). Warrant is an encapsulated formulation of acetochlor that is now labeled for application to field corn as a postemergence application. Applications can be made until the corn is 30 inches in height, either broadcast or as a directed treatment (drop nozzles) to minimize interference of the crop with spray coverage. Warrant should be applied before weed emergence and will provide residual control of annual grasses and some small-seeded annual broadleaf weeds.

Roundup Ready Plus weed management solutions (Monsanto). Monsanto has partnered with many companies to improve weed management in glyphosate-resistant corn and soybeans, and has incentivized the addition of products other than their proprietary herbicides to provide stewardship to glyphosate and the trait. Additions to the previously listed products are Cobra/Phoenix in soybeans and Impact in corn.

Basis Blend (DuPont). This is a premix of rimsulfuron (20%) and thifensulfuron (10%), which is suggested to be a better formulation that is easier to handle, mix and clean out of sprayers than Basis 75% DF. Basis Blend can be applied any time after harvest but before ground freeze-up. It can be applied with other herbicides (2,4-D) and is registered for application to fields for corn or soybeans.

Valor (Valent). Valor has a modification of the label that describes planting corn seven days after application in no-till and minimum-till systems.

Pyroxasulfone (several). Pyroxa-sulfone is a “new” product that has been included in the ISU herbicide research program for many years as KIH-485. Considerable research was conducted on corn and soybeans and a variety of application timings (early preplant) and rates were included in this extensive evaluation. It was first included in the ISU research program in 2003 as a 3.57 SC formulation and was a Kumiai experimental product. This herbicide is an inhibitor similar to the mechanism and action demonstrated by S-metolachlor and acetochlor (Group 15). Agreements have been made with BASF, FMC and Valent to market pyroxasulfone in different proprietary products, either alone or in combination with other herbicides. These registrations are pending.

New genetically advanced traits (several). Development of new genetically engineered crop traits continues with regard to dicamba-tolerant soybeans (Monsanto) and the DHT soybean and corn (Dow AgroScience). According to these companies, these new crop traits are on track for commercialization at mid-decade. There has been discussion about the utility of these traits and labeled herbicides as tools to better manage weeds, particularly those weeds (common waterhemp) that have evolved resistance to glyphosate.

Concerns exist about the movement of the herbicides used in these genetically engineered crops to sensitive crops (such as grapes), and whether or not use of the systems will result in new resistant weed biotypes. The companies are spending considerable time and money developing stewardship programs and use guidelines in an attempt to proactively mitigate these concerns. However, it’s critically important for growers and applicators to recognize that adoption of crop systems based on these technologies have risks and limitations. These aren’t the new “silver bullet.”

DuPont is developing Optimum GAT crops, but the development has been delayed indefinitely, according to DuPont.

Summing up

While there haven’t been many truly new tools in weed control and management introduced for 2012 (as of now), some things that have occurred aren’t necessarily good, says ISU’s Mike Owen. Herbicide resistance, especially common waterhemp, has escalated for weed populations with evolved resistance to glyphosate, and resistance to HPPD herbicides has been identified in a number of locations across Iowa.

“Unfortunately, again as predicted, no new ‘silver bullets’ have surfaced and in fact, it is unlikely that new herbicide mechanisms of action will be introduced in the foreseeable future,” he adds. “Thus, it becomes much more important to recognize the tactics that are available and use a diverse, long-term approach.”

Corn herbicide receives EPA’s OK

In December, the Environmental Protection Agency granted Syngenta registration for Zemax herbicide. Zemax is powered by Callisto Plant Technology and formulated to deliver long-lasting residual weed control and application flexibility, says Johnny Reynolds, Syngenta senior group leader for herbicide development.

“Based on the same capsule-suspension formulation as Halex GT corn herbicide, Zemax combines two active ingredients (mesotrione and S-metolachlor) into one product with optimized handling and physical properties,” he says. “It has good compatibility with sulfur-containing nitrogen fertilizers and other critical tankmix partners.”

Mesotrione, the active ingredient in Callisto, provides burndown and residual broadleaf weed control, while S-metolachlor, the active ingredient in Dual II Magnum, offers residual grass and small-seeded broadleaf weed control.

Zemax has two modes of action to decrease dependence on glyphosate and controls weeds that are difficult for glyphosate, such as waterhemp and pigweed, says Reynolds. It features excellent crop safety based on the proven corn safener, benoxacor, along with application flexibility. Zemax can be applied at full rate preemergence, at a foundation rate followed by Halex GT or tankmixed with glyphosate for postemergence application up to 30-inch corn.

Mike Owen.tif

GROWING PROBLEM: Weeds are no longer being effectively controlled by glyphosate alone. But don’t just think about rotating herbicides year to year. Mike Owen, Iowa State University Extension weed scientist, says farmers need to look at their weed management with a five-year goal in mind and plan accordingly.

This article published in the January, 2012 edition of WALLACES FARMER.

All rights reserved. Copyright Farm Progress Cos. 2012.

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