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New weed control

No big game-changing herbicide products are cleared yet this year. But Bill Curran, Penn State University Extension weed specialist, says next-generation herbicide-resistant crops are one step closer.

“LibertyLink is one of the more interesting products. But it has to be cost-competitive with glyphosate — at $2 an acre,” he adds.

His biggest concern is that farmers must be proactive on making sure herbicide-resistant weeds don’t develop. “They creep up if you’re not paying attention. After that second year, you’ll have a full-blown problem.”

The following are corn herbicide products and formulations that were newly labeled in 2009, or are expected to be labeled for use this spring in most Northeast states. This summary was put together by Curran and fellow Penn State weed specialist Dwight Lingenfelter, then reviewed by Cornell University’s Russ Hahn. Products not expected to be labeled in 2010 for New York are noted with an asterisk (*).

Key Points

• Relatively few new products are cleared for 2010.

• Several new “safeners” reduce risk of crop injury.

• New safened products often have different formulations — and rates.

New for corn

Balance Flexx 2SC* (Bayer) contains isoxaflutole plus a new “safener,” or substance that protects plants from herbicide damage, called cyprosulfamide. With this safener, it can be applied preemergence or early postemergence on corn up to the V2 growth stage. Bayer adds the safener to increase corn metabolism of isoxaflutole and reduce potential crop injury.

Capreno* (Bayer) is a post, over-the-top mix of tembotrione, thiencarbazone and the cyprosulfamide safener. Its weed control is similar to Laudis, but has broader spectrum grass control due to the thiencarbazone ALS inhibitor.

Capreno likely will be used primarily in field corn. Laudis will be targeted in the sweet corn market. Penn State research has looked at these products over the past few years and noted limited crop injury and good weed control.

Corvus 2.63SC* (Bayer) is a combination of isoxaflutole, thiencarbazone plus the new safener. This pre or early post product has a broader weed control spectrum than Balance Flexx. Its ALS inhibitor controls several grass and broadleaf weeds. Corvus can be applied either pre or early post.

Neither Balance Flexx nor Corvus will likely control severe annual grass problems (foxtail and panicum, etc.). Use in a planned pre, followed by a post program with extra grass control. They also can help with no-till burndown and provide some residual control of triazine-resistant weeds.

Prequel 45WG* (DuPont) contains two active ingredient modes of action (Balance, an HPPD inhibitor, and Resolve, an ALS inhibitor). It’s similar to Corvus, but doesn’t contain a safener, so it must be applied before corn emergence.

It provides some burndown and residual control of common broadleaves and some grasses at the labeled rate. It’ll need to be mixed with another grass herbicide or require a post program to control escaped weeds.

For corn and soybeans

Ignite 280 2.34SL (Bayer), formerly known as Liberty, now has a new higher-load glufosinate formulation. This broad-spectrum post herbicide controls many annual broadleaf and grassy weeds and suppresses some biennials and perennials.

Since it’s a contact herbicide, it’s weaker than glyphosate on perennials and on grasses such as yellow foxtail, shattercane and barnyard grass. But it’s more effective on broadleaves such as annual morningglory, eastern black nightshade and smartweed.

Weed size is more critical with Ignite — 4 to 6 inches tall, maximum. Warm temperatures, high humidity, bright sunlight and uniform coverage improve its performance. Again, it doesn’t have residual activity and won’t control weeds not yet emerged.

This product can be used on all LibertyLink corn and soybean varieties, and has limited burndown uses. A pre or post application with a residual product may be needed for broader spectrum and extended control in problematic fields.

For more consistent lambsquarters and velvetleaf control, apply between dawn and two hours before sunset. In studies at Penn State and other universities, some occasional temporary crop injury was observed to soybean; however, no yield reductions were observed.

In LL corn, Ignite can be applied over the top to corn up to 24 inches tall. In LL soybeans, it can be post-applied from emergence to just before bloom.

Ignite and the LL system will be marketed as a rotation alternative to a glyphosate-resistant system, for reducing potential of glyphosate-resistant weed biotypes.

Kixor* (BASF) has a new active ingredient called saflufenacil. It’s a PPO-inhibitor herbicide, as are Valor and Authority. In this region, Kixor’s potential has been focused as burndown for glyphosate-resistant horseweed or marestail in no-till soybean, and as a new corn preemergence mode
of action.

Kixor-powered products will provide burndown and residual activity on summer annuals, including pigweed, lambsquarters and nightshade. Our colleagues to the south found mixed results on horseweed.

Kixor won’t control grasses. It’ll need to be tank-mixed with other products or applied post to control escaped weeds or to increase the control spectrum.

BASF developed prepackaged mixtures to meet this need: Sharpen (Kixor alone), Integrity (Kixor and Outlook), and Optill (Kixor and Pursuit). They’ll primarily be used as pre, “setup” herbicides since they’ll typically be used in a planned pre followed by post herbicide program.

Sharpen can be used in field corn, soybeans or small grains. Integrity, as a corn burndown pre, provides some annual broadleaf and grass residual activity. But at labeled rate, post herbicides will likely be needed to control escapes. In soybeans, it’ll likely need to be followed by glyphosate or other post herbicides.

A note about DuPont Q safeners

DuPont Q herbicides (Steadfast Q, Resolve Q and Accent Q) contain the isoxadifen safener. The company claims this safener allows more application flexibility across diverse conditions.

It doesn’t totally eliminate potential crop injury, but does lessen the impact. And as Russ Hahn reports, “Effects of the safener can be dramatic when Q products are used on short-season hybrids compared with applications made without safener.”

These are similar to their nonsafener counterparts. They can be tank-mixed and applied post with glyphosate or Ignite, or included in other post programs.

Remember, though, that Q herbicides are formulated at different concentrations than their sister products. Steadfast, for instance, is a 75WG and is typically applied at 0.75 ounces per acre. Steadfast Q is formulated as a 37.7WG and needs to be applied at 1.5 ounces per acre.

Accent 75WG and Accent Q 54.4WG also have different application rates. Both can be applied to certain sweet corn varieties.

Resolve is single-ingredient rimsulfuron. But Resolve Q is rimsulfuron and thifensulfuron (Harmony’s active ingredient) and the Q corn safener.

This article published in the February, 2010 edition of AMERICAN AGRICULTURIST.

All rights reserved. Copyright Farm Progress Cos. 2010.