New herbicides added to your weed control kit

Weed control systems expanded for 2010 if you’re using Roundup Ready or LibertyLink hybrids. Several new options are designed to help improve overall weed control in these systems.

“Most of the new products are most useful in a system that includes a postemergence broad-spectrum herbicide in corn,” says Tom Bauman, Purdue University weed control specialist.

Bauman and fellow Extension specialists Bill Johnson, Tom Jordan and Glenn Nice recently outlined what’s new in herbicide options for 2010.

Corvus. This product is labeled for soil-applied preemergence and early post applications in corn. The upper limit is V2 corn. Made by Bayer, its active ingredients include isoxaflutole (Balance) plus thiencarbazone methyl, plus a safener.

Adding atrazine helps performance, especially on ragweed, cocklebur and morningglory, Johnson says. “You’re trying to gain whatever suppression you need early. That helps preserve yield versus letting weeds get ahead of you before you make the postemergence glyphosate application.”

Key Points

• Most new herbicides work best with glyphosate or glufosinate.

• BASF adds three herbicides with Kixor technology.

• Labeled rate not always same as earlier experimental rate.

 

Sharpen. This is one of three new offerings from BASF. All contain Kixor technology. The active ingredient is new chemistry — salfufenacil plus a safener. It’s a preplant burndown and preemergence product for both corn and soybeans. Apply at 2 to 3 ounces per acre in corn and 1 ounce per acre in soybeans. At the labeled soybean rate, it suppresses broadleaf weeds and should be used with a residual broadleaf herbicide.

“We see a real fit in helping on marestail,” Johnson says. “It can take out emerged marestail up to a foot tall in three days. However, the low use rate in soybeans will limit residual control on marestail.”

It can be used with glyphosate in place of 2,4-D ahead of soybeans in a burndown mix. This combination won’t have a seven-day plant-back restriction, Johnson observes.

Optill. Also from BASF, Optill’s active ingredients are salfufenacil plus imazethapyr, the active ingredient in Pursuit. It’s preemergence for soybeans.

Any new products containing salfufenacil can’t be applied within 30 days of certain herbicides, including Authority First, Sonic, Authority Assist, Authority MTZ, Prefix, Valor, Valor XLT, Envive and Gangster.

Integrity. This is the third new offering from BASF. It contains salfufenacil plus dimethenamid, the active ingredient in Outlook. Use it preemergence in corn. Labeled rate is 10 to 16 ounces per acre. “It appears to be a very good herbicide,” Johnson notes. He’s looked at it in trials for several seasons.

The only caution is that Johnson looked mostly at experimental rates of 20 to 25 ounces per acre. He has less experience at the current labeled rate.

Prequel. It’s a soil-applied herbicide from DuPont, intended for pre-plus-post herbicide programs in corn. Active ingredients are isoxaflutole, plus rimsulfuron. It provides early-season, residual control of grass and broadleaf weeds.

Prequel also controls small, emerged weeds, up to 3 inches tall, in no-till. Adding atrazine, glyphosate or 2,4-D improves preplant burndown results.

Flexstar GT. Syngenta offers a premix of Flexstar plus glyphosate for postemergence use in Roundup Ready soybeans. The active ingredient in Flexstar is fomesafen. Maximum rates vary. Read labels carefully. Spray at 15 to 20 gallons per acre with flat fan nozzles. Add crop oil concentrate, MSO or AMS for glyphosate-resistant weeds.

Tough to solve: volunteer corn growing in continuous corn

When is corn a weed? When it’s volunteer corn growing in corn or soybeans, it’s a weed. And if volunteer corn contains resistant genes to both glyphosate (Roundup) and glufosinate (Ignite), there’s no effective way to take it out of continuous corn.

That’s the conclusion reached by Tom Bauman and Bill Johnson, Purdue University weed control specialists. There are still several options for taking glyphosate- and glufosinate-resistant volunteer corn out of soybeans.

Johnson began a study last year at the Purdue Agronomic Research Center near West Lafayette that actually looked at options for removing remaining stands of herbicide-tolerant corn in replant situations. It shed light on the volunteer corn dilemma as well.

If you went by their first year of research, where corn was planted very late due to weather delays, you would leave volunteer corn anyway, Johnson says with a grin. Those plots actually yielded better than plots without volunteer corn. No one expects all years to be like 2009.

“They thinned back from F1 seed,” Bauman notes. “In volunteer corn situations, you’re usually dealing with F2 seed. Ears wouldn’t normally be as big.”

The meat of the 2009 study looked at how to best handle herbicide-resistant corn in replant situations, Johnson notes. For example, if you’re down to 8,000 plants, should you leave it or kill it before replanting?

If it carries only the glyphosate gene or only the glufosinate gene, you could take it out with the respective product — Roundup on glufosinate-tolerant corn, and Ignite on glyphosate-tolerant corn. But if it has tolerance to both, Johnson says choices are more limited. He’ll continue pursuing answers.

Meanwhile, expect more, not less, of these perplexing quandaries as more herbicide-resistant traits come onto the market.

Variety of generic herbicides set to hit market this spring

You may see a variety of new herbicide product names this spring. But you may not be looking at new chemistry. Many new names are look-alike herbicides with the same active ingredients as those already on the market.

“Once patents run out, other companies can make the product,” explains Tom Jordan, Purdue University weed control specialist. Patents are typically 17 years. But the patent clock starts when the company receives a patent. In many cases, that’s several years before the herbicide hits the market.

Here’s a rundown of new names you may see, and the product that they’re equivalent to in terms of active ingredient. Make your own comparisons on price, and read labels to compare formulations. Determine who services the generic herbicide should problems arise.

Cloak DF from Nufarm is the same as Canopy EF.

Cloak EX is the same as Canopy EX.

Tricor DF is the same as Sencor.

Halomax is generic for Permit.

Sandea is also generic for Permit.

Encompass is the same as Valor.

Dawn contains the same active ingredient as Reflex.

Rhythm is the same as Flexstar.

Parazone is the same as Gramoxone.

Vida from Gowan is equivalent to ET and Aim.

Sometimes companies later patent a different formulation of their original product. Then the patent clock for that formulation begins again, Jordan explains. Check labels carefully when you’re unfamiliar with names to see exactly what you’re getting for your money.

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PERPLEXING PUZZLE: How do you remove herbicide-tolerant volunteer corn in continuous corn? Bill Johnson wants to find out.

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LOOK AND COMPARE: Dave Smith likes to visit weed trials to see results firsthand. He’s the Extension ag educator in Johnson County.

This article published in the February, 2010 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.