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8 Ways to Make New Herbicide-Tolerant Traits Work

Rotating different herbicide modes of action and applying pre-emergence residual herbicides in Jim Call’s corn and soybeans are a couple ways the Madison, Minnesota, farmer fends off herbicide-resistant weeds.

These days, though, keeping ahead of glyphosate-resistant weeds like waterhemp keeps Call busy. “I’ve been dealing with it for at least three years,” he says.

Still, something’s missing. “Newer technology would help open up new weed-control avenues that I could use,” says Call.

It’s coming. Three new herbicide-tolerant technologies – one that will be on tap in 2015 on a limited basis and a couple others soon likely to follow – will be available for farmers to use. Here’s a preview.

• Dow AgroSciences

Federal regulators have approved the Enlist Weed Control System from Dow AgroSciences. The system includes tolerance to 2,4-D and glyphosate in corn and soybeans, and fop herbicides in corn.

The herbicide’s new 2,4-D formulation, 2,4-D choline, has less potential for off-target movement than current formulations, say Dow officials. The new formulation will be included with glyphosate in the system’s herbicide component, Enlist Duo. Dow plans to market the system to select growers in 2015.

Federal regulators initially approved the system in Illinois, Indiana, Iowa, Ohio, South Dakota, and Wisconsin. Regulators are also considering granting registration in Arkansas, Kansas, Louisiana, Minnesota, Mississippi, Missouri, Nebraska, North Dakota, Oklahoma, and Tennessee.

Dow has also collaborated with MS Technologies, a West Point, Iowa, firm, to develop Enlist E3 soybeans. These soybeans will tolerate 2,4-D choline, glyphosate, and glufosinate. Federal approval was also granted to these soybeans.

• Monsanto

Waiting in the wings is Monsanto’s Roundup Ready 2 Xtend System. The system’s Genuity Roundup Ready 2 Xtend soybeans will tolerate glyphosate and new formulations of dicamba.

Monsanto’s herbicides for this system will include Roundup Xtend, a glyphosate-dicamba premix. Roundup XtendiMax is a stand-alone formulation. Monsanto officials say these dicamba components contain proprietary VaporGrip technology that reduces dicamba volatility when compared with existing dicamba formulations.

BASF’s Engenia herbicide is another new low-volatility dicamba herbicide that can be used in the system, say BASF officials.

Federal regulators have not yet approved the system.  However, approval is expected later this year. Pending regulatory approval, a commercial launch for soybeans is planned for 2016, says John Combest, a Monsanto spokesperson.

• Bayer CropScience and MS Technologies

The Balance Bean GT Soybean Performance System from Bayer CropScience and MS Technologies will be paired with a glyphosate and isoxaflutole-based herbicide with the HPPD inhibitor mode of action. Isoxaflutole is the active ingredient in Balance Flexx herbicide, currently used on corn. The system’s herbicide will be called Balance Bean.

The system is not yet approved, but the firms expect federal approval mid-decade. Bayer and Syngenta are also working on soybean tolerance to isoxaflutole and mesotrione, another HPPD-inhibitor herbicide contained in the corn herbicide, Callisto. Bayer and Syngenta officials say approval is expected toward the end of this decade.

Change Your Plan

When applied according to label directions, all new products give excellent weed control.

Still, you’ll need to think differently about weed management from now on. Consider the following factors.

1) Don’t lock into one system. Remember when your mom or dad used to nag you about doing your homework? Call’s agronomist played that role in the heady early days of the Roundup Ready system, when just two postemergence passes of glyphosate were needed in corn and soybeans.

“Our agronomist complained about the Roundup monoculture for years, saying, ‘It will come back to bite you guys,’” says Call.

It did. Soon, glyphosate-resistant weeds infested the Corn Belt.

Resistance isn’t just limited to glyphosate, either. Even though the traits and formulations are new in new herbicide-tolerant systems, the herbicides aren’t. Waterhemp – the scourge of Corn Belt soybeans – already has biotypes that resist herbicides from six modes of action including synthetic auxins (2,4-D) and HPPD inhibitors (tembotrione, as in Laudis).

The herbicides themselves didn’t spur resistance, but repeated use by farmers over time did.

“I don’t think the new technologies will be the cure-all for weed resistance,” says Call. “We became overconfident with Roundup (Ready) and overused Roundup. With the new technologies and new chemicals, we will have to watch that again.”

Now, he plans to mix up multiple herbicide modes of action and application times to keep weeds off balance.

2) Treat earlier. Ever heard a fisherman telling an arm-extending “that fish was this big” whopper? It’s akin to a farmer bragging about spraying and killing 18-inch high waterhemp.

Waiting to spray weeds that tall in one postemergence shot may have worked in the days of Roundup Ready. It won’t with these new technologies. Labels for these products will likely zero in on postemergence applications when weed height is 4 inches or less.

“Start thinking of spraying when waterhemp is at the 2-inch height,” says Craig Lamoureux, a Monsanto technical development representative. “By the time you get the sprayer ready, it could grow to a 4-inch height on that same day.”

Use a preemergence residual herbicide. This adds multiple modes of action and helps reduce pressure on old and new postemergence herbicide-tolerant technologies. It doesn’t eliminate resistance potential, though, as any herbicide selects for resistance, says Aaron Hager, University of Illinois Extension weed specialist.

“We control waterhemp using preemergence chemicals and again early in when it’s a couple inches tall (with postemergence herbicides),” says Call. “We are nuts about controlling it when it is small. You can control anything if you have a thick enough wallet. But with low-price (crops) situations, you just can’t spray $50 to $70 per acre worth of herbicides.”

Cultural ways to nix weeds early include 15-inch rows. “Early canopy closure is a good weed control tool,” says Lamoureaux.

Cover crops can also smother early emerging weeds. “The most vulnerable stage (for waterhemp) is the seed stage,” says Hager.

3) Change your neighboring field assumptions. Charlie Johnson, who farms with his brother, Allan, near Madison, South Dakota, has had portions of their farm’s organic fields damaged by glyphosate and Banvel (dicamba) drift for the last four years.

That makes Johnson particularly leery of the new herbicide-tolerant technology.  “There’s an assumption now that everyone has Roundup technology in their fields,” he says. “In the past 10 years, there’s been a tendency among applicators that ‘you take some of my drift, you take some of mine.’ They forget how sensitive non-GMO soybeans are to drift.”

4) Revamp your nozzles. Dicamba and 2,4-D have historically been prone to off-target movement via drift and/or volatilization. However, the firms manufacturing herbicides for the 2,4-D-tolerant and dicamba-tolerant systems say they have made good strides in reducing off-target movement potential.

Dow officials say the Enlist Duo herbicide that contains 2,4-D choline has 87% and 96% reduction in volatility compared to existing 2,4-D amine and 2,4-D ester formulations, respectively. Meanwhile, Enlist Duo cuts drift potential 90% compared to older 2,4-D formulations when applied with low-drift potential nozzles, say Dow officials.

That’s also the case with new dicamba-tolerant technology, say BASF and Monsanto officials. Both firms say their dicamba-tolerant forms are low in volatility.

Flat-fan nozzles won’t cut it for these systems. A number of low-drift nozzles will be offered to give farmers and applicators choice, say Dow officials. Monsanto and BASF will also recommend low-drift nozzles on product labels.

Follow label directions and use only approved formulations of these chemistires. This not only ensures optimal application but also reduces off-target liability.

“If you go off-label with flat fans, you are 100% liable for that misapplication,” says John Cantwell, Monsanto technical development representative.

5) Mimic Mr. Clean with your sprayer. Besides using special low-drift nozzles stated on the label, you’ll need to clean out your spray tank and lines to avoid spray contamination between different chemistry types.

“We recommend a triple rinse,” says Combest.

Budget time to do it. “Cleanout will be more difficult on big sprayers,” says Call. “There can be a lot of spray in those 120-foot booms.”

Without a doubt, it will be a challenge, adds Hager. “Applicators will have to allow for a thorough cleanout process. It doesn’t take that much dicamba to cause injury symptoms.”

6) Monitor boom height and speed. In the case of BASF’s new dicamba formulation Engenia, boom height no more than 24 inches above the canopy is recommended.

“Slow down,” says Mark Storr, BASF technical development representative. When speed increases, booms can bounce above that 24-inch threshold.

7) Watch the wind. Storr says it’s best to spray when wind speed is between 3 and 15 mph. Spraying in still conditions is not recommended, as temperature inversions can move spray off target. Above 15 mph, wind can carry the chemical off target.

Consider wind direction, too. If it’s blowing toward a vineyard, don’t spray. “You can use wind direction to your advantage, if it’s blowing away from a sensitive crop, “ Storr says.

Expect setbacks. “The distances will be defined by rate and wind speed,” he says.

8) Have sufficient spray carrier volume. This ensures enough water to produce large enough droplets to help reduce off-target movement potential.

In Engenia’s case, 10 gallons per acre is the minimum. This helps ensure good coverage and produces large droplets not prone to drift, says Storr.

Many are watchingEPA approval of the Enlist Duo herbicide includes first-time-ever pesticide drift restrictions that include:

• A 30-foot in-field no-spray buffer zone around the application area.

• No pesticide application when the wind speed is over 15 mph.

• Only ground applications.

Requirements also include extensive surveying and reporting to EPA, grower education, and remediation plans. This doesn’t apply only to Enlist. Officials for the EPA intend to apply this approach for all existing and new herbicides used on herbicide-tolerant crops.

The upshot is, this technology will diversify weed management and help forestall herbicide-resistant weeds.

That said, herbicide-tolerant systems will also be closely scrutinized for off-target movement. After wrestling with four consecutive years of drift, Johnson is skeptical.

“It’s like the basics of cattle farming, in that you don’t let your cows go on the other side of the fence,” he says. “It’s the same way with herbicides. You don’t want them to jump the fence.”

(Source – http://www.agriculture.com/crops/pesticides/herbicides/8-ways-to-make-new-herbicidetolert_179-ar46691)

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