Enlist Corn, Cotton, Soybeans: 6 Points You Need to Know – DTN

Enlist crop acreage is set to expand significantly in 2020, thanks to a boost from new volumes of Enlist E3 soybeans on the landscape.

Corteva Agriscience, which owns the technology, announced in a January press release that it expects E3 soybeans alone to reach 20% of the U.S. soybean market share this year.

That means many U.S. growers will be using the technology for the first time and could face a learning curve, weed scientists told DTN. Enlist corn, cotton and soybeans can be sprayed with glyphosate, glufosinate and two 2,4-D-choline products marketed by Corteva, Enlist One and Enlist Duo.

Here are the top 6 things to keep in mind when spraying Enlist herbicides this year.

1. Federal Label Restrictions

Enlist One and Enlist Duo herbicides come with some federal label restrictions that applicators should keep in mind. You can find the labels here: http://www.cdms.net/… and here: http://www.cdms.net/…, but here are some key rules to remember:

–No aerial applications permitted

–Applicators must choose from a chart of pre-approved, low-drift nozzles

–Applicators should consult a sensitive crop registry before application

–Do not apply when winds surpass 15 mph

–Do not apply during a temperature inversion

–Maintain a 30-foot downwind buffer at all times

–Do not apply when the wind is blowing toward a sensitive crop, such as fruiting vegetables, grapes and non-Enlist cotton fields.

That last requirement is key, said Scott Nolte, weed scientist with Texas A&M AgriLife Extension. Off-target 2,4-D movement and injury has been a significant issue in cotton-growing regions, given how sensitive non-Enlist cotton is to 2,4-D, he noted.

And while cotton acreage isn’t widespread in the Midwest, many specialty crops such as grapes, tomatoes, and trees are just as susceptible to 2,4-D injury as they are to dicamba, he noted.

“What we’ve tried to beat hard on here is that the 30-foot buffer cannot protect susceptible crops,” he said. “If the wind is blowing toward a sensitive crop, you just do not spray,” he said.

2. State-Specific Restrictions Do Exist

Given the sensitivity of non-Enlist cotton to 2,4-D, a number of cotton-growing states have issued Section 24(c) special local needs labels further restricting the use of Enlist herbicides. These include:

–ALABAMA: No spraying at wind speeds above 10 mph and applicators must attend annual auxin-specific training

–ARIZONA: Applications banned in certain counties

–GEORGIA: State-specific annual training required before application

–NORTH CAROLINA: No spraying at wind speeds above 10 mph and applicators must attend annual auxin-specific training

This is not necessarily a comprehensive list, and some states, such as Texas, have issued training requirements for auxin herbicides outside 24(c) labels. All applicators should be sure to check with their local state departments of agriculture for any additional uses or restrictions on Enlist herbicides.

3. Enlist Herbicides: What’s the Difference?

Corteva offers two 2,4-D-choline products to use over-the-top of Enlist crops this year: Enlist One and Enlist Duo. Here are some key differences:

–ENLIST ONE: Enlist One contains a single active ingredient: 2,4-D choline. This herbicide is the more flexible of the two, simply because it has a larger list of legal tank mix options for herbicides, insecticides, fungicides, AMS products, plant growth regulators and other products. See the list here: https://www.enlist.com/….

–ENLIST DUO: Enlist Duo is a 2,4-D-choline and glyphosate pre-mix. As such, it comes with a smaller list of legal tank mix ingredients than Enlist One. See the list here: https://www.enlist.com/…. Note that one particularly popular tank mix option — glufosinate — is not currently legal for use with Enlist Duo.

4. How to Avoid Tank Mix Trouble with Glyphosate and AMS 

Not all glyphosate herbicides are made the same, and for Enlist tank mixes, that matters. Specifically, potassium-salt (or K-salt) glyphosate formulations, such as Roundup PowerMAX, appear to have some physical incompatability with the Enlist One herbicide, said North Dakota State University Extension weed scientist Joe Ikley.

“If a K-salt of glyphosate and Enlist One come into contact with each other — either by adding them to a tank mix quickly or having them touch either in the absence of water — we had salting-out issues,” Ikley explained. During jar tests, a heavy white residue developed, the result of individual crystals forming, Ikley said.

The messy mix created a sludge that could plug up filters and compromise the efficacy of the tank mix, Ikley said. Once the salting out had occurred, no amount of mixing could get the crystalized matter back into solution, he added.

Glyphosate formulations with a DMA-salt (such as Durango DMA) or an IPA-salt (such as Abundant Extra) did not show any such tank mixing issues, Ikley said.

A similar issue appeared when AMS was added to the tank mix immediately before adding Enlist One, Ikley reported. The same “chalky white mess” emerged as the choline salted out. “We tested three different approved AMS products and had the same issue,” he said.

Fortunately, the solution is simple, if a bit time consuming. Corteva has released official tank mix procedures noting that applicators should add tank mix ingredients — particularly K-salt of glyphosate and glufosinate ammonium products — one a time, pausing to allow recirculation between additions.

“We’re recommending that, for dry ingredients, you give it five minutes to mix, and for liquid, you give it two minutes,” Ikley said. That can seem like a long time in the rush of spring and summer spray season, but it will save applicators a much more time-consuming mess in their tanks, he added.

See the Corteva guidelines here: https://www.enlist.com/…. See Ikley’s presentation on Enlist tank mixing issues for the industry group Take Action here: https://iwilltakeaction.com/….

5. Glufosinate and Enlist Tank Mixes: Know the Rules 

Part of the appeal of Enlist crops is the ability to spray both glufosinate and 2,4-D-choline postemergence. However, applicators need to be aware that it is not legal to tank mix glufosinate with Enlist Duo, Ikley stressed.

Moreover, tank mixing glufosinate and Enlist One, which is legal, requires some adjustments, due to conflicting label restrictions.

“They require different spray parameters to optimize efficacy,” Ikely explained. “If you use Enlist One, you are tied to the approved low-drift nozzles on the label, which are not ideal for Liberty [glufosinate].”

Increasing your carrier volume can help the situation by producing better spray coverage, he said. Enlist One alone calls for a spray carrier volume of 10 to 15 gallons per acre; glufosinate herbicides generally require 15 to 20 gallons per acre. Ikley recommends growers use at least 15 gallons per acre for an Enlist One-glufosinate tank mix.

And remember, regardless of what other herbicides may be in your Enlist tank mix, applicators must follow the restrictions on the Enlist labels, such as buffers and wind speed requirements.

6. Herbicide Antagonism Could be a Problem

Although the exact mechanism isn’t clear, auxin herbicides such as dicamba or 2,4-D are known to inhibit the activity of Group 1 herbicides such as clethodim (Select).

That could complicate the popular practice of adding Group 1 herbicides to the tank to control volunteer corn in soybean fields, cautioned Bill Johnson, Purdue University Extension weed scientist. He estimates that this occurs on more than 50% of Indiana soybean acres each year.

Scientists have also documented auxin herbicides such as dicamba antagonizing glyphosate in tank mixes, and growers should be aware of this possibility with Enlist herbicides, too, Johnson added.

For Group 1 herbicides, the standard first step in combating this problem is to increase the rate anywhere from 25% to 50%, Johnson said. Another effective, but less appealing, measure would be to make separate trips across the field with Enlist and Group 1 herbicides, with several days in between each, he added.

Adjuvants with crop oil in them, which are permitted for Enlist One tank mixes, can also help increase the efficacy of the Group 1 herbicides in the tank, Johnson said.

For more, see a Take Action webinar Johnson led on the topic of herbicide antagonism here: https://iwilltakeaction.com/….

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com.

Follow her on Twitter @Emily_Unglesbee.