Enlist Stewardship

Follow Federal and State Rules for New 2,4-D Trait System

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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Protecting susceptible crops, like the tomatoes to the left, from Enlist Duo applications to Enlist crops (on the right) this year will require vigilance from applicators. (Photo courtesy of Dow AgroSciences)

ROCKVILLE, Md. (DTN) -- Applicators will be heading into cotton fields with a new 2,4-D herbicide this year, and avoiding off-target damage will be key for the future of this weed control system.

Dow AgroSciences' Enlist Weed Control System consists of Enlist Duo, a glyphosate-2,4-D premix and Enlist cotton, corn and soybeans designed to be tolerant of both glyphosate and 2,4-D. (Enlist soybeans and cotton are also tolerant of glufosinate.) For this year, only the cotton trait is fully commercialized and available under Dow's PhytoGen cottonseed brand.

It's important to understand that some label restrictions for Enlist Duo differ from the competing dicamba technology from Monsanto, known as Roundup Ready 2 Xtend. A web of state restrictions is also in place that can exceed the federal label for Enlist Duo.

Don't feel alone if the details of the new herbicide trait system have your head spinning this spring. Never have herbicide labels come to the sprayer with this many requirements -- from both an application and an herbicide resistance management standpoint.


Jonathan Siebert, Dow AgroSciences' Enlist field sales leader, said the company has "corn and soybean seed in the bag, ready to go," if key import approvals for the trait come in time for the 2017 growing season (China for corn, the EU and China for soybeans). However, at this late date, introductions are expected to be limited, and most commercial in-crop applications will likely take place in cotton country.

Enlist Duo is designed for burndown, preemerge and in-crop use on Enlist corn, cotton and soybeans. Enlist Duo may also be used as a burndown outside of the Enlist crop system as long as plantback restrictions are observed.

Mississippi State University scientists have a stern message for Enlist growers: Don't try to save money by using generic 2,4-D formulations in this trait system. In a training module designed by MSU weed scientist Jason Bond, cotton agronomist Darrin Dodds, soybean agronomist Trent Irby and weed scientist Dan Reynolds, the group broke down the dangers of going off-label.

Not only is using another formulation of 2,4-D illegal, but it also increases the risk of off-target movement. The new choline salt of the Enlist Duo herbicide is 88% less volatile than current 2,4-D amine formulations, and it also contains Colex-D technology, a drift retardant that reduces the amount of driftable fine droplets, Siebert noted.

Many 2,4-D formulations on the market are manufactured in plants that also manufacture other herbicides, such as dicamba. Because these herbicides are not designed or labeled for in-crop use on biotech crops, they are permitted to have certain levels of contamination from other herbicides, the MSU scientists said.

"What this means for the growers is that non-approved formulations of 2,4-D may contain trace concentrations of dicamba in concentrations that are great enough to result in severe crop injury and yield loss if used in Enlist crops," the scientists said in the training module. "The bottom line is that trying to save a buck by using unapproved formulations could result in fines or yield losses, thus ultimately costing you much more than you could potentially save."


Enlist Duo is available as a burndown option in 2017. However, if the field is intended for non-Enlist corn or soybeans, growers will face plantback restrictions (seven days for corn and 30 days for soybeans), Siebert noted. There are no plantback restrictions for Enlist Duo burndown applications before Enlist crops. However, University of Illinois weed scientist Aaron Hager advises farmers wait a few days following burndown applications before injuring weeds with the planting operation.

Burndown applicators, as well as in-season applicators, must still follow all Enlist Duo label requirements, Siebert added. Those include restrictions on wind speed, temperature inversions, tank mixes, buffer requirements and tank cleanout.

The label permits spraying Enlist Duo between 0 to 15 mph. However, 3 to 10 mph is the "optimum" window, Siebert said. When wind speeds dip below 3 mph, the chance of a temperature inversion is very high, according to new research from the University of Missouri.

The Enlist Duo label warns against spraying during a temperature inversion. Temperature inversions occur when cold, stable air gets trapped near the surface and spray droplets cannot fall to the ground, and instead hang suspended in the air until the inversion ends and they can be moved off target. The University of Missouri research has shown that the chances of a temperature inversion developing are much higher during the evening hours of clear, windless days. Watching for lateral-moving smoke or dust can also cue applicators into the likelihood of an inversion underway.

Applicators must leave a 30-foot downwind, in-field buffer between Enlist crops and "any area," according to the label. Roads, buildings, prepared agricultural fields and crops that are not susceptible to Enlist can count as part of that buffer. The label forbids spraying when the wind is blowing (at any speed) toward "susceptible crops," namely, commercially grown tomatoes and fruiting vegetables (EPA Crop Group 8), cucurbits (EPA Crop Group 9), grapes and non-Enlist cotton fields.

Tank mixing will be tightly controlled for Enlist Duo. Growers can only use the products listed on this website (http://www.enlist.com/…), which contains a mix of adjuvants and additives for now. Siebert said Dow hopes to have some active ingredients added to the list in time for the growing season, so applicators should continue to check the website through the spring and summer.

Finally, growers face a triple rinse requirement after using Enlist Duo -- first with water, then water plus an optional cleaning agent and then water again. The only exception is for applicators headed for a glyphosate-tolerant cornfield following their Enlist Duo application. In that case, only a single rinse is necessary, the label states.

Applicators should brace for the added time and effort this requirement will take, Siebert said. After thoroughly draining the sprayer system, the first rinse requires filling 10% of the tank with water and circulating it for 15 minutes, as does the third and final water rinse. The second rinse with optional cleaning agents requires a 15- to 20-minute circulation, and the label recommends letting it sit for several hours and preferably overnight.

"This is probably a change from what people have been doing previously in the Roundup Ready world," Siebert noted. "So to go back to using selective chemistry, the one thing we're hammering home is sprayer hygiene and tank cleanout."


Ready to roll? Not quite yet. A number of states have placed additional restrictions on applications of Enlist Duo, via 24(c) labels and other measures. Remember that applicators must comply with whichever rules (federal or state) are most restrictive. Even if you don't see your state below, it would be best to contact your state department of agriculture or Extension service to find out if there are any additional state restrictions before spraying Enlist Duo:

-- South Dakota 24(c): This label presents its own (more restrictive) list of tank mix options. It also forbids spraying if rain is expected within 24 hours and reiterates the limit of two post-emergence sprays per season. See it here: http://bit.ly/…

-- North Carolina 24(c): This label bans spraying when winds exceed 10 mph. It also expands the definition of "susceptible crops" to include more plants. It also requires all in-crop applicators to take a training course from the North Carolina Department of Agriculture and Consumer Services. See it here: http://www.cdms.net/…

-- Louisiana 24(c): This label requires in-crop applicators to take a specific training course from the Louisiana Department of Agriculture and Forestry. See it here: http://www.cdms.net/…

-- Alabama 24(c): This label bans spraying when winds exceed 10 mph, and expands the definition of "susceptible crops" to include more plants. It also requires in-crop applicators to take a training course from the Alabama Department of Agriculture and Industries. See it here: http://www.cdms.net/…

-- Georgia 24(c): This label requires in-crop applicators to take a training course from the Georgia Department of Agriculture. See it here: http://www.cdms.net/…

-- Mississippi is also requiring applicators to complete an online training course on auxin-containing herbicides from Mississippi State University. You can find it here: www.auxintraining.com

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

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Emily Unglesbee