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Get to know the new herbicides before you spray

Mississippi State University weed scientist says there's a "disturbing level of confusion" about new herbicide technologies.

You might think Jason Bond was stating the obvious in his presentation at the Delta Ag Expo in Cleveland, Miss. After all, weed scientists have been talking about the Xtend and Enlist traits and herbicides for at least four or five years.

But Dr. Bond, Extension/research professor at Mississippi State University, was emphatic about which herbicides growers should use on which crops when they begin applying them in their crops this spring.

“There is zero cross-resistance between these two weed control systems,” said Dr. Bond, one of four scientists who spoke on the new herbicide technologies and varieties at the Expo. “Enlist Duo will kill Xtend crops and any other non-Enlist crops. Dicamba will kill Enlist crops and any other non-Xtend crops.

“If you don’t remember anything else I say, you’re going to be money ahead if you remember that because I promise you there is a disturbing level of confusion about that out in the world,” he noted.

Growers who plant Enlist cotton in 2017 can spray it with Enlist Duo herbicide (2,4-D choline and glyphosate) and glufosinate. Xtend cotton can safely be sprayed with dicamba, glyphosate and glufosinate, according to labels available for 2017.

Rates and timing

In soybeans, both Enlist soybeans and Enlist E3 soybeans are tolerant to 2,4-D, glyphosate and glufosinate. Crops with the Xtend trait, on the other hand, are resistant to glyphosate and dicamba.

Dr. Bond also discussed rates and timing strategies for the new herbicide formulations in this video from the Delta Ag Expo

In the dicamba-tolerant system, Monsanto’s Xtendimax is a 2.9-pound-per-gallon product while Engenia, BASF’s product, is a 5-pound-per-gallon product “so the volumetric rate for the two is different,” said Dr. Bond.

“If you use Clarity, Banvil or any of the older dicamba products in a burndown timing, more than likely you used 8 ounces to the acre, which is .25 pound,” he noted. “So this rate would be twice what we have historically used in a burndown application. Higher rates are better. That’s a good resistance management strategy.”

The minimum rate for the new formulations is .5 pound per acre, which is 22 ounces of Xtendimax or 12.8 ounces of Engenia. That’s also the maximum rate. For soybeans growers can make two applications or 44 ounces of Xtendimax or 25.6 ounces of Engenia postemergence.

Four applications possible

“The difference with cotton is the label says you can use up to four applications,” he said. “Hopefully, we wouldn’t need to make four applications, but the label reads that it allows up to four. So you can have a total of 88 ounces of Xtendimax for a post application and an annual, which would include your preplant burndown (or up to 51.2 ounces of Engenia in four applications.”

For Enlist Duo, which is a combination of 2,4-D Choline and glyphosate, growers can make two postemergence applications of up to 4.75 pints per acre (one pound each of 2,4-D and glyphosate). Growers can make up to two applications in season for a total of 9.5 pints or three, including a preplant, for 14.25 pints.

“Timing is a little bit different from what we’ve been accustomed to using,” he said.

In soybeans, Xtendimax and Engenia can be applied from emergence to the R-1 stage of plant development. The glyphosate label for Roundup Ready 2 soybeans reads applications can be made from emergence to R-2

“So you’re one growth stage earlier with the dicamba products than you are with the Roundup-only application. The question is how big is an R-2 soybean?” Dr. Bond asked. “Pretty small. It could be real small, depending on a number of factors, including weather, planting date, variety. So keep that in mind that you could be hitting a cut off pretty early in the development of your soybean crop.”

Seven days prior to harvest

In cotton, applications of Xtendimax and Engenia can be made up to seven days prior to harvest. The recommendations for both crops call for controlling weeds before they exceed 4 inches in height.

“You’re not going to kill two-foot-tall pigweed with Xtendimax or Engenia,” said Dr. Bond. “If someone tells you that, they’re giving you information that is not accurate. At 5, 6 or 7 inches, you’ll kill a lot of them, but control is going to start dropping off after 4 inches very rapidly.

“You don’t have any more flexibility with the Xtend system or the Enlist system than you do with the technology we’re currently have at our disposable,” he noted. “That will be another important point to remember.”

On the Enlist Duo system postemergence applications can be made until mid-bloom in cotton. “That’s a little vague there, but, hopefully, we’ve done most of our weed control by the mid-bloom growth stage in cotton.”

In soybeans, postemergence applications of Enlist Duo can be made through the R-2 stage of development “or the same as for glyphosate,” he said. “The weed size is a little less restrictive at 3 to 6 inches. The same concept applies: I’m going to err on the side of 3 to 4 inches instead of 3 to 6 inches.”

Tank mixtures on website

Bond says another change involves what can be mixed with the new herbicide formulations.

“In the past, most labels said you could mix this herbicide with any other herbicide registered for use on that crop,” he said. “That is not the case with Xtendimax, with Engenia or with Enlist Duo.”

With each of these herbicides growers must visit a website before they make an application to “see if what you want to put in the spray tank with that product is legal,” he said. “These are fluid lists; they are going to evolve over time. When I prepared this list in December there were 39 products on the Enlist Duo website. Since then they’ve added 90 additional ones.

“As of today (Jan. 18), the only material you can tank mix with Xtendimax herbicide is water. Nothing else can be mixed with it.”

Those websites are;; and



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