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Enlist Soybean Varieties--The Latest Tool for Managing Herbicide-Resistant Weeds

Enlist E3 (E3) soybean varieties (enlist.com–contains information on all components of the Enlist system) contain traits for resistance to 2,4-D (auxin herbicide), glyphosate, and glufosinate. Both Enlist Duo (contains both glyphosate [Group 9] and 2,4-D choline [Group 4]) and Enlist One (2,4-D choline-only product) herbicides were developed to be used in this system, and are the only 2,4-D-containing herbicide products labeled for application to Enlist crops. Click here for approved tank mix partners with each of the 2,4-D herbicide products, here for a list of seed companies that have E3 varieties, and here for each seed company’s website.

Both Enlist Duo and Enlist One herbicides (click here to access labels) may be applied to Enlist soybeans anytime after soybean emergence but no later than the R2 or full flowering stage. Both products may be applied as a preplant burndown to fields that will be planted to non-Enlist soybeans. In this case, apply Enlist Duo no less than 30 days prior to planting, and apply Enlist One no less than 7 days (1 pint/acre rate) or 15 days (2 pints/acre rate) prior to planting. Do not apply either product on sandy soils with less than 1% organic matter. Neither product is to be aerially applied, and neither is to be applied within 30 days of harvest. Consult each product’s label for additional application guidelines and restrictions.

Notice that glufosinate (Group 10) is not an approved tank mix partner with Enlist Duo, so they must be applied separately. However, both glyphosate and glufosinate herbicides, either together or separately, can be tank-mixed with Enlist One. Thus, Enlist One appears to offer greater flexibility for a customized postemergence weed control program that incorporates multiple modes of action.

Ratings for expected weed control by the two above Enlist herbicides can be accessed here ( p. 41). As noted in this table, both Enlist Duo (2-4,D + glyphosate) and Enlist One + glufosinate provide excellent expected weed control of most problem weeds that populate Midsouth soybeans. However, Enlist herbicides applied to Enlist soybean varieties must not be relied on alone to manage weeds when herbicide-resistant weeds are present. Using a diversified approach of applying both residual and postemergence herbicides with different modes of action in combination with sound agronomic best management practices will remain the only durable weed management system for soybeans.

In a 2012 article from Purdue University Extension, a section is devoted to “Factors Affecting Off-Site Movement”. Drift and volatility are the two contributing components to off-site movement of auxin herbicides. The segment on drift, which is the physical movement of spray particles by wind away from the target, provides details about the factors that contribute to drift and how these factors can be managed. The segment on volatility, which is the movement of the gaseous form of the herbicide after its deposition on the intended target, provides details about factors that contribute to volatility, and how this process can be lessened or minimized. Click here for a detailed discussion of these topics.

The volatility of the above 2,4-D herbicide products compared to that of dicamba herbicides currently being applied to dicamba-tolerant soybean varieties is not objectively documented, and likely will not be known until there is widespread application of Enlist herbicides to Enlist crops. Anecdotal evidence indicates that the Enlist herbicides are far less likely to volatilize compared to the dicamba herbicides. It is understood by this author that soon-to-be-published results from industry-funded research on this subject are forthcoming.

The United Soybean Board [USB] has produced a list of BMP’s to use when applying auxin herbicides to auxin-tolerant crops. The article titled “Managing 2,4-D and Dicamba in Enlist and Xtend Soybean” is a component resource of USB’s “Take Action Against Herbicide-Resistant Weeds” program. This four-page article contains all current pertinent information that should be considered when using these herbicides (technical editing was provided by Drs. Bish and Bradley of the Univ. of Missouri and Dr. Bill Johnson of Purdue Univ.).

Composed by Larry G. Heatherly, Mar. 2020, larryheatherly@bellsouth.net