Engenia Registered for Dicamba-Tolerant Cotton and Soybean (York)

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BASF received EPA registration for Engenia herbicide, including supplemental labeling for use on DT (dicamba-tolerant) cotton (XtendFlex) and soybean (Roundup Ready 2 Xtend), on December 20, 2016.  This is the second dicamba product recently approved by the EPA for use on DT cotton and soybeans. XtendiMax with VaporGrip Technology, a Monsanto product, was granted supplemental labels for DT cotton and soybean on November 9, 2016. XtendiMax already had a label for typical dicamba uses but was not promoted or sold in North Carolina.

The Engenia supplemental labels for DT crops are, in my opinion, a bit confusing. The supplemental labels at times refer the reader to the full label (referred to as product container label on the supplemental labels). The confusion arises because directions on the product container label sometimes conflict with the directions on the supplemental labels. For example, the product container label allows aerial application whereas the supplemental labels expressly prohibit aerial application. There is also conflicting information concerning application rates, tank mixes, and adjuvant use. Remember, if you are applying Engenia to DT cotton or soybean, follow specific directions on the supplemental labels.

Federal labels for both Engenia and XtendiMax can be found at the websites listed below in Table 1. North Carolina will have SLN (Special Local Need) labels. These SLN labels will have two important requirements that differ from the federal supplemental labels. First, the maximum weed speed at application will be limited to 10 MPH as opposed to 15 MPH on the federal labeling. This is being done in light of the diversity of specialty crops intermingled with cotton and soybean. Second, the SLN labels will require mandatory training. Specifically, the SLN labels will state that “the producer, certified applicator, or person responsible for the application on cotton or soybean, in-crop, must attend Auxin Herbicides – Best Management Practices training that is approved by the North Carolina Department of Agriculture. Dates and locations for the training in cotton areas are in place now but we are still scheduling meetings in non-cotton producing areas. Once all schedules are in place, we will post them.

Table 1 – Websites for Labels

Similar to XtendiMax, the supplemental labels for Engenia on DT cotton and soybean are time-limited. The Engenia supplemental labels expire 2 years from the date of approval, or December 20, 2018. At that time, the EPA can either let the supplemental labels expire or extend the supplemental registrations for an additional three years. That first extension of supplemental labels will depend upon whether or not off-target incidents (drift) are occurring at “unacceptable frequencies”. At the end of the first extension, the EPA will again review the situation. If EPA deems off-target incidents are occurring at “unacceptable frequencies” or if resistance to dicamba is occurring at “unacceptable frequencies”, they can let the supplemental labels expire. To my knowledge, the EPA has not specified what “unacceptable frequencies” are. However, the message from EPA is clear; we must avoid off-target deposition and weed resistance if we expect to have the opportunity to use these products on DT cotton and soybean in the long-term.

Dicamba will be commercially available primarily as three salts although a few products containing dicamba acid are available. The dimethylamine salt (DMA salt) is what is in Banvel and some generic products, and of course Banvel has a reputation for being volatile and causing injury to sensitive non-target crops. The diglycolamine salt (DGA salt), which is in Clarity and some generics, is considerably less volatile than dicamba DMA salt. XtendiMax contains the DGA salt plus VaporGrip, a proprietary ingredient that further reduces volatility. Engenia contains a new salt, the BAPMA salt (N,N-Bis-(3-aminopropyl)methylamine salt) of dicamba. BASF data show a 70% reduction in volatility of the BAPMA salt of dicamba compared with the DGA salt. Monsanto data show that VaporGrip significantly reduces volatility of XtendiMax relative to Clarity. Unfortunately, there appears to be no data directly comparing the drift potential of Engenia and XtendiMax.

Only brands of dicamba specifically registered for use on DT cotton or soybean can be used in-season, or postemergence, on these crops. I suspect no one will claim that Engenia or XtendiMax with VaporGrip Technology are completely non-volatile, but use of these formulations should greatly reduce vapor drift as a cause of off-target sensitive crop injury. In addition to being legal, this is another good reason to use only brands specifically registered for use on DT cotton and soybean.

Discussion below pertains only to Engenia use on DT cotton. See the websites in Table 1 for specifics on DT soybean.

Time of application and rates. Engenia can be applied preplant, at planting, and postemergence to DT cotton at rates listed in Table 2.

Table 2 – Engenia Application Rates and Timing for dicamba-tolerant cotton

Preplant and Preemergence. We have been recommending, and will continue to recommend, dicamba or 2,4-D as a component of burndown programs for no-till or strip-till cotton to aid in the management of glyphosate-resistant horseweed, cutleaf eveningprimrose, wild radish, and other weeds not adequately controlled by glyphosate.  For non-DT cotton, there are waiting periods between application and planting (21 days plus rainfall for dicamba; 30 days for 2,4-D). We can sometimes “cheat” a little on the length of the waiting period, but certainly we can get injury if dicamba or 2,4-D is applied too close to planting. Engenia or XtendiMax, along with DT cotton, will give growers more flexibility in timing burndown applications; there is no waiting period between Engenia or XtendiMax application and DT cotton planting. That said, we will discourage growers from doing their “preplant” burndown and planting on the same day. We need to continue to put our burndown on well in advance of planting. The exception may be where we have a good cover crop and we want to accumulate more biomass before terminating the cover crop.

Cover crops are becoming more widely planted, and often grass/legume mixtures are being promoted by the NRCS. Legumes, such as clover or vetch, can sometimes be difficult to kill. We generally recommend dicamba plus glyphosate to kill legume cover crops. Engenia or XtendiMax and DT cotton will allow us to let the cover crop grow a little longer and still get a good kill. But again, we don’t need to wait until the day we plant to kill that cover.

It should be obvious, but perhaps a point of clarification is in order. Regardless of the brand of dicamba (i.e., even if one is using Engenia or XtendiMax), the current restriction for application at least 21 days before planting plus rainfall still applies on non-DT cotton. And, as we all know, one must follow the label of the specific product being used. Applying a dicamba product not specifically registered for use on DT cotton less than 21 days ahead of planting constitutes a use inconsistent with the label (i.e., illegal use).

Engenia can potentially be applied both preplant and preemergence in no-till DT cotton at 12.8 fl oz per application. I would discourage use in that manner. I think it is preferable to use dicamba in the burndown application to help with glyphosate-resistant horseweed and other weeds hard to kill with glyphosate alone. For various reasons, I would prefer paraquat with the preemergence herbicide for newly emerged weeds.

What about residual control from dicamba? Should we ever consider dicamba preemergence? Dicamba can give short-term (10 to 14 days) residual control of broadleaf weeds. However, it is inconsistent. Interestingly, we see residual activity under conditions opposite of what we see with typical preemergence herbicides. With little to no rainfall, the residual control can be pretty impressive. On the other hand, we see no residual control under rainfall conditions that make other herbicides work. Because of the inconsistency in control and the short period of control, and because we need to keep resistance management in mind, I will discourage routine use of dicamba preemergence.

Postemergence. Engenia can be applied in-crop from DT cotton emergence up to 7 days prior to harvest. The minimum and the maximum rate for a single in-crop postemergence application is 12.8 fl oz. The Engenia rate chart (Table 2) can be a little confusing unless you read it carefully.  The combined total of all postemergence applications cannot exceed 51.2 fl oz, and the combined total of all applications per season (preplant, preemergence, postemergence) cannot exceed 51.2 fl oz. Hence, if Engenia (or any brand of dicamba) is not used preplant or preemergence, then one could potentially make four postemergence applications. For reasons of resistance management and limiting potential for off-target deposition, I would strongly encourage growers to limit their use to two postemergence applications per year. With a good total system (strong preemergence program, timely postemergence with residuals), one Engenia application will often be adequate. And, even though the supplemental label will allow application up to 7 days before harvest, the Engenia should be put in the barn long before that time.

Weed size. The Engenia supplemental label refers the user to the product container label for weed sizes. That label specifies in-crop application to weeds 4 inches or less in height. I have done enough work with dicamba to know that control decreases as weeds become larger. And, I have seen a number of growers who were very disappointed when applying dicamba to knee-high weeds. I am concerned that growers may relegate Engenia (or XtendiMax) to salvage situations. Although we have seen surprisingly good control of larger Palmer amaranth with multiple applications of Liberty plus dicamba, that is a practice we need to avoid. Not only can we lose yield due to competition before beating the weeds down, but such a practice can set us up for resistance evolution.

Tank mixes. The Engenia supplemental labels currently prohibit tank mixing anything (other herbicides, insecticides, adjuvants) with Engenia. The restriction comes because EPA is concerned that mixing another product with Engenia could affect physical properties of the spray solution such that smaller spray droplets (increased drift potential) are formed.

Tank mixes are needed for two reasons. First, a mixture of glyphosate plus dicamba or glufosinate plus dicamba is typically more effective on weeds than dicamba alone. Also, we have become accustomed to applying a residual herbicide such as Dual Magnum, Outlook, or Warrant postemergence to extend residual control further into the season. The second reason we need tank mixes is for resistance management (specifically, avoiding resistance). Tank mixing two or more herbicides having different mechanisms of action but activity on the same species is a well-established resistance management tactic.

The restriction on tank mixes is a serious limitation. Without tank mixes, I would find it hard to recommend Engenia. BASF (Monsanto is in the same situation with XtendiMax) recognizes this limitation and will be conducting the necessary trials to gain EPA approval for specific tank mixtures. Hopefully, some tank mixes will be approved by use season. The EPA is requiring BASF to maintain a website (www.engeniatankmix.com) which lists all the approved tank mixes. The Engenia supplemental labels state that the user must check that website no more than 7 days before applying an Engenia tank mix.

Adjuvants. The above restriction on tank mixes also applies to adjuvants, including drift reduction agents. Before using any adjuvant, one must check with the website mentioned above to ensure that the adjuvant is approved for application with Engenia.

A very important restriction is that no adjuvant containing ammonium salts, such as ammonium sulfate or urea ammonium nitrate, can be used with Engenia. Ammonium salts greatly increase the volatility of dicamba.

Application parameters.  No aerial application of Engenia will be allowed on DT crops. Currently, the Engenia supplemental labels specify use of only TeeJet TTI 11004 nozzles at a pressure not to exceed the manufacturer’s recommended pressure range (15 to 100 PSI; a maximum of 60 PSI is encouraged). Other nozzles that produce extremely coarse to ultra-coarse droplets may ultimately be allowed; if so, approved nozzles will be listed on the website mentioned above. The label requires application in a minimum of 10 GPA, and limits sprayer speed to a maximum of 15 MPH. The label limits boom height to a maximum of 24 inches above the target weed or crop canopy.

Wind speed obviously affects spray drift. The Engenia supplemental labels state that optimum wind speeds are 3 to 10 MPH. The supplemental labels prohibit application when wind speed is less than 3 MPH unless the applicator has taken steps to confirm that a temperature inversion is not present. The federal supplemental labels prohibit application if wind is greater than 15 MPH. However, as mentioned above, the North Carolina SLN labels will limit application to wind speeds not exceeding 10 MPH.

Buffers. The Engenia supplemental labels specify a downwind buffer of 110 feet. Without saying it, this 110-foot buffer is an EPA requirement to protect Threatened and Endangered Species. The following may be included in calculation of the buffer distance: roads, areas covered by the footprint of a manmade structure with walls or roof, agricultural fields prepared for planting, and planted agricultural fields containing DT cotton, DT soybean, corn, sorghum, or small grains. Pastures are apparently not allowed as part of the buffer.  Compliance with this buffer will be relatively easy in large, regularly shaped fields. Small fields and fields that look like a piece of a jigsaw puzzle will be problematic. In many of our fields, compliance with this buffer restriction will be impractical; in such situations, it would be best to not use Engenia.

The Engenia supplemental labels further state that “in addition to the required 110 foot down wind spray buffer, additional protections are required for dicamba sensitive specialty crops.” The supplemental labels do not specify what those additional protections are except that one should not apply when wind is blowing in the direction of neighboring specialty crops. Specialty crops include, but are not limited to, the following: tobacco, grapes, peas, potato, tomatoes, eggplant, okra, peppers, cucumbers, cantaloupe, watermelon, muskmelon, squash, pumpkin, fruit trees, flowers, and ornamentals, including greenhouse and shade house-grown broadleaf plants. The supplemental labels further state that one should not apply “under circumstances where spray drift may occur to food, forage, or other plantings that might be damaged or the crops thereof rendered unfit for sale, use or consumption.” At this point, think about tobacco contracts. The bottom line is that prevention of off-target deposition is the responsibility of the applicator.

Applicators are required to ensure that they are aware of the proximity to sensitive areas, and to avoid potential adverse effects from off-target movement of Engenia.  Before making an application, the applicator must survey the application site for neighboring sensitive areas.  The applicator must also consult sensitive crop registries to locate nearby sensitive areas (if such registries are available). North Carolina now participates in Drift Watch, a sensitive crop registry (https://nc.driftwatch.org/map).

Resistance management. The Engenia supplemental labels have language concerning resistance management. Specifically, they mention diversification in management programs, including multiple herbicides with different mechanisms of action, soil-applied herbicides, full labeled rates, cultural practices, and management of weeds around fields and after crop harvest to reduce seed production. Extension has already been promoting such resistance management practices.

The supplemental labels state that one should scout fields before application to ensure herbicides and rates will be appropriate for the weed species and weed sizes. And, the labels instruct the user to scout fields after application to detect escapes.

Incidences of non-performance (escapes) should be reported to a BASF representative or retailer or reported online at www.non-performance.BASF.US (the website is currently not functional). If resistance is suspected, the weeds should be treated with a non-auxin herbicide or non-chemical methods should be used to remove the escapes and prevent seed production.   

Written By

Dr. Alan YorkNamed Professor Emeritus alan_york@ncsu.eduCrop and Soil Sciences - NC State University
Updated on Jan 3, 2017
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