Enlist and Xtend: What Buffers are Mandatory?

Key Points to Remember:

1. A physical buffer of 30 feet must be included between a field treated with Enlist Duo and a downwind sensitive area.
2. Xtendimax, Engenia, and FeXapan require a 110-foot physical buffer between treated fields and downwind sensitive areas.
3. Labeling for Enlist Duo, Xtendimax, Engenia, and FeXapan forbid application if wind is blowing toward sensitive species or plant groups listed for each herbicide.
4. Cotton is highly sensitive to 2,4-D; soybean and peanut are highly sensitive to dicamba; fruiting vegetables, many flowering trees, ornamentals are highly sensitive to 2,4-D and dicamba.

Enlist Duo is the only herbicide product that contains 2,4-D labeled for application to crops in the Enlist Weed Control System. Xtendimax with VaporGrip, Engenia, and FeXapan plus VaporGrip are the dicamba herbicide products labeled for use in Mississippi for application to crops in the Roundup Ready Xtend Crop System. Labeling for these herbicides detail requirements that either restrict application or require buffers between the treated field and sensitive areas or susceptible crops. Sensitive areas and susceptible crops are not the same when considering applications of these new auxin herbicide products.

An actual physical buffer is required when a herbicide application is made to a field with a sensitive area in proximity downwind. A physical buffer of 30 feet must be included between a field treated with Enlist Duo and a downwind sensitive area. Xtendimax, Engenia, and FeXapan require a 110-foot physical buffer between treated fields and downwind sensitive areas. The critical point is that these are downwind buffers. If the wind is blowing toward a sensitive area during application, the buffer is required. No buffer is needed if wind is blowing away from a sensitive area during the application.

While the requirement for a physical downwind buffer between a herbicide-treated field and a sensitive area is a new concept, the sensitive area designation is represented on older herbicide labels. For example, the spray drift management sections of the labels for Liberty 280 and Flexstar GT both address sensitive areas using identical language. These labels state, “the pesticide should only be applied when the potential for drift to adjacent sensitive areas (e.g. residential areas, bodies of water, known habitats for threatened or endangered species, non-target crops) is minimal (e.g. when wind is blowing away from the sensitive area)”. The labels for new auxin herbicide simply take these requirements a step further by requiring the physical downwind buffer to sensitive areas.

For the four new auxin herbicide products labeled in Mississippi, the definition of a sensitive area would be similar to that for Liberty 280 and Flexstar GT described above. Any residential areas, bodies of water, or known habitats for threatened or endangered species should be considered a sensitive area and would require the designated physical downwind buffer.

Labeling for Enlist Duo, Xtendimax, Engenia, and FeXapan contain similar language regarding areas that may be included in the physical downwind buffer between treated fields and sensitive areas. This language is paraphrased below;

1. Roads, paved, or gravel surfaces
2. Agricultural fields prepared for planting
3. Planted agricultural fields
   1. Enlist Duo label: “Planted agricultural fields (Except those listed in the ‘Susceptible Plants’ section).”
   2. Xtendimax and FeXapan: “Planted agricultural fields containing: corn, dicamba tolerant cotton, dicamba tolerant soybean, sorghum, proso millet, small grains, and sugarcane.”
   3. Engenia: “Planted agricultural fields containing asparagus, corn, dicamba tolerant cotton, dicamba tolerant soybean, sorghum, proso millet, small grains, and sugarcane.”
4. Areas covered by the footprint of a building, shade house, silo, feed crib, or other man made structure with walls and/or a roof.

In addition to sensitive areas, labels for new auxin herbicide products also address susceptible crops and plants. Unfortunately, susceptible crops and plants are handled differently depending on herbicide product. Information for these is summarized for each herbicide below:

1. Enlist Duo: “At the time of your application, the wind cannot be blowing toward adjacent commercially grown tomatoes and other fruiting vegetables (U.S. EPA Crop Group 8), cucurbits (EPA Crop Group 9), grapes, or cotton without the Enlist trait.”
2. Xtendimax/FeXapan: “DO NOT APPLY this product when the wind is blowing toward adjacent commercially grown dicamba sensitive crops, including but not limited to, commercially grown tomatoes and other fruiting vegetables (U.S. EPA Crop Group 8), cucurbits (EPA Crop Group 9), and grapes.”
3. Engenia: “DO NOT APPLY when wind is in the direction of neighboring specialty crops. Specialty crops include, but are not limited to, tomatoes and other fruiting vegetables (U.S. EPA Crop Group 8), cucurbits (EPA Crop Group 9), peas, potato, tobacco, flowers, fruit trees, grapes, ornamentals, including greenhouse and shade house grown broadleaf plants.”

The regulations regarding susceptible crops and plants appear simple. If the wind is blowing toward one of the species or plant groups listed above, do not make the herbicide application. Unfortunately, the guidelines are actually not that simple regarding the three dicamba herbicide products. For example, compared with labeling for Xtendimax and FeXapan, the Engenia label contains a more detailed list of species and plant groups that restrict applications. Additionally, the labels for all three dicamba herbicide products include the phrase “but not limited to” when listing restrictive species and plant groups. However, none of the labels offer an explanation for what additional species and plant groups would be included in “but not limited to.”

What does all this label jargon mean? How can a grower/applicator distill this information and determine specifically what they need to do when the time arrives to make an application? First, labeling for Xtendimax, Engenia, and FeXapan all explicitly state that avoiding spray drift is the responsibility of the applicator. Obviously, this applies for Enlist Duo as well. Second, it is important to remember that cotton is highly sensitive to 2,4-D while soybean and peanut are highly sensitive to dicamba. Fruiting vegetables and many flowering trees, shrubs, and ornamentals are highly sensitive to both 2,4-D and dicamba. Third, if a grower/applicator knows the core of the information presented here, observes other specifications for application of the herbicide of choice, is aware of what plants are in proximity of the field to be treated, and applies common sense, then the potential for problems during the application should be minimized.

More information for each of these herbicide products can be found at the following sites:

Enlist Duo: www.enlisttankmix.com

Xtendimax with VaporGrip: www.xtendimaxapplicationrequirements.com

Engenia: www.engeniatankmix.com

FeXapan plus VaporGrip: www.fexapanapplicationrequirements.dupont.com

Producers interested in purchasing auxin-containing herbicides intended for in-crop use on 2,4-D- or dicamba-tolerant crops must first complete mandatory online training. The self-paced online training may be accessed 24/7 at http://www.auxintraining.com via most devices, including tablets and personal computers. In Mississippi, additional conditions placed on the use of these auxin herbicides prohibit producers from applying herbicides in wind speeds in excess of 10 miles per hour. Applicators are required to keep application records. Licensed pesticide dealers are required to keep records pertaining to the sales of these herbicides.