Two new low-volatile formulations of dicamba products designed specifically for use on dicamba tolerant soybeans (Roundup Ready 2 Xtend soybean varieties) and cotton (XtendFlex cotton varieties) have now been approved by the U.S. Environmental Protection Agency. This means that the traits, export approvals, and some herbicides for use on varieties with these traits have finally been approved.
Roundup Ready 2 Xtend (RR2X) soybeans are resistant to both dicamba and glyphosate, while XtendFlex cotton is resistant to dicamba, glyphosate, and glufosinate (Liberty).
Figure 1. RR2X soybean response to dicamba several hours after treatment. Photo by Dallas Peterson, K-State Research and Extension.
The two dicamba products that have been approved for use on Xtend soybeans and cotton are XtendiMax from Monsanto and Engenia from BASF. XtendiMax and Engenia have significantly lower volatility than other dicamba products such as Clarity and Banvel, which are not approved for use on Xtend crops. Use of dicamba products not specifically labeled for use on Xtend crops is an illegal treatment.
Both products have regular labels that are similar to the Clarity label, but use on Xtend crops is addressed in supplemental labels with very specific guidelines for applications to Xtend crops. In addition, there are associated websites which will allow for possible modifications and updates to the supplemental labels over time.
Below are some of the specific guidelines currently listed on the supplemental labels for XtendiMax and Engenia use on Xtend crops.
22 to 44 oz/acre preplant or preemergence with a maximum total of 44 oz
22 oz/acre postemergence with a maximum of two applications
12.8 oz/acre preplant or preemergence with a maximum of two applications
12.8 oz/acre postemergence with a maximum of two applications
Note: 22 oz of XtendiMax and 12.8 oz Engenia both provide 0.5 lb ae dicamba
Application Timing to Xtend Soybeans: Preplant through R1 soybeans
Application Timing to Xtend Cotton: Preplant until 7 days prior to cotton harvest
Application Timing to Weeds: Less than 4 inches tall
Other label requirements
Do not apply with ammonium-containing additives such as ammonium sulfate. These products destabilize dicamba salts and significantly increase volatility.
Do not tank-mix with any pesticide or adjuvant unless that product is listed as an approved tank-mix partner at the associated websites below.
Do not apply with any spray tip other than TTI11004 at the maximum spray pressure specified unless other approved spray tips are listed at the associated websites above.
Apply in a minimum spray volume of 10 gallons per acre.
Do not exceed 15 mph ground speed.
Do not apply during temperature inversions (most likely in the evening hours with calm conditions).
Spray only when wind speed is between 3 and 15 mph.
Do not spray if wind speed is greater than 10 mph in the direction of sensitive areas.
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 (EPA crop group 8), cucurbits (EPA crop group 9), and grapes.
Protection of sensitive areas:
Maintain a 110-foot downwind buffer (when applying 22 oz/acre XtendiMax or 12.8 oz/acre Engenia) or a 220-foot downwind buffer (when applying 44 oz/acre XtendiMax) between the last treated row and the closest downwind edge (in the direction in which the wind is blowing). If any of the following areas listed below are directly adjacent to the treated field, the areas can be considered part of the buffer distance.
• Roads, paved or gravel surfaces,
• Planted agricultural fields containing: corn, dicamba-tolerant cotton, dicamba-tolerant soybean, sorghum, proso millet, small grains and sugarcane. If the applicator intends to include such crops as dicamba-tolerant cotton and/or dicamba-tolerant soybeans in the buffer distance calculation, the applicator must confirm the crops are in fact dicamba tolerant and not conventional cotton and/or soybeans.
• Agricultural fields that have been prepared for planting.
• Areas covered by the footprint of a building, silo, or other man-made structure with walls and or roof
Two additional dicamba products may be improved for use on Xtend crops in the future. DuPont is anticipating a label for FeXapan with Vapor Grip Technology, which will likely be labeled similarly to XtendiMax. Roundup Xtend is a premix of glyphosate plus dicamba with Vapor Grip technology from Monsanto that is also awaiting EPA approval.
General considerations for use of Xtend technology
The Xtend crop technologies and associated herbicides provide a new tool to help manage hard to control weeds, especially glyphosate resistant weeds, but also will require greater stewardship. Spray drift and tank contamination have long been a concern with dicamba herbicides. The new formulations and strict application guidelines are in place to help minimize the potential for off-site movement. Following the label guidelines and using good common sense will be important to help steward the new technologies and avoid potential problems and negative publicity. The illegal applications of non-labeled dicamba products on Xtend crops last summer in the southeast U.S. resulted in major crop damage issues in surrounding fields, and consequently, serious conflicts and lawsuits.
It will also be very important to communicate effectively with neighbors and commercial applicators regarding the presence of susceptible crops and which technologies have been planted in each field.
No new technology should be considered a stand-alone solution to weed management as we have learned with the development of glyphosate resistant weeds. Xtend technology should still be a part of an integrated weed management program that includes good cultural practices and a diversified herbicide program with multiple effective herbicide sites of action, residual herbicides, and timely applications.
Dallas Peterson, Weed Management Specialist
Doug Shoup, Southeast Area Crops and Soils Specialist