New Dicamba Products Receive Approval for Use in RR2Xtend Soybean

J.D. Green , Extension Weed Scientist, University of Kentucky

Two dicamba formulations, XtendiMaxTM (Monsanto) and EngeniaTM (BASF), received federal EPA approval in December for use with RoundupReady2Xtend soybean. In addition to federal registration, a pesticide must also be registered and approved within a state before it can be sold. The XtendiMaxTM product received state approval in early January for applications in Kentucky. The EngeniaTM product is still pending state approval, but is anticipated in the near future. These products can be applied before or immediately after planting Roundup Ready 2 Xtend Soybeans or as an in-crop application from emergence (cracking) up to and including the beginning bloom (R1 growth stage of soybeans). The RoundupReady2 Xtend soybean technology provides another tool for targeting weeds that have developed resistance to other herbicide chemistries, but should be combined with other herbicide options and weed management tools for best herbicide resistance management. Because of the chemical characteristics of dicamba, good stewardship by applicators will be required to lessen the potential for off-target movement and damage to sensitive crops and other plants.

Both of these formulations were developed to reduce dicamba volatility losses compared to older dicamba products. Furthermore, there are some unique differences between these two dicamba formulations and relative to other dicamba products.

• XtendiMaxTM with VaporGripTM contains a DGA (diglycolamine) salt of dicamba plus an additive called ‘VaporGrip’ to reduce volatility. The dicamba acid concentration equals 2.9 lb acid equivalent per gallon for this formulation of dicamba. The use rates with RR2Xtend soybean are 22 to 44 fl oz/A [0.5 to 1.0 lb ae dicamba] for preplant/preemergence applications and 22 fl oz/A for single, in-crop applications.
• EngeniaTM contains a BAMPA (N,N-Bis-(3-aminopropyl)methylamine) salt of dicamba with 5 lb acid equivalent of dicamba per gallon. The maximum use rate with RR2Xtend soybean is 12.8 fl oz/A [0.5 lb ae dicamba] for single preplant/preemergence or postemergence applications. Up to two applications are allowed as a preplant/preemergence and postemergence treatment.

These newer dicamba formulations, while reducing dicamba volatility, do not totally prevent the potential for off-site damage to sensitive non-target plants. Therefore, additional label guidelines have been developed and are required for proper use and stewardship of these herbicide products. The supplemental labeling for these herbicide products should be read and fully understood before making applications. Below are a few highlights of these label guidelines and precautions.

• Be aware of your surroundings relative to nearby sensitive crops and vegetation “AVOIDING SPRAY DRIFT AT THE APPLICATION SITE IS THE RESPONSIBILITY OF THE APPLICATOR”
• May only be tank mixed with products (herbicides & additives) that have been tested and approved for tank mixing [Consult the websites listed on the XtendiMax and Engenia label within 7 days before applying for approved tank mix products; NOTE: as of now no additional products have yet been approved including tank mixing with glyphosate]
• DO NOT apply with products containing ammonium salts such as AMS (ammonium sulfate) or UAN (urea ammonium nitrate) [These additives can increase the potential for volatility defeating the advantage of using these dicamba products]
• Currently, only Turbo TeeJet TTI 11004 nozzles can be used with these products [To control droplet size use within the maximum pressure range allowed by the nozzle manufacturer; consult label websites for other approved nozzle options]
• Optimum wind speeds 3 to 10 mph (max 15 mph)
• Avoiding applications when temperature inversions are likely to occur (i.e. calm wind conditions) is just as important as avoiding applications under conditions of high wind
• Maximum application speed of less than 15 mph
• Boom height less than 24 inches above target pest or crop canopy
• Maintain a downwind buffer of 110 feet or 220 feet (depending on product application rate) to protect sensitive areas. Do not apply if wind is blowing toward adjacent commercially grown dicamba sensitive crops.
• For sprayer cleanout use a triple rinse procedure
• Scout fields before and after application for weed resistance management

In Kentucky, applicators will need to be extra cautious about making an application where sensitive crops such as tobacco, grapes, landscape plants, fruit trees, vegetables, greenhouses or home gardens are growing nearby. There may be some crop field sites where this technology will not be a good fit because of nearby sensitive sites. Applications of non-approved dicamba products on RoundupReady2Xtend soybean are prohibited. 

The availability of this technology provides another tool for managing weed problems in soybean, but we all must practice good stewardship to maintain their availability. The EPA is concerned enough about off-target damage from use of dicamba products, particularly in light of problems from illegal use of dicamba in areas such as Missouri and Arkansas this past summer, that the registrations for use of these products were granted for only two years. Extension of the registrations will depend on whether we can use this technology in a responsible way.