Monsanto's Roundup Ready 2 Xtend™ soybean, which is tolerant to both glyphosate and dicamba, is available for purchase this spring. While this will eventually offer another option for controlling glyphosate resistant and other tough-to-control weeds, it also brings up label and marketing concerns for the 2016 growing season.
Dicamba is NOT labeled for use on these soybeans for at-planting or postemergence applications. It is currently labeled ONLY for preplant burndown applications and those require a wait time of 14 to 30 days before planting, even if the variety is tolerant. Any other applications to soybean are in violation of federal and state law and may result in enforcement actions, and additional liability to the producer for off-target movement. Low-volatility dicamba formulations for use with tolerant soybeans are still awaiting approval and it's unlikely approval will be granted in time for this growing season.
From a marketing perspective, there are additional concerns. Monsanto announced in February that China will allow imports of the dicamba-tolerant soybeans. However, while the glyphosate and dicamba-tolerant traits have individually been approved in the European Union, the "stack" has not. The approval process for the combined traits is in its final stages in the EU and while the company expects a favorable outcome, it is not guaranteed. This may affect marketing in the fall. Growers should check with their grain handlers to confirm whether or not they will be purchasing dicamba-tolerant soybeans this fall.
Use an integrated approach
Due to the uncertainty with the herbicide labeling, growers planning to rely on the dicamba system to control glyphosate-resistant weeds might want to look at alternative strategies. Options might include rotating to a different crop or planting a LibertyLink variety and applying glufosinate to control the problem weeds. As always, an integrated approach that includes both chemical and non-chemical strategies is essential for managing difficult weeds, seedbanks and herbicide resistance.