Engineering crops with resistance to 2,4-d and dicamba

New herbicide-resistant crops under development by several companies could be available as soon as the 2015 growing season.

Enlist corn is resistant to both 2,4-D and “fop” herbicides used to control grasses. Enlist soybeans are resistant to 2,4-D. The Dow Agrosciences formulation of 2,4-D (2,4-D choline) is less volatile that 2,4-D amine and will be marketed in a premix with glyphosate, called Enlist Duo, for use on Enlist crops, and could be available for the 2015 growing season. Approval of Enlist crops has been delayed by the additional requirement for an Environmental Impact Statement by EPA. Enlist soybeans will be stacked with both glyphosate- and glufosinate-resistant genes as well, which would also allow the use of glyphosate and Liberty herbicides on those crops.

Xtend traits are being developed by the Monsanto Company. These traits confer resistance to dicamba herbicide. This would allow direct application of dicamba to soybeans to help address glyphosate-resistant weeds, as well as alleviate concerns about dicamba drift onto Xtend crops. BASF and Monsanto are developing a new formulation of dicamba with lower volatility than Clarity, which already has lower volatility than Banvel. Monsanto will sell a premix of glyphosate and the new formulation of dicamba under the product name of Roundup Xtend. The new dicamba formulation will also be available by itself under the product name of XtendiMax for Monsanto and Engenia from BASF. Xtend crop technology introduction has also been delayed by the additional requirement of an Environmental Impact Statement. Xtend soybeans could be available as early as 2015.

Dicamba- and 2,4-D-resistant soybeans are not cross-resistant, so application of dicamba on Enlist crops or 2,4-D on Xtend crops would still result in severe injury or plant death. As mentioned above, new formulations of dicamba and 2,4-D are being developed with reduced volatility, but spray drift will still be a concern onto susceptible or non-resistant crops.

For more information, see the related Michigan State University Extension article “2,4-D and dicamba-resistant crops and their implications for susceptible non-target crops” and the AG Professional article “New herbicide-resistant crops under development.”

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