Current status of new herbicide-resistant crops
In the near future, producers will have access to several new crop cultivars with resistance to a wider range of herbicides than has been available until now. These technologies are tools that will help growers combat herbicide resistant weeds. Here is a brief summary of these new crop cultivars and when they are expected to reach the market.
Inzen grain sorghum. K-State released to sorghum breeding programs a line of grain sorghum that is resistant to ALS herbicides several years ago. DuPont assumed ownership of the technology and those seed companies that signed agreements with DuPont will be developing Inzen sorghum hybrids. Currently companies developing hybrids are Pioneer and Advanta. DuPont also is developing the ALS grass herbicide “Zest,” which is a liquid formulation with nicosulfuron as the active ingredient, for use with these new ALS-resistant grain sorghum hybrids. When commercial Inzen hybrids are on the market producers will have new opportunities for postemergence grass weed control. DuPont intends to have herbicide registration for Zest completed in time for use on the 2016 sorghum crop. Hybrid availability for 2016 isn’t known at this time.
Enlist corn, soybeans, and cotton. Enlist traits are being developed by Dow AgroSciences. These traits confer resistance to both 2,4-D and aryloxyfenoxypropionate (the “fop” grass herbicides) in corn, and 2,4-D resistance in soybeans and cotton. Dow has developed a new formulation of 2,4-D called 2,4-D choline, which is lower in volatility than 2,4-D amine. This new formulation will be marketed in a premix with glyphosate called Enlist Duo. This premix will be intended for use on Enlist crops, and has just received a full Section 3 Federal label.
Enlist soybean, corn, and cotton traits have been deregulated by the U.S. Department of Agriculture. However, certain export markets have not been approved yet, so commercial availability is not yet known. Enlist cotton likely will be commercially available in 2016 and Enlist corn and soybeans could potentially be available for the 2016 growing season if key export markets are approved. Enlist soybeans and cotton could alleviate concerns about drift onto the crop from adjacent applications of 2,4-D. Enlist cotton and soybeans will be stacked with both glyphosate- and glufosinate-resistant genes as well, which would also allow the use of glyphosate and glufosinate herbicides on those crops.
Xtend soybeans and cotton. Xtend traits are being developed by Monsanto Company. These traits confer resistance to dicamba herbicide. This would allow direct application of new formulations of dicamba to soybeans and cotton to help address glyphosate-resistant weeds, as well as alleviate concerns about dicamba drift onto Xtend crops. BASF and Monsanto are developing new formulations of dicamba with lower volatility and drift potential than Clarity, which already has lower volatility than Banvel. Monsanto will sell a premix of glyphosate and a new formulation of dicamba under the product name of Roundup Xtend. A new dicamba formulation will also be available by itself under the product name of XtendiMax for Monsanto and Engenia from BASF. Like Enlist crops, Xtend cotton and soybeans have been deregulated by USDA, but their availability for 2016 is still uncertain because of foreign market and herbicide registration approvals.
Note: Dicamba- and 2,4-D-resistant soybeans and cotton are not cross-resistant, so application of dicamba on Enlist soybeans or cotton or 2,4-D on Xtend soybeans or cotton 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.
HPPD-resistant soybeans. GMO soybeans with resistance to the HPPD-inhibiting class of herbicides are in development by both Bayer and Syngenta. No HPPD herbicides are currently available for use in soybeans, so this would provide a new mode of action and allow for greater diversification of weed control options to help manage herbicide-resistant weeds. HPPD-resistant soybeans have been deregulated by USDA, but matching herbicide and export approvals must be in place before the technologies become commercially available.
Dallas Peterson, Weed Management Specialist
Curtis Thompson, Weed Management Specialist and Extension Agronomy State Leader