Dicamba: Considerations for Dicamba Alternatives (06/11/20)
Last week, we submitted a supplemental article to Crop and Pest Report that outlines some of the best alternative herbicide options for difficult-to-control weeds in the case where dicamba cannot be applied to Xtend soybeans. We have received further clarification on the ability to use approved dicamba products, but there may still be the need for alternative products on some of these acres. There are a few points I would like to address in more detail for these products.
We highlighted that Group 14 (PPO-inhibiting) herbicides are one of the best alternatives for many weeds. It is important to remember that using a Group 14 herbicide postemergence will require different application parameters than dicamba. It is not as easy as swapping out a dicamba herbicide for a Group 14 herbicide. Group 14 herbicides are contact herbicides and thus require smaller droplets than systemic herbicides like dicamba and glyphosate. Simply put, you will experience poor weed control if you spray Group 14 herbicides through your Xtend soybean spray nozzles. The adjuvant requirements will also be different than those required for dicamba applications. Best control will be achieved by selecting nozzles that produce smaller droplets, increasing carrier volume, and using full rates of oil adjuvants.
The other factor to keep in mind is that many of these herbicides could also be in limited supply depending on how many acres of Xtend soybean we will actually be able to spray with approved products. If you do choose to or need to use these products, it would be wise to start the process of finding products and adjuvants. Lastly, these Group 14 herbicides are contact herbicides and work best when applied to smaller weeds. Weed control will be best on tough weeds like kochia and waterhemp if they are 2 inches or smaller at application.
NDSU publication “Selecting Spray Nozzles to Reduce Particle Drift (AE1246) can provide more information on nozzle selection based on herbicide choice (https://www.ag.ndsu.edu/publications/crops/selecting-spray-nozzles-to-reduce-particle-drift/ae1246.pdf). The 2020 North Dakota Weed Control Guide (W253) has more information on herbicides for postemergence use in soybean (https://www.ag.ndsu.edu/weeds/weed-control-guides/nd-weed-control-guide…).
Extension Weed Specialist
This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.