Post-Emergent Weed Control in Xtend Soybeans – Slow Down and Be Careful

The future of side by side soybean fields using different herbicides is here with Xtend soybeans commercially available in 2017.  Having more herbicide tools to combat the herbicide resistant weeds is important, but careful use is critical, to prevent crop damage and stay friends with our neighbors. Here are a few things to consider:

  • Non Xtend soybeans (and other crops) are easily damaged by dicamba – dicamba on sensitive crops always causes crop damage with very dramatic looking symptoms. As glyphosate -tolerant soybeans made up the majority of acres in the past and usually only sprayed with glyphosate, drift went unnoticed. The addition of Xtend soybeans to the cropping mix will be a reawakening to anyone who has gotten careless.
  • Should your pre-emergent application have been the one that included dicamba? – preferred timing for dicamba containing herbicides for use on Xtend soybeans is pre-emergent. Research has demonstrated the critical weed-free period in soybeans is emergence to the third trifoliate, early weed removal provides the greatest yield potential. Additionally, dicamba provides residual control for some weed species during that critical period. Another important point is, chances of application mistakes like drift on sensitive crops are greatly reduced during pre-emergent applications.
  • Only use herbicides specifically designed for the Xtend system – do not tank mix dicamba and glyphosate that you might have on hand in an attempt to make “homemade” herbicide for Xtend soybeans. The herbicide manufactured is designed specifically for use in Xtend soybeans, with reduced levels of volatilization, to prevent herbicide drift. Keep in mind the reports on the U.S. experience in 2016.  Homemade concoctions are a very bad idea, plain and simple.
  • The label is your friend…follow it! – the labels contain important information that will help minimize chances of accidental herbicide drift onto susceptible crops. Key points include:
    • Use nozzles delivering extremely coarse to ultra coarse spray droplets (volume median diameter of 450 microns or more) as defined by ASABE standard S572.1 and as shown in the nozzle manufacturer’s catalog.
    • Do not apply:
      • when risk of severe temperature fall in the night;
      • under high humidity, temperatures above 30oC, or fog conditions, to prevent drift to sensitive crops;
      • when wind is blowing toward a nearby sensitive crop;
      • when winds are below 3 km/h or above 15 km/h.

Source: Guide to Field Crop Protection 2017 p. 163

  • All soybeans look alike – know what field you are in – there is no way to visually discern between the different types of soybeans. When in doubt, make sure that the applicator is in the right field. Herbicides specifically designed for the Xtend system applied to Roundup Ready or conventional soybeans will cause significant crop damage. Additionally, knowing the types of soybeans in the adjacent fields is important to indicate increased risk for off target crop damage. Remember, dry beans look like soybeans from far enough away….never make assumptions.
  • Sprayer cleanout requires careful attention – If producers are growing two or more types of soybeans on their farms, careful consideration has to be given to sprayer cleanout as they move between soybean fields. Even a small amount of dicamba will serve as a contaminant in the next spray load being applied, causing significant damage. Especially if you have only grown Roundup Ready soybeans in the past, recognize that the situation has gotten more complicated.

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