Jun 08, 2020

Weed Control in Soybeans - BMP’s for Weed Management - Without DICAMBA 

The recent actions by the Federal Court ruling revoking the federal registrations of certain dicamba products in Roundup Ready® Xtend Soybeans, also known as dicamba-tolerant soybeans (DTS) has created quite a stir in the ag industry.

We have done this before and we can do it now.  Remember that dicamba was/is only ONE TOOL of the weed management system.  We KNOW THE PRODUCTS to use in place of dicamba and WE KNOW HOW TO APPLY THEM.  Let’s modify a planned full-season pest management program, remember proper weed management practices, change our application practices to best maximize the products we can use, and effectively go out and control weeds!

Key Steps to Effective Soybean Weed Management without Dicamba Herbicides 

Primary weed control for managing weeds without dicamba in the DTS System will likely require effectively using and managing PPO HERBICDES, and will require using higher labeled rates of GLYPHOSATE, always including an effective RESIDUAL and using the correct ADDITIVES. 

PPO Herbicides For Effective Weed Control Without Dicamba:
Flexstar Herbicide or Sinister (fomesafen)
  o Registered under full federal label for use east of US Hwy 281 in SD and ND
  o Registered under Section 24c Special Local Needs labels in SD and ND for use west of US 281 west to the SD Missouri River on a north-south line and similar geography in ND.  Specific counties are on each product and state-specific 24c label.  
  o Significant label restrictions are on the 24c registrations and these MUST be followed 
Flexstar GT Herbicide (fomesafen plus glyphosate)
  o Only registered for use east of US HWY 281. Not covered by The SLN Section 24c’s
Avalanche Ultra or Ultra Blazer (acifluorfen)
Cobra (lactofen)
Resource (flumiclorac-pentyl)
Prefix (fomesafen + S-metolachlor)
Warrant Ultra (fomesafen + acetochlor)
Anthem Maxx (fluthiacet-methyl and pyroxasulfone) 

Non-PPO Herbicides For Additional Effective Weed Control Without Dicamba:
Basagran (bentazon).  Can be effective, but often requires two applications.
FirstRate (cloransulam-methyl).  Can be very effective for marestail control.  Rotational restrictions are a concern.
Pursuit or Extreme (imazethapyr or imazethapyr + glyphosate)
Raptor (imazamox)
Varisto (combination of Basagran and Raptor)

Application and Equipment Setup: Keys to Successful Weed Management With PPO  
Keep Weeds Small.  Post-emergence herbicides in soybeans are by far the most effective when applied to small (<4”) weeds.  Shorter weeds have fewer growing points.  
Change Nozzles Away From Dicamba Nozzles.  PPO herbicides are contact herbicides, not systemic like dicamba.  Coverage is critical to success.  Choose flat fan AIXR or similar as good choices for smaller sprayers or move to Wilger MR or ER type vs Wilger DR on systems using these.
Increase Water Carrier Rates. Contact herbicides require greater water volume! 15 GPA is the MINIMUM for successful application, 20 GPA is much better.  This is NOT optional!
Manage Drift.  PPO Herbicides are still susceptible to particle drift.  Spray mist will show speckle up anything it touches.  Use drift and deposition aides like Interlock or similar to help control fine droplets.  A DRA is NOT recommended, as we do not want to sacrifice coverage, just control fines. 

Herbicide and Tankmix Considerations: Keys to Successful Weed Management With PPO
Use Full Rates of Post-Emergence Herbicides to Maximize Control.  Full rates of the PPO herbicides will increase effectiveness of control with the first application.
Use Overlapping Residual Herbicides.  Pre-emergence herbicides provide 4-6 weeks of residual at maximum.  Later-emerging weed flushes like waterhemp require additional residual.  The only PPO with any significant residual is Flexstar, and it is not long enough to get us through full canopy.
  o Warrant, Dual Magnum (or other S-metolachlor), Zidua and Outlook will be needed.
  o FirstRate can be effective for marestail; however, be aware of rotational restrictions
Maximize the Non-Selective.  Use increased label rates of non-selective products like glyphosate
Additives matter!  Use of AMS water conditioners is allowable.  Non-AMS conditioners can also be effective.  Most PPO Herbicides also require an OIL- Use an effective HSCOC like Superb or HSMSO like Destiny or Zaar.  Improving deposition and drift management with products like Interlock or similar can improve application effectiveness. 

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