Dicamba tolerant soybeans … without dicamba

On June 3, 2020, a federal court ruling vacated the registration of dicamba herbicides approved for use in dicamba tolerant or Xtend soybeans in New York. The herbicides named in the decision were XtendiMax, Engenia and FeXapan.  This effectively stops the approved sale and use of these three dicamba herbicides for use on Xtend traited soybean in New York. However, Tavium Plus VaporGrip Technology (diglycolamine salt of dicamba + s-metolachlor premix) was not listed in the court ruling and remains an option for growers to use on dicamba tolerant soybeans.

Unless an appeal to the ruling or an emergency stay is granted by the court, this decision will certainly change many currently planned herbicide programs in place today. The question that will be asked by growers is “I’ve planted Xtend soybeans, now what are my options?”. For soybean growers that have resistant tall waterhemp and palmer amaranth in soybeans there are other effective herbicide options available. For soybean growers that have multiple resistant marestail (Groups 2 and 9) in soybeans it will be more challenging.

The postemergence control of resistant tall waterhemp and palmer amaranth in all soybeans, including conventional, can be achieved by applying Reflex or Flexstar (fomesafen) or Prefix (s-metolachlor + fomesafen) or Warrant Ultra (acetochlor + fomesafen) before the weeds reach 3 inches tall. If necessary, a late rescue treatment of Cobra (lactofen) can be applied.

There are no effective postemergence herbicides to control multiple resistant marestail in glyphosate tolerant (Roundup Ready) or conventional soybeans. Postemergence applications of Reflex, Flexstar and Cobra, will not control marestail.

This court ruling comes at a very poor time during the growing season. There are still many unanswered questions about how this will affect any of these dicamba products that are already purchased and on the farm. The chemical companies will continue to provide updates on this court ruling and what it will mean to growers and retailers. In the meantime, make sure you have an alternative plan in place in case XtendiMax, Fexapan and Engenia herbicides are lost for the remainder of the growing season.

Also published on the Cornell Field Crops blog.