Source: NCSU COOPERATIVE EXTENSION, 6/10/20


Hopefully you had the opportunity to purchase your dicamba products prior to reading this blog. If not, you may be wondering, “what can I spray on my dicamba soybeans or cotton to control my Palmer amaranth, common ragweed, or other troublesome weeds?”. In most areas, we can still control glyphosate-resistant weeds with conventional herbicides in soybean, however there are some areas of the state with both ALS- and PPO-resistance. If you are in an area with confirmed or suspected resistance to ALS- and PPO-inhibitors and you do not have approved dicamba products prior to planting Xtend soybeans, you may want to consider switching varieties to those containing Enlist or Liberty Link traits. If you have planted Xtend soybeans or cotton, your options follow.

First, a reminder and a call to reason. Only dicamba formulated as Xtendimax, Engenia, Fexapan, or Tavium may be applied over the top of Xtend soybeans and cotton. You can do so until July 31st if you currently have the product. Now, if you do not currently have approved dicamba products, don’t panic and for God’s sake, DO NOT APPLY ANY OTHER FORMULATION! We have options, and using products off label will only increase the chance for off target issues and shine a negative light on us.
Soybean Weed Management without Dicamba:

Now about controlling those weeds if you planted Xtend soybeans, but do not have dicamba. Xtend soybeans are tolerant to glyphosate and dicamba. We can still effectively use glyphosate to control grasses, sicklepod, sedges, and cocklebur – to name a few of our challenging weeds. To control glyphosate-resistant species such as Palmer amaranth and common ragweed, use the following approaches:

Palmer amaranth: start with a strong residual program with Group 14 (PPO-inhibitors) and Group 15 (chloroacetamides) herbicides.

This should be common practice by now for all soybeans, but will be critical to stay ahead of Palmer amaranth. Metribuzin (Group 5) is also an option PRE, but follow precautionary guidelines to avoid soybean injury. Most Palmer amaranth is resistant to ALS-inhibitors across the state, so we will have to rely on PPO-inhibitors such as Cobra, Flexstar, Reflex, Resource, or Ultra Blazer for POST control before they reach 4 inches in height. Add in an overlapping residual product (Group 15) to control subsequent flushes. Be prepared to follow a up with a second POST if needed.

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