Introduction
Genes that confer resistance in weeds and/or crops to most major classes of herbicides have been identified by academic and industry research teams.
Various combinations of herbicide-resistant genes are being introduced incrementally into major field crops, and especially corn, soybeans and cotton. The mostly important, newly developed, dual-resistance products are discussed herein.
But the major, new GE-HR traits expected to dramatically alter the herbicide market in the next five to 10 years are resistance to glyphosate plus dicamba, and glyphosate plus 2,4-dichlorophenoxyacetic acid (2,4-D).
Both 2,4-D and dicamba have been widely used for decades, as shown in figure below. Both are relatively high-risk herbicides just recently approved for post-emergence applications on herbicide-resistant GMO soybeans, corn, and cotton. These two herbicides will account for most of the growth in overall corn and soybean herbicide use in the next decade, as clear in the trend tables that follow later in this section.
Three post-emergence labels for dicamba have now been granted. The Bayer/Monsanto glyphosate plus dicamba formulation, called XtendiMax, contains the diglycolamine (DGA) salt of dicamba. The XtendiMax label was originally approved by EPA on November 9, 2016. A similar glyphosate plus dicamba herbicide, FeXapan, is manufactured by DuPont and won EPA approval on July 23, 2015.
He projected that dicamba would soon become the world’s second largest selling herbicide, behind glyphosate.
BASF has registered Engenia, the N,N-bis-(3-aminopropyl) methylamine (BAPMA) salt formulation of dicamba, formulated with glyphosate.
The Engenia supplemental label was approved by EPA on December 20, 2016. Limited field research suggests that this BASF herbicide has the most effective combination of technologies designed to reduce dicamba volatilization and drift, and hence off-target crop damage.
The dicamba resistance trait was developed by the University of Nebraska in 2005. At that time, Monsanto was still downplaying the potential for glyphosate-resistant weeds to pose significant or new weed management challenges (see Dill, 2005 for example).
Prior to its acquisition by Bayer, Monsanto projected that dicamba-resistant soybean seed sales in the US would account for about two-thirds of national soybean acreage by 2020. The spread of several, serious glyphosate-resistant broadleaf weeds has created the demand for glyphosate-dicamba herbicide mixtures, and the accompanying GMO seeds.
Remarkably, Brett Begemann, Monsanto’s President and COO, announced in a 2016 “Whistle Stop Tour” presentation to investors that the company would eventually convert its global, ~350 million acre “Roundup Ready” platform to Roundup Ready Xtend (i.e., glyphosate-dicamba HR varieties).
He projected that dicamba would soon become the world’s second largest selling herbicide, behind glyphosate.
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