Herbicides used in modern production agriculture are usually not volatile. Those herbicide chemistries that are or were volatile such as the carbamothioates, were largely replaced by other products including glyphosate soon after transgenic RoundupReady traits were introduced and widely adopted. There was limited herbicide volatility in agriculture for several years, due to the low volatility of glyphosate and its near ubiquitous use in major row crops. However, once glyphosate resistant weeds became more prevalent, transgenic crop varieties in soybean and cotton were developed with herbicide resistance to 2,4-D and dicamba. Dicamba resistant seeds had substantially greater market share then 2,4-D resistant seeds in soybeans and cotton. Although new formulations of dicamba were developed and registered for use in dicamba resistant crops, substantial landscape-wide plant damage occurred from off target movement of dicamba.<br/>Widely divergent perspectives emerged as dicamba off target movement occurred in major sections of the United States. Monsanto claimed their Xtendimax products were not volatile, although they later made label changes calling for the addition of a pH modifier to reduce volatility. Post-emergent dicamba applications, especially during conditions of higher temperatures such that often occurs in many sections of the United States, are still contentious. As a result, label changes and other restrictions attempt to reduce the off-target movement of dicamba. Many studies show that some 2,4-D formulations have proven to be less volatile under field conditions and also have less effect on off-target plants.

Herbicide drift and volatility trends

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