October 2017
The major herbicidal chemicals used by US farmers haven't really changed very much over the decades. Various forms of 'dicamba', first introduced in 1967, and 'glyphosate', first introduced in 1974 , feature in America's agricultural landscape as much today as they did a quarter of a century ago.
Both these herbicides have a low acute toxicity to animals (you'd need to eat an awful lot before you'd drop dead). However, their properties, modes of action and applications are very different.
Dicamba selectively kills broad-leafed weeds, but not grasses. In 1994, 90% of the 27.6 million pounds of dicamba formulation used in US fields was applied to maize.
Glyphosate kills all plant life. Until the late 1990s, glyphosate was used to clear the ground before a crop was planted, and in 1995 27.6 million pounds of glyphosate-based weedkiller was used in US fields. Since then, usage has increased some fifteen-fold due to widespread planting of GM glyphosate-tolerant soya and later several other similarly-engineered major crops.
In a bizarre twist of fate, glyphosate's popularity has led to a "battle between farmers" and even a farmer's murder, caused by dicamba.