Left untreated, severe weed infestations can reduce soybean yields by more than 50 percent. Glyphosate is a broad-spectrum herbicide that kills most broad-leaf weeds and grasses. Genetically engineered glyphosate-tolerant soybeans were commercialized in 1996, and in the years that followed, the share of acres planted with glyphosate-tolerant soybeans and treated with glyphosate increased rapidly.
By 2006, almost 9 out of every 10 acres were planted with glyphosate-tolerant seeds. As glyphosate-tolerant seed use became more common, an increasing number of soybean farmers started using glyphosate as their sole source of weed control.
By 2018, glyphosate-tolerant weeds were identified in the majority of soybean-producing states and were particularly problematic in states located southwest of the Corn Belt, such as Mississippi, Kansas, Tennessee, Arkansas, and Missouri. Herbicides other than glyphosate, such as dicamba, can help control glyphosate-tolerant weeds.
In 2018, about 43 percent of U.S. soybean acreage was planted with dicamba-tolerant seeds. The states with the most dicamba-tolerant seed use were Mississippi (79 percent of soybean acreage), Tennessee (71 percent), and Kansas (69 percent). Notably, there appears to be more dicamba-tolerant seed use in the states with the most glyphosate-tolerant weeds. — USDA Economic Research Service