While nearly the same amount of corn and soybean acres have been planted every year since the mid-1990s, the use of pesticides in Illinois has increased exponentially, according to USDA data.

Synthetic pesticide use has been a dominant agricultural practice since the 1950s, but use escalated dramatically in the mid-1990s when Monsanto, now Bayer, first released its Roundup Ready soybean and corn seeds, which allow farmers to spray directly on their crops, killing weeds without harming their harvest.

Before the commercial release of the genetically engineered seeds, glyphosate, the main ingredient in Roundup, accounted for a fraction of a percent of the total herbicides used on corn in Illinois. But by 2010, just over a decade after the commercial launch of glyphosate-tolerant corn seeds, glyphosate use accounted for more than 28% of all herbicides used.

That’s because after only five years of commercial use, dozens of weeds had evolved widespread resistance to glyphosate, becoming what some call superweeds. In response, farmers used more of the herbicide or switched to other products, such as 2,4-D and dicamba.