Recent data from the U.S. Department of Agriculture says that over 90 percent of U.S. field corn is genetically modified. That figure has nearly doubled over the past 10 years.
Most of the corn farmers plant has been embedded with a gene—usually from a bacteria—that protects the corn from pests or herbicides.
Ten years ago, less than half of the corn planted had a genetically modified trait. Today, 93 percent of all field corn does, up from 90 percent last year.
Iowa State University extension agronomist Mark Johnson says that’s partly because the first genetically modified seed successfully fought a bug called the European corn borer.
"The first one was very, very, very effective," he said, "it’s what we call high dose. And so there’s never been any resistance found anywhere. And so that made the adoption of the other ones so much more rapid."
Johnson says subsequent traits for corn rootworm and herbicides haven’t been as successful, leading to resistance in some pests and plants. He says there will always be some farmers who reject genetically modified seed. And as corn prices drop, others may find the math no longer adds up for the expensive traits.