California farmer Erik Freese pulls down a healthy ear of corn that has been genetically engineered to produce its own pesticide. He says genetic engineering has helped him to farm more sustainably. Kathleen Masterson for NPR hide caption

itoggle caption Kathleen Masterson for NPR

Scientists say the corn rootworm is growing resistant to Bt corn. Snbetor via Flickr hide caption

itoggle caption Snbetor via Flickr