I know quite a few farmers all over the United States who have tried this and have said the opposite, that they have to use more herbicides, not less. The same holds true with BT.

When we seed millions of acres of land with these plants, what happens to foraging birds, to insects, to microbes, to the other animals, when they come in contact and digest plants that are producing materials ranging from plastics to vaccines to pharmaceutical products?

If your corn has a herbicide-tolerant gene, it means you can spray your herbicides and kill the weeds; you won't kill your corn because it's producing a gene that makes it tolerant of the herbicide.

Jeremy Rifkin Quotes