This is thanks to Monsanto, who is now recommending even more toxic herbicides to kill off the monster weeds.
Of course, there's another, more effective and non-toxic way which Monsanto is ignoring:
"In a 2012 study I'll never tire of citing, Iowa State researchers found that if farmers simply diversified their crop rotations, which typically consist of corn one year and soy the next, year after year, to include a "small grain" crop (e.g. oats) as well as off-season cover crops, weeds (including Roundup-resistant ones) can be suppressed with dramatically less fertilizer use—a factor of between six and ten less. And much less herbicide means much less poison entering streams—"potential aquatic toxicity was 200 times less in the longer rotations" than in the regular corn-soy regime, the study authors note. So, despite what the seed giants and the conventional weed specialists insist, there are other ways to respond to the accelerating scourge of "superweeds" than throwing more—and ever-more toxic—chemicals at them."