There's a new approach that competes with Monsanto's herbicide-resistant crops. Robotic weeding is finally here.[1] John Deere just bought Blue River Robotics for $305 million. They make a unit that's towed behind a tractor. Cameras look down at the plants, and when they see something that looks like a weed, it gets zapped. No need for herbicide-resistant crops.
This is for vegetables and row crops, rather than field crops. It's been used on cotton and lettuce so far. For lettuce, it's weeding as a service. They bring in the machines and do the job at a flat fee per acre. They're doing 35,000 acres in California and Arizona now. This isn't experimental. It's out there working in fields.
Bosch has a similar product. Blue River kills with a spray. Bosch either pounds the weed into the ground or zaps it with a laser.