Growing up on a sheep farm in New Zealand, two tasks that sometimes fell to me were digging out thistles and spraying barley grass. It was important to keep these weeds from spreading, and teenagers were the lowest-cost weed eliminator. In modern agriculture, robots are increasingly being used for weeding. They use computer vision to identify what is a weed and what is not. They have various ways of dealing with the weeds they see; some spray them, some dig them out, and others zap them with a laser.