A good example of such a crop is GM cotton, which is often grown in the United States for cottonseed oil. lf a crop can kill pests, the farmer does not have to spray so often to kill pests.An exarmple of a pest-resistant crop is maize,which is similar to corn. There is a bacterium in the soil which produces a poison that kills insects , but it harmless to people. Putting this bacterium gene into maize plants makes them produce their own poison, which kills the pests that eat them. This is better for the environment because it reduces the need to spray fields with pesticides and fertilizers.