Here is why 100% weed control is so important: A dead weed can never become a resistant weed.
Remember, just a few years ago people would use phrases like, “It’s not economical to spray a herbicide when there are only a few weeds in the field.” If you have sprayed herbicide(s) once or twice in your field and not all the weeds died, either those weeds are resistant or they are becoming resistant. Once they go to seed, you may then be fighting even tougher offspring.