Warren, there has to be some discrimination. Weeds sometimes grow IN the rows, and they have to be deleted somehow. So the pattern recognition software would have to take that into account. But it's not too difficult to tell a weed from a crop plant. Okay, maybe it's hard to tell shatter cane from corn or milo (sorghum), but that would be a worst case scenario. For the most part it's pretty easy to tell what is a weed. Of course, you wouldn't want your corn programmed robots invading a soybean field and mistaking the soybeans for weeds, but a little creative engineering would make that a non-problem. It's all in your focus.

If you don't care for reality, just wait a while; another will be along shortly. --A Rose