Johnson Grass
This weed has become very annoying the last eight years. It all started when in July our egg plants and peppers were being swamped by this grass. Up until that point the crop was clean of weeds. The weed was evenly distributed over the whole crop. Our suspicion was immediately on seeds brought in with the irrigation water from the canal. After investigations by our water tender on the canal he reported that there was a weedy patch on a farm ahead of us in the canal that had been cut a month before.
Now we are still living with this problem even though we get a warning from the water tender if the offending farmer is putting seeds. In the peppers we have wonderful crop with the grasses growing above it. There is no way we can even get in there with hand hoes. My thesis at college was on weed control without herbicides, and at the time a company in Texas was working on an electric weeding machine. This consisted of a copper tube in front of the tractor that was set above the crop but low enough to contact the weeds. A generator was attached to the tractor power take off (pto). A metal wheel behind the tractor touched the earth to complete the circuit. The weeds steamed as they made contact with the copper. Unfortunately I have been unable to find any mention of the machine since the mid 80's. It does sound like a potential safety nightmare but was very effective.