Just googled drone pictures and found a couple. I would think we need to see it used in swarms also, 6 or more in field at one time:
https://www.bing.com/images/search?q=drone%20spraying%20pictures&qs=n&form=QBIR&sp=-1&pq=drone%20spraying%20pictures&sc=0-23&sk=&cvid=1DEAAC14A1824B6188129CA83335FC2A