Herbicide and Pesticide Spraying UAV?

What would be an application in the UAV/UAS world that would revolutionize agriculture? There are lots of answers I'm sure, depending on who you ask. 

One area that seems, to me, to be a significant area of application is that of spraying herbicides and pesticides. With a UAV it would be possible for precise application that could be done in a variety of conditions. No more waiting on the ground to dry out so that you can run a spray rig over it. No more calling the local aerial applicator and getting on their waiting list.

Let's look at a real-world example. Suppose you have problem with herbicide-resistant weeds, specifically Pigweed (Amaranthus palmeri). Right after a period of rain, the seeds that have been scattered by the wind are apt to really take hold and sprout quickly. You catch the problem patches in many of your fields because you are able to make a quick round of flights with a UAV, spotting invasive patches of these destructive weeds in their infancy. If you can get a herbicide on them early they can be more easily killed. If you wait more than a few days, likely they will be tough to get rid of, time to get the hoe out. So your options are to get out your sprayer or call the aerial folks to get the problem fields sprayed immediately. Option one is a no-go, the fields are still too wet to travel on. So you call the aerial service and get on their waiting list. May end up being a few days before they get to you, plus you will probably get a little more broader spray coverage than you really need. By the time the herbicide gets there, it may be too late. Too bad you don't have a UAV capable of spraying herbicide. If you had one you could make note of the GPS coordinates of the problem areas, take the UAV to the field, fill it up with some herbicide and water and then let it take care of business. The weeds could be eliminated a matter of hours after sprouting. 

Currently the application of herbicides or pesticides via UAV or even remote-controlled systems is not permitted. As technology develops and safety features improve, expect to see UAV systems spraying herbicides in a field near you.

I dug up a couple of videos of these sorts of applications.

Here is one showing a small multicopter doing some lighter spray work. Ideal for small farms, wineries, orchards and vegetable farms.

Here is a much more "industrial" unit. This copter is capable of much larger payloads and coverage of larger acreages. It appears that this sprayer is still remote-controlled, but autonomous control would be easily attainable. 

Look for UAV applications such as crop spraying to materialize in the U.S. within the next decade if not earlier. Safety is key. More precise application, less chemicals, improved coverage and quicker response times are clear advantages!