The way it always worked with full size airplanes & "commercial activities" is if it was done to in an attempt to gain monetarily, then yes...it's commercial. I believe a few years ago when little drones with cameras started appearing, those in ag often said they were going to use them for checking their crops/livestock for irregularities. FAA quickly reacted and said that means commercial because you could gain financially.

But, I don't know anyone on the farmer level that's been arrested, fined or anything yet for flying drones under the wrong circumstance. But, then again, like airplanes, you can go an entire lifetime without ever seeing or hearing from anyone @ FAA.....until you have an accident of some sorts. Or until a neighbor with nothing better to do than worry about things, calls authorities & gets the ball rolling because "some crazy kids are buzzing around my country home with a big drone...with lights on it (sound recently familiar?) and making them feel good by having you forced to cease.

Right now, I'd suspect that existing aerial applicators would like to have you do all the same things they are required to do.