Last I heard, every cropduster takeoff in the U.S. had to be pre-approved by the FAA. That may have changed, and even if it hasn't, I have very little confidence that it has been competently enforced.
MM
Actually there are rules on the books now ,and have been for a long time, that prohibit dropping anything from a plane that could cause property damage or personal injury to anyone on the ground and I guess spraying would be just as applicable. This would be a violation of FAA rules and would get your flying certificate yanked and probably permantly. I am sure that this would also be criminal too and likely a federal offense at that.
I dont know what this planes altitude was but there are also rules about how high you have to be to fly over water craft and populated areas.
I wonder if there are unknown chemical or bio agents that no one knows about right now? If you dont know what you are looking for, how do you test for it?
Maybe the missing AG plane from Florida just showed up!