Here's a wild thing: at many of the high end vineyards they'll do low-level helicopter flights over the vines every time it rains to blow the water off the leaves and fruit specifically to prevent infection and rot.
Yep. I recently visited some high end vineyards in Arizona, and the grapes really thrive because of how dry it is. They are able to irrigate carefully to avoid wetting the tops of the plants.
having worked at a cargo drone company, that is one thing that our platform would have excelled at. although ours had a tendency to simply flatten vegetation when "cornering" at low altitude.