The cropdusters have to be one of the most common GA ACFT that fly low, often fly non-standard circuits and will keep operating under a low overcast and be rather allergic to radio use
In my experience, the croppies generally fly so low as to not be an issue!
I recently sat on the ground with the prop turning, waiting for the cloud to lift off the tree tops and get somewhere near the 300' ceiling that would make my departure legal. While I waited, the local croppy departed and returned several times.
BC 