I believe at one stage in the '70's or '80's the UKCAA wanted a ban on such activities. The NFU opposed such stupidity and they carried on. However, it was eventually regulated out of existence.
If there is a disease that attacks forests for e.g., and needs to be treated in a hurry, then the a/c will be back in action, pronto.
As for the pilots. "If the flying doesn't get you, the chemical probably will"