I am an indoor grower so botrytis is mostly not an issue for me as long as I manage leaf mass and humidity/air exchange, but I have an intense interest in botrytis because I see it everywhere here in New England ruining food crops and flowers with our wet cool falls, and there’s a ton of newer research out there about how to fight it with biofungicides and other IPM techniques, I think the best cannabis study I’ve seen so far is this 2021 Canadian one. It found that while the usual Bacillus subtilis strains are effective, most effective is a newer strain that’s being intensely studied, Bacillus velezensis that has the best effect on botrytis cinerea. I can only find one product on the market so far that uses it, a wettable powder from a Swiss company with a Canadian-based North American distributor:
EDIT: ah, Arbico has it, of course:
Balthazar et al. 2022 Phytopathology.pdf (633.7 KB)