I spent the last year working at a Distillate farm, huge 10,000 plant greenhouses with evaporative cooling "wet walls" that were completely pointless after about 80°f. There were times I was in the flower houses and they were 100°F+ and 99% RH. Even got to see it raining indoors a few times, micro-climates are fascinating up until you realize it just molded a room with 5000 - 10,000 plants. Mold and/or PM covered just about everything in a room once it got hold. They sprayed a ton of f'n sulfer, hydrogen peroxide, just about anything they could to fight it back to where it was good enough to make it through distillation with being dinged for mold spores or chemicals on the tests. I'm still not convinced that spores didn't come home on me and despite stripping in the garage and spraying myself with 99% ISO every day before coming in the house for a shower. I think I still brought spores home to fuck over my own grow.
Until working at the farm I only had mold once, after starting there I lost two crops to mold and just found PM this week and I quit that job 2 months ago. I culled the leaves and treated everything with Hydrogen peroxide, cleaned the house the whole week from top to bottom, and it seems to be held back, for now. The bottom line is, especially in the south where I am, the spore count is astronomically high this year, as is the heat and humidity. I've got UV-b sterilizing bulb in my AC, electrostatic air filtration throughout the house with a whole house dehumidifier in the AC unit, a standalone unit at the air intake, and a small until in the actual grow.
Last night I stayed up all night tuning my airflow throughout the house to get it below 50%RH in a 5x2 closet. I was able to get it stable at 48% inside while it was 94% outside. Closing my closet and restricting the airflow in the slightest raises it up to around 65-70%.
It's all about environmental controls, the spores are everywhere and the only thing we can really do is be preventative and pay attention at every step of the way. I cut enough huge colas covered in botrytis out of the dispensary grow to no longer have an emotional reaction, but I have yet to find a way to "get rid of it" once its in the plants.
Plants with a high mold resistance, cleanliness, and environmental controls are the keys. I started to have mold problems in 2020 when I switched to using American genetics and started workign at a pro-grow. Brexit and Visa took out my favorite seedbank websites and I really don't want to get back into crypto just to buy seeds, but I'm strongly considering finding a way to get back to the "oldschool" breeders like Serious Seeds, Nirvana, Dutch Passion, etc... because I never once had a problem with those plants.
I'm of the opinion that most American breeders are just throwing genetics together and giving them a cool name for $100+ seeds that have had few to no trials to determine their actual viability against molds, diseases and pests. They're just in it for the cash and don't give two shits if you make it to yield, but if you can run perfect 35-40%RH and keep your temps below 75° all the time you might get a full crop out.
The Euro seeds I ran until 2020 handled environmental variations much better than these American seeds and I'm pretty sure our breeders state-side will blow whatever smoke up your ass they need to in order to sell you overpriced seeds.