asphalt said:

I guess the powdery mildew is a separate problem. Does that stuff grow on the flowers as well or does it stick to the leaves only?

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Powdery Mildew presents somewhat differently outdoors - it will look sort of like a whitewash on the leaves. It has to stay pretty moist for it to progress to the obvious 'powdered sugar' appearance common indoors. This may be due to excessive morning dew, usually doesn't penetrate flowers unless, it stays damp. If you have good to great sun exposure and a not too dense canopy, you hardly ever see it outdoors.

There are a few really safe methods for dealing with PM - A weak solution of milk in water shifts the leaf PH enough to eradicate the problem if caught early. You will find many threads on the topic here.

Botrytis is another thing, entirely. You have to treat it like cancerous tissue that metastasizes. If you plan on any salvage, it has to be harsh and immediate. Your health isn't worth the science experiment to find out what happens when you consume contaminated produce. So you have to examine each cola under bright light verify all the way to the stem ( Bot seems to bloom from the stem, out into the flower mass ) before putting up to dry. If it isn't isolated to small areas, you really need to toss the entire cola. For some folks (immune suppressed, etc.) none of that grow should be considered safe. I don't think there is any acceptable way of eliminating the contamination ( various concentrate processing methods, etc. ).

asphalt said:

What do they spray in the valley as prevention and when in the grow cycle do they spray it?

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This depends on the crop - and the vector. We have insects here that will spread stuff like Bot.

Potassium bicarbonate-based fungicide has been proven to cure and prevent powdery mildew, blackspot, downy mildew, blights, molds and other plant diseases, such as Botrytis cinerea. Green Cure is an example of such a fungicide.

For cannabis, you really have to limit treatment and prevention to pre-flowering. Once you start getting bud formation and the stigma emerges from the calyx, most treatments will discolor and stunt the emerged stigma. It may take days for flowering to pick back up.

This is what it means to be a 'farmer'. You have micro-climates and unanticipated visitors. One year, we had white moths. And not long after, a bunch of stoned worms making their way through dank buds. And their wake was Bot infections. This year, it seems the duck and chickens ate the moths and kept that shit down. Nothing like watching a duck chase a moth through the cannabis patch. Good times.