Mildew or Trichromes?

Phosphorous acid (not phosphoric) is sometimes used for powdery mildew on food crops. I pH it with KOH and inject it into some of my fruit trees which are subject to root rot caused by an oomycete. The buffered form of it is known as potassium phosphite.

It should be mentioned that it is probably not allowed on medical cannabis. It is considered a fungicide.

Edit, I was curious whether it was allowed on cannabis or not: There are a number of phosphite and phosphorous acid products on the
"Guide List for Pesticides and Cannabis - Oregon.gov".

It does not appear listed on either California's may use or may not use lists. California mentions "potassium silicate" on their may use list.

Sil-guard is one such potassium silicate product which mentions phosphite as an ingredient.

So, it appears it may be legal.
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SULFUR BURNER! The only way to roll with PM! PM infects your entire grow enviroment. If you treat the plants it's still in the room in the form of micro spores. Unless you want to spray the entire room and devices with h202 sulfur is the o ly way to kill every single spore in every single space.

Also you need to do an h202 bath once you harvest the bud. Cut it, remove most of the undesirable leaves and then dunk everything for a few seconds. I've done it and do it even if I dont see anything wrong. It won't hurt your buds but not only will it remove and kill PM spores it will help prevent mold in the curing process.