Powdery Mildew (https://overgrow.com/t/powdery-mildew).
Hi all. I’ve been having some great success with managing the Powdery Mildew(PM) infestation on my small outdoor crop this season with this method. It is a bit harsh, maybe, but mother nature doesn’t rest.
If you try this method you will need some or all of the following items. It will blow your mind too.
Cannabis with Powdery Mildew. This is essential.
3 Buckets
3 Spray bottles (photo shows two)
Syringe or measuring spoon
Hydrogen Peroxide
Milk
Distilled Water
Fan
LAB (Lactobacillus Serum)
2 good Oscillating Fans or Floor Fans
Hand sprayers are great for a larger crop/plants for the washing and applying of Milk and Distilled Water.
No pics of the Hydrogen Peroxide Steps.
This is important. You want to dilute the 3% Hydrogen Peroxide down significantly. You do not want to spray your plant and see it fizz or bubble up. If that happens you are loosening up more than just the PM, trichs loosening and potentially bleaching the leaves.
In a 32fl oz/.95L spray bottle mix Hydrogen Peroxide and water. (Regular ol water that you pour in your mouth will work). Not a lot of science here, just add about three or four tablespoons Hydrogen peroxide to the bottle then fill with water. Find the PM and gently but aggressively spray the PM spots directly with the spray nozzle set halfway between jet and mist. Let it sit for several minutes then start washing it off with another bottle of plain ol water.
Some of the leaves will show spots of PM still, but a lot of the spores are now dead and your plants leaves are clean. Again, no science here, but I’m going to make that claim. 
Now it’s time to get some major air flowing. For hell’s sake you just sprayed your plant with water??? WTF??? right? Just wait for this one.
Next we’re going to start blasting our precious flowers with milk.
For this part I re-enacted the process in the morning sun then clipped the flower. I’d suggest doing this at dusk just before the sun fades into the night.
250ml 2% Milk
15ml LAB(Lactobacilllus Serum)
Now go spray your buds with this concoction.
Let it sit on the flower for 10 or so minutes. Gently ruffle the stalks around so the milk works its way into the flowers and surrounding leaves below.
With DISTILLED WATER. It must be distilled water. We want to spread that LAB around to let it grow, but also wash off the majority of milk so little “Cups” of milk residue are left on the leaf tips.
In the morning after you’ve had fans running on them all night, your leaves should have a shiny shimmer to them and a slight odor of milk. Not sour milk, just milk.
I saw a huge decrease in the PM infestation overnight!
This didn’t get REMOVE it completely. There is info online about what and how PM grows and disperses. For the last step it involves the buckets, Hydrogen Peroxide and Water.
Harvest the way you normally would. This pic shows the milk from the re-enactment.
Trim it up loosely.
Then we give it a Hydrogen Peroxide Bath.
Again, NO FIZZING OR BUBBLING. Add about 460ml of Hydrogen Peroxide to 5 gallon bucket full of tap water. This dilutes it down really well and no fizzing or tiny bubbles appeared for me.
Most of the leaf matter is from earlier harvesting. I promise this will really blow your mind when your doing it. It is a strange feeling. Give it a few dunks and hold it under water until you see all the little air bubbles float up to the surface. I dunk them pretty aggressively, but gently too. We are saving the flowers so try not to shake the PM off them. A good dunking for about 15-20 seconds.
Then we rinse off the majority of the Hydrogen peroxide in the Second Bucket we set up. This bucket is straight tap water from my hose. Notice almost no leaf matter. All the little trim is just floating there allowing more air to flow through the newly trimmed flowers.
And the last bucket is plain water as well for good measure. So three buckets total. I made fresh buckets at the start of each plant harvested. You can skim the shake off the top, and run it through the water buckets as well, and dry it or put through a hash sieve I would imagine. I’m making tinctures with it.
Now that you have a bunch of wet bud hang it in front of a fan for a few days and cure as normal. Hope this helps someone. I know it all seems weird, but it has been working.
Try not to let the milk sit on the flowers. You can see in the last photo there is a little white stuff on the bud closest. You have to be pretty meticulous, but you would have had to have been in the first place. Good luck.