G day ! Here in Ontario we’ve had a very Humid summer and powderey mildew has been a real issue. I have a few 9ft beauties that are under attack. Been growing for years outdoors so I’ve seen it but never like this! My first 2 sprays were with a Hydrogen Peroxide/Water mix. Pretty ineffective. Any suggestions as to.what I might try next? The buds are big and beautiful but we’re still 3 weeks away from Harvest so I refuse to throw in the towel!
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Watching this topic, sorry I’m not helping.
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Only thing I can think is Athena powder mildew control. Need to reapply weekly tho til it’s under control and get under leaves and all it’s a pita but seems to work rather well. Peroxide wash works also but I have to do that like every other day or so wpm is a biotch take as many interior leaves out as u can before u spray and make for some better airflow also. I’m gonna stay watching also as I have fought this battle in my spare bathroom last grow but since changed around some exhaust tubes to different areas
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How much water to peroxide did you use and how ofter.
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You could try this …
Not sure if they sell it in Canada
It would definitely work
AgroMagen, GrowSafe Bio-Pesticide, Organic Natural Miticide, Fungicide and Insecticide, Non-Toxic, Concentrate (8.5 Ounce) https://www.amazon.com/dp/B07M983TRL/ref=cm_sw_r_cp_api_glt_fabc_XYPPTJADGB6YSKMTAMBX?psc=1
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This is one I’ve seen shared by a couple people stating they had great results. I’m actually making some this morning because WPM wiped out half my veggie garden and it’s lightly spoting up on my girls
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Depending how bad it is, it becomes a nightmare, I’ve battled it to the end just to find out it was throughout the buds as well. Ended up burning it. If It gets bad it seams like it gets into the plant and there is no getting rid of it.You may need to spray every 3 to 4 days to try and keep this under control.I also have been outdoor for years and have tried so many products and when your in the flower stage you need to be careful as well. In flower I use Regalia and peroxide, Good luck…
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@Trichrome66 I’m in south Eastern Ontario and it’s been a not so optimal season for growing.
I had some WPM start last week on one of my smaller girls that was cloned back in June from one of my 8’ ladies. I just mixed up some 3% peroxide and water and used a cloth to wipe the affected fan leaves. Hadn’t moved to the bud, and that did the trick. Removed a few of the fan leaves as well.
Question for you, have you defoliated through flowering?
From the way you have explained in your post the buds/colas are affected? If not, I would do a big defoliation removing affected leaves. Not optimal, but worth it I would say at this point, as like myself, you are very close to the finish line.
Hope you get your issue under control. Can’t offer any experience with other sprays or methods sorry, but I will watch the post to see what other more experienced (than myself of course - 3rd season growing outdoors and loving every day of it) outdoor growers suggest.
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Seems to be happening to a lot of us 
. I spotted a couple leaves on one of my girls had a little WPM forming. I had lost a whole plant in the past so that little white spot caught my attention.
After great advice from the experts on here and some Google . I removed the affected leaves and then some. Sprayed with peroxide/ water I used a 1:4 ratio. Added 2 more fans for airflow, I think I have it under control for now 
Good luck 
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There is a few posts about using milk on mildew. It alters the ph and kills it apparently. I would have another look at the ratio you used for your peroxide as well. I would increase it as you have nothing to lose 
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UPDATE. In the last 7 days I have…
- Relocated plants to a spot that I would
best describe as a wind tunnel. Also
better sun exposure. Not an easy task
moving big plants! - Pruned plants from the inside out
removing approx 1 foot of lower
growth - I’ve hand sprayed twice with a 4:1
Peroxide spray takes approx 2 hrs
per plant - Sprayed once with a Baking Soda,
Dish soap spray - Girlfriend has twice given them Reiki
White Powdery Mildew is a formidable
opponent but I am happy to report that
I am seeing a lot less of it and can likely
begin spot spraying - It takes a ridiculous amount of work.
- I think the pruning, relocation and hand
spraying have done the trick! My
girlfriend thinks it’s Reiki . Lol
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