White Powdery Mildew Late Flowering

Hi there,
I believe I now see the first signs of white powdery mildew. Nothing too pervasive yet. I’m probably two weeks from harvest. Any advice? Do I harvest early or is the damage done? Do I somehow try to keep the mildew at bay or is that a lost cause as the buds will be tainted regardless?

Do you have any pics of the whole plant?

Hows ur environmental numbers looking?

Solid airflow and lower RH can reduce mold chances. But once it sets it, ur in an uphill battle to rid ur grow of it.

A few growers around here swear by perpxide diluted into water sprayed on. I dont like spraying buds with anything tho. So Id probably bag, then chop the infected area for an inspection FAR from the grow area. (Mold spores spread like the plague).

Pull the removed areas buds open an check for more mold. If u see more? Inspect buds surrounding the area next. If u dont, a thorough bud wash and subsequent dry. Then up ur Mold Preventative Measures.


@kaptain3d had dealt with this a bit and perhaps can share his most successful application


Thanks for the reply. I’m growing outside in the mid-Atlantic US. Temperatures have been fluctuating quite a bit the past couple of weeks. We were in the 70’s last week and back up to 90 this week. Humidity is high.

Here are some more pictures of the affected plant.

This is the area from which I plucked the leaves in my original post:

Here’s the main cola:

Here’s a closer look at the flowers:

Any point in harvesting now?

Is there potential to bring the mildew into my drying environment (tent)?

Thanks. Hoping for some success stories!


A tablespoon of peroxide in a cup of water will instantly wash away WPM: try it on a spot before doing anything else. I believe you are just looking at natural variegation.


That looks like where a snail slug or whatever was on it. I often see those white milky looking spots on my outdoor plants where they crawled on them at night

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Dude its been a crazy year for slugs. I saw the biggest ive ever seen in person almost a month ago. Effer was almost a foot long. Like 8-10 inches. Freaked me clean out. And the number of them is growing as well.


@PurpNGold74 it would really freak you out if you check your plants at night I once had a copperhead curled up in a plant one night, that’s why I no longer check plants at night screw that!!!


Bahaha. Yea whenever we can go outdoors legally, i bet these country ass woods critters LOVE marijuana. Not looking forward to it at all. Creepy crawlies give me the heeby jeebies.


Yeah, definitely more milky looking than powdery. Was wondering about that. Would love that to be slug residue. Thanks for giving me hope!


I once grew a crop or two in purple and gold country but those dang nutria rats cut them down !!!


What helped the most for me was spraying with some apple vinegar cider diluted in water.
2 tablespoons of apple vinegar for 3 cups of water…

But @Happilyretired had a great suggestion. PH the water to 8 - 8.5 to make the solution a bit acidic and make it less prone to WPM.

Hopefully, he will chime in and correct me if made a mistake :wink:


This will take care of it for sure …safe to spray on buds
I actually took a sample of my plant …amd did a bud wash in this …then rinsed it with water …I can report that it did nothing to alter the plants taste or smell in any way …

It’s about $20 on Amazon and I still have more than half a bottle
Ypu dilute with water for whatever your issue
The back has instructions
Use a pump sprayer with continuos mist to coat the entire plant .
It will not burn the leaves …but I would always treat it like any other thing you spray on plants
Late after noon or hours before direct sun

You actually want as alkaline (base) as possible. 8.5 is on the base side of neutral.

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But to be clear hydrogen peroxide is a weak acid. So a weak alkaline is also good!

Still have my fingers crossed this is not WPM.

Thanks for all replies.

Peroxide is a dilute acid that has an unstable O atom that oxidizes organic molecules. Nice because it turns into H2O.

Peroxide and silver wool is used for stabilizing thrusters on missiles FYI. It’s highly reactive.