Powdery Mildew - How best to treat?

Grow info below. Found powdery mildew setting in on multiple leaves and cut them off. Found only one bud that had started to rot and got rid of that also.

Am reading that milk and water, baking soda and water, or vinegar and water are effective treatments (I would prefer a natural solution as the plants are well into flowering). Any insights from those who have successfully fought off this pestilence?

  • Afghan Kush from World of Seeds
  • Method: Potting soil
  • Vessels: 4 gallon Pots
  • PH of Water, Solution, runoff (if Applicable): Brita filtered local tap water, source pH approximately 7.0
  • Outdoor
  • Light system n/a
  • Temps - 70-90 day, 55-75 night
  • Humidity varies
  • Ventilation system n/a
  • AC, Humidifier, De-humidifier n/a
  • Co2: No


Just FYI, peroxide is a naturally occurring chemical that breaks down very rapidly into water and oxygen.
It occurs in nature and we even have it in our bodies in trace amounts all the time.
I use it to treat mites.


60 % milk 40% water

Spray plants and the film left from milk will act as antiseptic and also a barrier for future problems

If I’m not mistaken right before lights come on so that way it dries on your plant


Thanks folks. Just applied a baking soda solution, as that seemed the least intrusive means this far into flowering. I’ll see what they look like when it dries. I’ll keep a very close eye all the way through the finish line and hopefully to the medal ceremony, LOL.

Both of these are probably already in your grow room:

–H2O2 and water
–Mycorrhizae and water

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How much baking soda? Did it get into the medium?

Most people use hydrogen peroxide and water as their first treatment. It’s just water with an extra O molecule and water. That extra O molecule drowns pathogens with too much oxygen.


I used a half tablespoon of baking soda per quart of water. Sprayed two quarts onto the three plants. Soil is OK, no issues there.

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Yes, but adding too much salt (baking soda) could cause issues. If the solution got too much into your medium, you might run into salt and pH issues. Be careful!


Ah, gotcha. I used a small mister to spray the plants so I don’t think much of it got into the pots, but I’ll give them a water flush just to be safe. I’ll hit them with peroxide solution tomorrow.

This far about 10% of the pistils have turned red/brown, so I’m hoping I can keep the mildew at least controlled until the end.

Trichomes are what matter for determining harvest time. Pistils help, but trichs are what matter. :grinning:

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I’ve got a microscope to monitor them as well!

Caution !!! never use vinegar it will kill you plant in 1 day I’ve used it to kill weeds

Used peroxide. WIll have to wait and see how effective it was against the mildew, but it definitely browned some pistils and I’m all set with putting anything else on the plants. If needs be I’ll harvest early - I’d guess I’d get at least a pound out of them right now, I don’t need much for myself, and I mostly grew it for shits and giggles anyway.

U can use vinegar but it strips natural waxes off cannabis leaves leaving it more susceptible in the. Future baking soda to me seems the most intrusive…most possible I’ll effects for sure peroxide is harmless and actually kills mold spores you know how bleach removes mold it still dosent kill the spores peroxide does

Keeping your rh under control will help keep it in check too.

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