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Grower Tip of the Week – How to Get Rid of Powdery Mildew


This week I asked my Facebook friends: “What is the best way to get rid of powdery mildew?”

Here are the answers I received. Like always, these are not MY tips, they are from my survey, so take them with a grain of salt:

How to Get Rid of Powdery Mildew on Your Marijuana Plant:

  1. “Sulfur burner works best for powdery mildew.” – Sarge Hart
  2. “Powdery mildew is a common fungus, can be prevented with good ventilation and low humidity levels. Try a fungicide clean and cut infected area it thrives on the plants nutrients.” – Alexander Cosey
  3. “1 tsp. of baking soda in one gal. of water sprayed on plants until problem disappears. Doing it right now and is working well!” – Tammy Freire
  4. “Try a sulphur spray or burner.” – Josue Lopez
  5. “Stop mildew before it starts. Cleanliness – avoid humidity – stale air – and low light. Get some air moving around the plants. Avoid excess nitro. Copper and sulfur spray can help prevent. Biological apply serenade or spray with baking soda and water. Baking soda changes the ph and mold cannot grow.” – Ken Hochhalter

Want more grower’s tips? Check out our other articles on growing marijuana!


About Author

Johnny Green


  1. This is Gülşah from Turkey/İstanbul

    sulphur supplier in bulk or in bigbags.

    Turkish and Grek sulphur powder/granular for sulphur burners.

  2. hi, so i need some help! my bf was given a couple plants to take care of and he did his best without the proper equipment or knowledge really..so but we are now at the point where they need to be cut to dry but there’s mold. are they salvageable at this point or do we just get rid of them? its mainly just got mold on the stocks a few buds do have some… i am completely sorry if i am not usuing the right terminology. i am under education in this department for sure! please any advise would be very much appreciated “).

  3. This is all good info, but also you want to avoid over-planting an area (if it’s too close there isn’t enough air circulation, which fosters mildew, and if it’s too dark, it also fosters mildew growth), and avoid using nitrogen-rich fertilizers toward the end of summer. Here is a good article on it: http://www.kelp4less.com/powdery-mildew-how-do-i-get-rid-of-it/. And you can also use MKP as a suppressant (no nitrogen content) – http://www.kelp4less.com/shop/monokp/

  4. But when flowering I would go with neem oil because it is organic. But keep humidity low as possible and spray your plants and let the humidity drop again before you spray again. You should never foliar spray plants with the lights on, but this is where you would like the lights on to dry the plants up….Plenty of air flow is a must.

  5. luckily I dont have money to waste!

    man I only got 1 eye!

    Yes sulphur is burnin only at night!

    I need a de-humidifier . I borrowed 1 from a neighbor

    and I remove 10 gallons of water from the air! wow

  6. I wouldn’t advise using one. It didn’t come with any protective goggles, and i had a hard time finding info online about which goggles to order that would protect from uv-c rays. The goggles I bought, which I thought were properly rated, were not, and I did some serious damage to my eyes. I had headaches and irritation for a week afterwards. The effects are similar to welding flash, or getting sunburned eyes. My eyes were extremely sensitive to the sun and indoor light sources for weeks afterward, I have to wear sunglasses around any bright light source to avoid headaches now. Unless you are 100% sure that the eye protection you have is rated for uv-c light do not use one of these wands or any uv light technology. Also, the unit I bought had a safety shut off feature that prevented the unit from working if it was held in any position other than pointing directly downward. This made it really impractical because I had to bend the stalks over to ensure exposure on lower branches. I have since switched to using a sulphur burner, and it has almost entirely eraticated the mildew.
    For my unit I just fill the unit 1/3 full of sulphur and plug it in. I leave the room and tape up the door, leaving it to burn for an hour or so. When you go back in to unplug the unit, you’ll want to wear a respirator, or hold your breath if you can get in and out quickly. Give the room a few hours before you go back in, to let the sulphur to settle from the air. The properties of the sulphur are airborne so it gets into all the cracks and crevices and hard to clean places in your room where the spores are. I usually do this right before switching over to flower, and any time the room is being cleaned out. I’m assuming that if you run it during the flower cycle it might adhere to the sticky buds and leave a taste. Doing it late in the veg cycle doesn’t leave any taste. This combined with a baking soda spot treatment for flare ups seems to be keeping my problem under control. Whatever you do don’t use uv-c without 100% guaranteed properly rated eye protection. The wand seemed to work , but in my opinion isn’t worth the risk.

  7. I saw that too!

    dont even call that medical! those spores will make you itch!

    skin rashes!

    Im glad he took those vids down! nasty

    everything else he says is great , balance air , water temps, nutrients

    I had his little book 30 years ago!

  8. Sulphur will work, but Its very hard to rinse off of the leaves and if used during flowering it sticks to the buds, making the end product taste of Sulphur. I fill a spray bottle with water and add 1ml scoop of baking soda, and 5 ml of olive oil for use in my veg room. The soda changes the ph making it hard for mildew to thrive, and the oil acts like a coating agent which works like a thin barrier. For my flower room I use a similar mixture, only without the oil, and half the amount of soda, I found that the oil when used during the flower cycle slowed the bud development and affected the taste. The only problem is that the mildew is nearly impossible to completely eradicate, you can keep cleaning and treating the plants, but the spores have been blown all around the room by fans etc… even after repeat treatments, and complete bleach down sterilizations of the room I still get outbreaks from time to time… i find trimming the lower leaves and increasing air circulation under the canopy helps keep it from developing. Also I just bought a UV-C Ultraviolet sanitizing wand


    You need to wear uv-c rated protective goggles to protect your eyes, and long sleeves etc to avoid skin contact. Its the same technology found in water and air purification systems, basically it kills 99% of bacteria, microorganisms, germs, etc and even insect larvae. From what I have read it has no detrimental effect on the end product. I plan to expose my finished dried product to the light to kill any of the remaining spores… cause personally I don’t want spores in my lungs. I can’t vouch for the effects of the light personally yet, but plan to test it this week and report back.

  9. I watch a Hodge Cervantes. Video using a bath of hydrogen peroxide at 3% it was made into a batty with water and the full budding branches were rinsed an lightly stirred gently rinsed off and a fan put on them. It was awesome and I saw it last month on weed bloc and now I can’t find it.

  10. I am having a problem with powdery mold on my patients plants. I have heard about burning sulfur to cure the PM however I am unsure of where to locate it a small amount. Can anyone help me with this?

  11. I recently battled powdery mildew on plants 7-8 weeks in flower.

    The best solution I have found is to spray down the plant with the following:
    1/4 cup hydrogen peroxide 3% or better
    1 tspn Dawn diswashing soap
    1 gallon of water

    I had to spray them a few times over a few days but it cleaned off the mildew enough to harvest the plant and suffer no taste or powder issues.

    The powdery mildew did screw up weeks 7,8, 9, 10 on a seventy five day flowering strain. The crystal production has been greatly reduces.

  12. Tammy Freire — 1 tsp. of baking soda in one gal. of water sprayed on plants until problem disappears. Doing it right now and is working well!

    is tammy spraying it when the lighs are shut off or on?

  13. Ive heard of dilluting milk in water

    spraying plants.

    overcrowding and excessive fan leaves can stop air flow and cause pm

    spacing plants out helps indoors
    never had problems outdoors with PM

  14. thats funny , 1 time a friend came over rolled a joint off the table

    he was smokin a bud with red and white hairs

    i have a red and white dog . do the math

    lesson : dont grab buds that aint yours!

  15. Without powdery mildew, how will 12th graders rip off 9th graders with shitty weed? “Look at all those crystals…you’re lucky I’m not charging you a dub 5…”

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