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Powdery mildew, also known as white powdery mildew, comes from lots of different fungi. Powdery mildew looks like white or gray powdery growths on your marijuana plants’ leaves.

It appears on grow areas indoors and outdoors and is foreshadowed by small bumps on the topsides of leaves. Typical species of fungi that go after hops will also go after your marijuana plants.

What is Powdery Mildew

Powdery mildew spores can be transported to your plants on the wind, through air ventilation systems, from pets, and any other living thing that moves (including yourself). Until the surrounding environment is ideal, the spores from mildew will stay dormant, biding their time.

What is powdery mildew cannabis
Powdery mildew on cannabis leaf

This is why powdery mildew can be so tricky – you never know when it is lurking and waiting for the perfect time to strike. Powdery mildew is one of those conditions that is better to prevent from the get-go.

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The main problem arises with powdery mildew when it is able to grow until it severely slows down photosynthesis and, therefore, ruins your harvest. It, therefore, needs to be taken care of as soon as you are able to identify it. Powdery mildew is not as uncommon as some other conditions, so it is something that you need to keep an eye out for.

Signs of Powdery Mildew

You will know you have powdery mildew when you notice fuzzy, flour-like circular patches on your marijuana plants’ leaves. You might see leaves that look spotted, mottled, and wilting. The powdery mildew infection will quickly spread to surrounding leaves and will “eat” everything in its path.

Powdery mildew is quite recognizable, given its stark white in contrast with the green leaves, and it can be removed if you use proper treatment in a timely manner. The problem with powdery mildew is the spores – often you can’t even see them as they are spreading throughout the air, making them extremely difficult to avoid and combat.

Signs of powdery mildew weed
Signs of powdery mildew weed

Powdery mildew is the most likely to occur when humidity levels are high (above 55%) when there is not much air ventilation happening in your grow area. It also occurs when there is overcrowding of your marijuana plants at the grow site or in the grow room. Leaves touching other leaves are more likely to spread powdery mildew to each other, making it even harder to eradicate when your setup looks like that.

Powdery mildew generally goes for the youngest plants first, spreading across the entire plant and ruining the stems, buds, and leaves of your plant. You will notice a damp sort of smell coming from your buds – this is how you will know which buds have been affected by the powdery mildew.

Once the fungus has invaded a bud, it cannot be taken away. If the powdery fungus continues its course of action, it will eventually make your marijuana plant turn yellow, which will become brown, and then the plant will simply die.

It is crucial that you never let your plants reach this point. Make sure you are constantly inspecting your plants and always keeping a close eye out for any unexpected changes in your plants.

Not sure if your marijuana plants suffer from a powdery mildew infection? Check the article Marijuana diseases for a list with pictures of all possible marijuana diseases

How To Get Rid Of Powdery Mildew

There are some tricks to get rid of this irritating nuisance. But the best way will always be…

Avoiding Powdery Mildew

If it’s possible, you should take certain steps to avoid an invasion of powdery mildew anyway. When you initially plant or transplant your plants into their mature location, make sure they have plenty of extra room. If they are planted closely together, the likelihood of powdery mildew popping up is significantly higher.

When you water your marijuana plants, you should make sure that you are doing it at a time of day when they will receive five hours or more of light after that. This can be artificial or natural light, depending on your growing situation.

You can also try using a UVC light if you are an indoor marijuana grower, which will keep any missed powdery mildew spores from going for your valuable plants. Some growers who have a few years’ experience under their belts might prune some of the fan leaves that don’t receive any direct light due to shading.

UV lights
UV lights

This makes it so there are less ideal spots for powdery mildew to land and begin growing. It also has the added benefit of your plant conserving its energy and using it more efficiently for other leaves and growths.

Treating Powdery Mildew

If it’s possible, you should take certain steps to avoid an invasion of powdery mildew anyway. When you initially plant or transplant your plants into their mature location, make sure they have plenty of extra room. If they are planted closely together, the likelihood of powdery mildew popping up is significantly higher.

It can also be used preventatively before any powdery mildew arises at all. Another option is to do the same thing with one-half teaspoon of baking soda mixed with a quart of water.

Ingredients to create your own Powdery Mildew spray
Ingredients to create your own Powdery Mildew spray

Other options for destroying or preventing the powdery mildew include oil sprays such as neem oil, sesame oil, or fish oil. These sprays can also work well for other fungal diseases. A final option at your disposal is a milk spray made from 40% milk and 60% water.

This works so well because the milk has protein in it which reacts to the sun and naturally forms an antiseptic. This antiseptic is what kills the mildew. You can use a milk spray preventatively by spraying it on your plants every ten days, but only when the sun (or artificial light) is shining brightly. This is a common method for all gardeners to use on their plants.

Milk & Water spray to threat Powdery Mildew
Milk & Water spray to threat Powdery Mildew

In order to take care of a plant that has been infected with powdery mildew, you should utilize a plastic bag to remove the leaves that have been affected. Seal the bag and then put it into a disposal container that has a tight lid.

The reason for using the plastic bag is to prevent the spores from being sprung into the air and infecting other plants nearby. After removal of the infected areas, treat your plant with fungicide on the stems that held the removed leaves.

‘Plants are infected for weeks before they show the first symptoms.’
~ Jorge Cervantes

Other Methods
There are a few alternative methods that you can use to heal your plants, including oil sprays such as cinnamon oil, garlic oil, coriander oil, clove oil, jojoba oil, or cottonseed oil sprays. A commercial product like Mold Control will always to the job. If you want to make sure to get rid of powdery mildew, buy something like Bergman’s Plant Protector.

marijuana plant protector
Protect Your Plants From Mold With Plant Protector

There are also copper-based applications that you can purchase at any garden center. You can also try one tablespoon of hydrogen peroxide mixed in with water, which destroys the fungus by oxidizing its cell walls. Yet another solution is one teaspoon of limonene that is combined with one quart of water, offering fungicidal properties without actually killing the fungus altogether.

Finally, there are sulfur burners to control and contain the fungus. When using sulfur burners, make sure that you keep away from it when the treatment is taking place – in people, sulfur burners can cause respiratory inflammation. After the treatment, be sure to wipe off every window and wall completely so that you know any residue from the sulfur burner has been removed.

Powdery Mildew Plant Symptoms

Leaf Color

  • Pale colors
  • White patches on leaves

Leaf Symptoms

  • Upper leaves and newer growths are affected
  • Lower leaves and older growths are affected
  • Visible white powdery patches on the leaves
  • Spots
  • Mottled, mosaic on leaves
  • Wilting and drooping of leaves

Plant Symptoms

  • Mold

If you are looking for an extremely simple way to get rid of the powdery mildew, you should give the tap water – paper towel method a try. Simply get the paper towels wet and gently wipe your infected leaves with them, therefore removing the mildew that is already there. When doing this, make sure you don’t bump your leaves too much, as that could cause spores to enter the air and spread.

remove Powdery mildew with paper towel
Remove Powdery Mildew with a paper towel

You can also incorporate at least two fans into your grow room to improve the conditions and lessen the chances of powdery mildew development. You should have one fan directing air through the leaves of your plants and the other fan facing out from your grow room. This is so the “used” warm air is dispelled from the room and replaced with fresh air.

Powdery mildew destroyed your grow? Get new seeds from my seed bank

Remember that plants with strong genetics have less chance of getting sick and are less vulnerable to pests and diseases. So make sure to buy cannabis seeds from a trusted seed bank.

Thanks for reading. Please leave comments or questions below and don’t forget to download my free grow bible.

Happy growing!

Robert

The founder of I Love Growing Marijuana, Robert Bergman, is a marijuana growing expert that enjoys sharing his knowledge with the world. He combines years of experience, ranging from small-scale grows to massive operations, with a passion for growing. His articles include tutorials on growing... [read more]

76 Comments

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  1. By Mike Giannini

    ,25 Jan 2013
    Can I smoke buds that had white mold on leafs? Thak You
    1. By Benny

      ,22 Jan 2019
      Not wise to smoke pores.. Even if dried.. I wouldnt .
  2. By jamison crevier

    ,19 Sep 2013
    iam trying applecider vinegar on my babys. white powdery mold starting on leaves. I really hope this works.
    1. By Deborah preciado

      ,14 Sep 2017
      I just seen three leaves affected after humid rain and sprayed with apple cider
    2. By Nanna

      ,15 Sep 2017
      Gonna try the apple cider vinegar mix, should this be done when lights are on or will it burn them? helping a friend, so don't want to piss him off by burning his baby's.
      1. By latewood_ILGM

        ,20 Sep 2017
        Nanna, You are talking about spraying an acidic solution on the plants; I think during lights out would be best. You also need to fix the issue that allowed mold/mildew to develop in the 1st place. OK? Good Luck, lw
        1. By Nanna

          ,26 Sep 2017
          Ty, xxx's very much ! did that it's gone ! Thank's again !
          1. By juwn

            ,13 Oct 2017
            hey did it actually work? because i am out of option :(
  3. By George

    ,12 Jan 2014
    I just want to say...Thank you for this Info, and your help :)
  4. By Jett Thompson

    ,24 Nov 2014
    Can I smoke buds that had power mildew. I've taken off fan leaves and sprayed plant with clear water,I'm flushing the plant to harvest them. Thanks Jett
    1. By Larrie

      ,06 May 2017
      You could get very sick from smoking mold in your buds. It doesn't go away with drying, it is compressed tight inside your buds. People with respitory issues or even a healthy person can be affected. When you smoke moldy […]Read More
  5. By freeman

    ,06 Feb 2015
    What is the scientific name for the Powdery Mildew I have someone that had an attack from the mold needs to know. Thank you ƒg
  6. By josi

    ,21 Apr 2015
    powdery mildew can be controlled by Cleanlight!!!!
  7. By N

    ,02 May 2015
    powdery mildew specifically does not contain or release harmful mycotoxins found in most mold/fungi species. In short, although disgusting to the palate and may cause a vomit reaction If smoked, powdery mildew unlike other molds, is safe. Don't take my […]Read More
  8. By Kyle Sacker

    ,24 Jun 2015
    to always give myself the best chances of not getting powdery mildew I clean my whole grow room with this stuff called Grow Clean. had PM once before this stuff!! introduced grow clean and bam! never saw it again
  9. By Bill Graves

    ,24 Jul 2015
    One thing that worked for me in a greenhouse with squash plants is one tablespoon of baking soda in a gallon of water. For more extensive treatment try using potassium bicarbonate as potassium is a plant nutrient and does not […]Read More
    1. By latewood

      ,24 Sep 2015
      I too use this method of Baking Soda to combat Powdery Mildew, mold. Baking Soda is highly alkaline. Mildew cannot thrive in such an alkaline environment. A friend of mine in the Carolina's likes to spray diluted milk to combat […]Read More
  10. By Symptom Checker – Identify Marijuana Plant Problems

    ,24 Jul 2015
    […] Powdery mildew […]
  11. By Diseases on Marijuana Plants, and How to Treat Them

    ,29 Aug 2015
    […] You can recognize powdery mildew by its white color. It will cover the foliage of the plant and inhibit the photosynthesis process. If your plants suffer from powdery mildew, there are a number of safe naturally based sprays you […]Read More
  12. By kim

    ,22 Sep 2015
    How often can i spray my plants with the Vinegar water/
    1. By latewood

      ,24 Sep 2015
      Can I ask why? I would be wary of spraying vinegar water on my plants because, that is acidic, and could harm the plant if not done with the utmost of care. Please join our ILGM Support Forum for more […]Read More
      1. By Housewife Grower

        ,20 Apr 2016
        ACV and Milk combo. 2tbls ACV and 1/4 cup of milk to one gallon tap water in Co. Basement grow. Sprayed with 5 hours of light as recommended for use with milk. I had bad PM covering 70% of 4week […]Read More
        1. By Jennifer ILGM

          ,20 Apr 2016
          Thanks for sharing Housewife Grower
          1. By deadleg

            ,18 May 2018
            Apple Cider Vinegar
          2. By thor

            ,30 Sep 2018
            apple cider vinager
        2. By Jimmy pot seed

          ,28 Aug 2016
          Awsome info,hope it will do the same on out door grow
        3. By weedsky

          ,27 Dec 2016
          It had no affect on the taste either I am in week 6 flower totally devastated it's my 1st grow hoping I can wipe and clean
        4. By VF

          ,11 Sep 2017
          how often do you treat with this method?
          1. By Stacy ILGM

            ,11 Sep 2017
            Hi VF, We discuss several methods in this article, to which method exactly are you referring?
        5. By Sue

          ,20 Jul 2018
          Hi Housewife Grower. Did this work? When you say 5 hours. Is that after the lights have been on for 5 hours or when they have 5 hours to go before they turn off? Thanks in advance!
  13. By Cecilia

    ,24 Sep 2015
    I used some garlic water early on and hit the PM right away at first tiny sign on my outdoor. Now...they are budding beautifully, and I noticed one tiny spot today. Is it ok to use the ACV or Garlic […]Read More
    1. By latewood

      ,24 Sep 2015
      This is one of those judgement calls. You are the best one to make this decision. You are there, and used this solution already. As with anything added, especially home type remedies; One must exercise good judgement and caution. Feel […]Read More
  14. By Newbie grower..

    ,09 Oct 2015
    Great site! I don't really smoke the stuff but have enjoyed growing it a few times. I live in a small coastal town so fog has always been my enemy, and the dreaded nasty caterpillars!! UGG Since we no longer […]Read More
    1. By Jennifer ILGM

      ,12 Oct 2015
      Thanks for sharing Newbie grower!
  15. By Stop Bud Rot On Marijuana Plants Now!

    ,01 Dec 2015
    […] might have cracks that mold could travel through. Any damage caused by caterpillars, snails, worms, mildew, or other pests can also create a “tunnel” of sorts for gray mold to get inside your […]
  16. By Stop Diseases On Marijuana Plants Now!

    ,18 Feb 2016
    […] You can recognize powdery mildew by its white color. It will cover the foliage of the plant and inhibit the photosynthesis process. If your plants suffer from powdery mildew, there are a number of safe naturally based sprays you […]Read More
  17. By Bacterial And Fungal Controls

    ,24 Mar 2016
    […] Quisqualis These are naturally occurring hyperparasites of powdery mildew. They form colonies on the infection, reducing growth and may eventually kill powdery mildew on […]
  18. By dale

    ,19 May 2016
    I have been using a product called CU H2O this is been working real well for me better than anything else that I've tried it is a natural product and that's what I like about it.6 month now greater looking […]Read More
    1. By Dale

      ,04 Oct 2016
      I left a post here a couple months back about powdery mildew and I found a product called CU H2O I have been using this as a preventative and for the first time in 6 years ago and I have […]Read More
      1. By Jeannie

        ,30 Sep 2019
        Hi ,where did you purchase this product?
  19. By Jay

    ,12 Jul 2016
    Hi, we have had a lot of success with the DragonJuice PM2 from Completely Organic. It's an organic, non-gmo, toxic plant extract blend and PM fall off immediately and no toxicity to plant or quality of bud. In fact, gets […]Read More
  20. By John H Carlson

    ,14 Aug 2016
    I have never gone pot for myself or commercially but have serviced many growers. With the issue of air born mold spores/and or mycotoxins I have developed an air scrubber with the ability to turn 660 cfm of purified air. […]Read More
  21. By Swampy

    ,26 Sep 2016
    I've been growing for over 35 years. It's basically farming and you learn something new each and every year. The tips you have here are sensible and easily understood. Nobody knows it all and your guide sure helps...thanx.
  22. By Green Crack Strain Review – I Love Growing Marijuana

    ,23 Jan 2017
    […] grown outdoors, however, it has the ability to stretch a bit more. Because it can be sensitive to powdery mildew, it is recommended to keep the humidity low when growing Green Crack. Ideally, when grown outdoors, […]
  23. By cory

    ,16 Aug 2017
    IN MY OPINION THE MILK AND WATER DOESNT WORK iv did this last year and it went away for a couple days but came right back quick...but the slufer burners work awsome and so does the organic apple cider vinegar […]Read More
    1. By latewood_ILGM

      ,20 Sep 2017
      Milk curtails the growth of the spores, and must be reapplied every few days as you proved here. You cannot just treat an issue once and hope that is all you need to do. This type issue requires diligence. I […]Read More
  24. By Jim Heron

    ,30 Aug 2017
    ACTINOVATE !!! It's all I use for mold, and fungus issues ! Root drench every 10 days, foliar spray once a week. It will control existing mold, but prevents it completely if used before flowering ever starts. Pricey, but nothing […]Read More
    1. By latewood_ILGM

      ,20 Sep 2017
      Thanks Jim :D I will have to check and see how safe this product is to use.
  25. By Nancy

    ,30 Sep 2017
    After apple cider spray do the plants need to be washed and how long til they can be harvested.
  26. By Doug

    ,29 Nov 2017
    We had limited success with sprays and home remedies at best. Nothing seems to really work so great. We found a place to buy a couple of UVC lights and tried it on a small section of our grow. It […]Read More
  27. By latewood_ILGM

    ,07 Dec 2017
    1doug, Yes, UVC lights are known to a lot of growers, especialyl growers that are always adapting to newer ideas and products.
  28. By Trent Thiel

    ,19 Dec 2017
    This is no different than what is seen on grapes and wheat. Powdery mildew is most prevalent on lower leaves but can cause blighting of the upper leaves, heads and awns of susceptible cultivars. Within a few days after they […]Read More
    1. By Trent Thiel

      ,19 Dec 2017
      May have been obvious, but I should have clarified that a recirculated air filter solution is for indoor growing only.
  29. By lorene miller

    ,13 Jun 2018
    How often do you spray, using apple finger and water?
    1. By latewood_ILGM

      ,15 Jun 2018
      In general indoors or in greenhouse we treat plants once every week or 2 to be proactive
  30. By michael

    ,20 Jun 2018
    hi guys first time growing in a small hoop house .10 x 16 with only 6 plants.2 fans on the plants. just notice what i think is powdery mildew. how often do i spray with the ACV ? my girls […]Read More
    1. By latewood_ILGM

      ,21 Jun 2018
      michael, ACV? I suggest following the directions when using any product.
  31. By Rita

    ,31 Jul 2018
    First of all thanks for helping us out, I'm in my 6th week of indoor grow and now this pops up! Will my foliar spraying the leaves and buds with the vinegar solution take away from my final product this […]Read More
    1. By Benny

      ,22 Jan 2019
      Thats my issue aswell .im in my 4th week flowering..mildew isnt bad..few spotts
  32. By grobi43

    ,19 Sep 2018
    Just completed a outdoor grow with-mixed results, trending toward failure - Bud Rot due to a span of heavy rains, high heat and humidity, resulted in loss of half of plants. Salvaged what I could; noticed the bud is fluffy, […]Read More
  33. By Benny

    ,22 Jan 2019
    Can i spray the milk&water mixture on my buds?? 4th week into flowering
    1. By latewood

      ,13 Feb 2019
      Benny, that would be what I call "touch and go"... When spraying anything on buds late in flower it is possible to create mold or a rot issue. Best I can say is; It is not worth anything with powdery […]Read More
  34. By Charlie

    ,10 Feb 2019
    Hello there i am in Last two weeks of my plants and i got this problem with powdery mildew and its spearding around fast what is quick action for it to fix it without harming my buds plz help and […]Read More
    1. By latewood

      ,13 Feb 2019
      Charlie, I suggest you go to our forum for the fastest support and ability to discuss your situation and what may have caused you issue. Go here: support.ilovegrowingmarijuana.com. See you there :)
  35. By Ron

    ,25 May 2019
    I wouldn't spray milk on your buds. Milk is too perfect of a medium for molds to thrive in. There are some safe and effective products out there that can eliminate your PM and keep your other pathogens at bay. […]Read More
  36. By Robin Gold

    ,19 Jul 2019
    Thank You for all if the Informattion on powdery mildew. Im growing with someone else in a greenhouse and she doesn't have the humidity under control at all. And though she just planted her Plants 2 weeks ago they are […]Read More
  37. By Car

    ,04 Aug 2019
    How often should you spray the leaves that have powdery mildew
  38. By latewood ILGM

    ,05 Aug 2019
    Car, I Suggest You Go Here: Support.Ilovegrowingmarijuana.Com Our Members And Staff Can Help Give You Informed Advice. We Have A Lot Of Topics That You Can Research.
  39. By Lilli

    ,14 Aug 2019
    Can I Treat white powdery mildew with peroxide when in flowering stage?
  40. By Dan

    ,26 Sep 2019
    I seem to have powdery mildo on only one plant in my garden. It was a different strain, and added weeks after the rest of my plants. Can I treat this single plant . And let it keep going? Or […]Read More
  41. By Ron

    ,28 Sep 2019
    Milk doesn't work. Bicarbonate products can work, but can be hard on foliage if used to frequently. Vinegar is hard on leaves too. You'll find recipes for using it as an herbicide all over the internet. It is not an […]Read More
  42. By Chris

    ,01 Oct 2019
    Love all the useful tips! Thanks for keeping it real!

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