Stop Powdery Mildew On Marijuana Plants Now!

Page content

Powdery Mildew On Marijuana Plants

Powdery Mildew On Marijuana Plants

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

What is powdery mildew cannabis

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.

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.

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

Signs of powdery mildew weed

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.

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.

Download my free marijuana grow guide at this link for more growing tips

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

Get rid powdery mildew cannabis

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.

Download my free marijuana grow guide at this link for more growing tips

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.

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.

If you do end up having a powdery mildew problem, one way to solve the problem is at home. One home remedy is 2 teaspoons of organic apple cider vinegar mixed with one quart of water. Mist this mixture onto your plants to both kill the powdery mildew growth and prevent any more from cropping up. 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.

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.

Download my free marijuana grow guide at this link for more growing tips

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.

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.

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 Marijuana Mold Control.

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.

Marijuana 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.

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.

Remember that plants with strong genetics have less change of getting sick and are less vulnerable for 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



Download the Ultimate Grow Guide for FREE!
Learn the basics of growing marijuana and get started today
  • How to get the biggest yields from cannabis plants
  • What you need to get started, without wasting money
  • The most common mistakes you do not have to make
We guarantee 100% privacy.

Comment Section

20 thoughts on “Powdery Mildew On Marijuana Plants

By Mike Giannini on 25 January 2013 at 02:22

Can I smoke buds that had white mold on leafs? Thak You

By jamison crevier on 19 September 2013 at 02:56

iam trying applecider vinegar on my babys. white powdery mold starting on leaves. I really hope this works.

By George on 12 January 2014 at 17:06

I just want to say…Thank you for this Info, and your help :)

By Jett Thompson on 24 November 2014 at 16:55

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

By freeman on 6 February 2015 at 18:10

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

By josi on 21 April 2015 at 17:47

powdery mildew can be controlled by Cleanlight!!!!

By N on 2 May 2015 at 05:39

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 word for it tho, at very least google what I said and confirm it. Prevention is the best cure. never vend pm covered meds., ever.

By Jennifer ILGM on 4 May 2015 at 09:03

Thanks for sharing!!

By Kyle Sacker on 24 June 2015 at 17:31

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

By Bill Graves on 24 July 2015 at 01:31

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 have sodium in it. Sodium bicarbonate works because most fungi do not like an alkaline environment and the bicarbonate is just alkaline enough to inhibit the fungus.
Wish you luck.
Bill Graves
Agricultural and Horticultural Consultant
Homestead, Fl

By Jennifer ILGM on 27 July 2015 at 10:39

Thanks for the tip Bill.

By latewood on 24 September 2015 at 08:01

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 mildew; I tis gentler than Baking Soda; IN his opinion.

By kim on 22 September 2015 at 17:19

How often can i spray my plants with the Vinegar water/

By latewood on 24 September 2015 at 08:05

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 opinions and expert advice. :)

By Cecilia on 24 September 2015 at 02:27

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 water while it’s budding w/o affecting the buds?

Thank you!

By latewood on 24 September 2015 at 08:11

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 free to join our support forum. We have many growers from around the world will to help you grow successfully.

By Newbie grower.. on 9 October 2015 at 22:10

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 have an ozone layer to protect us, our summers have been much warmer. 3 girls did Fantastic! I picked bugs, never sprayed even though there are (Safe Caterpillar Killers I have read about. One plant finished beautifully but my last 2 Fab girls broke out with mildew even with ideal hot outdoor conditions. First I used a wet paper towel and wiped off what I could and pinched off where it was easy with latex gloves being careful not to spread spores. Then I used this sites recommended 2 tsp of Apple Cider Vinegar in a quart spray bottle. I sprayed only affected areas 2 hours before the sun went down last night. This morning 2 hours before the sun started blaring I sprayed the leaves and buds (only 1-2 weeks to finish line) and presto, magic, it is all gone! Timing was good. I don’t think you should spray right before dark as bud rot may occur but this simple organic vinegar and water did the job! Good luck and thanks for this info, it was perfecto!

By Jennifer ILGM on 12 October 2015 at 11:52

Thanks for sharing Newbie grower!

Leave a Reply