Treating powdery mildew on CannabisPosted by On

pm-leavesTreating powdery mildew on your marijuana plants is incredibly difficult. Powdery mildew is caused by a variety of fungi resulting in the appearance of a white or gray growth patches on the leaves of your plants. This fungi will cripple photosynthesis and your plants will become weak and eventually die.

What Causes it?

The best course of action is to take preventive measures to avoid powdery mildew on your marijuana plants in the first place, to know how to prevent it we must know what causes it.

Poor air circulation – Be sure to keep your plants evenly spaced apart. Over crowding creates a thriving environment for powdery mildew spores. Be sure to have a proper ventilation system setup allowing for fresh air to be drawn into your grow area. Include some oscillating fans to help move air around, It will also help strengthen your plants creating thick strong stems.

High Humidity – Powdery mildew thrives in humid environments.  Controlling your humidity and keeping them at proper levels will help prevent the growth of powdery mildew on your cannabis plants. Vegetating plants require higher humidity 60 -70% but when your marijuana plants begin to flower, you slowly need to reduce the humidity level keeping it as close to 40% as you can.  Be sure to water your plants when they will receive at least 5 hours of light before lights off.

Poor air quality – Having good air flow is essential but the powdery mildew spores become airborne real easily being spread by your fans. Be sure to clean your grow area thoroughly after each harvest to promote clean growing conditions and invest in a air purification system. A air purification system will help neutralize any airborne spores.


  powdery-mildew-on-marijuana-plants-36486-w800Sometimes no matter how many preventative measures you take powdery mildew will still rear its head around the corner and spring out of nowhere. When this happens catching it early is key. First thing you will want to do is very carefully remove any infected leaves and place them into a plastic baggy and seal it air tight. You should be careful when doing this not to jostle the spores and send them airborne. You can also take a wet paper towel to carefully clean any infected areas that are small and the wet paper towel will help keep the spores from flying into the air.

Next thoroughly clean your grow area with bleach water. If growing in a tent wipe all surfaces from top to bottom. Change all your air filters/vents and clean your fans.

Now you will want to treat your plants to prevent any new or further growth. Like anything on the internet your sure to find a million different recipes / mixes that people swear works better than anything else for treating powdery mildew on your cannabis or any other plant at that matter.  So I will focus on a couple mixes to spray on your plants that I have personally tried and have found success with that are all natural and chemical free.

  • Milk – 40% milk – 60% water in a spray bottle apply to your plants. The milks protein will create a natural antiseptic under the grow lights thus eliminating the mildew spores and growth. This should be applied  shortly after the lights switch on.
  • Vinegar – I have found that a couple teaspoons of apple cider vinegar mixed with a quart of water will help reduce and remove any mildew growth. Using a spray bottle apply to affected areas.
  • PM Wash – By NPK Industries is ionized water than when applied will prevent any new mold growth to the areas treated. I found that this is best applied before growth is ever even noticed as a preventive measure. Its safe to use on all stages of growth.

These are just a couple methods. Do a quick Google search and you will find many more home remedies for controlling powdery mildew on your marijuana plants. You can also always hit up you local grow store and go nuclear but when using on your cannabis plants that you will eventually consume its best to go all natural and organic.

You need to be sure to identify the cause of your powdery mildew growth otherwise you will find yourself in a nonstop battle that will get out of hand quickly. Once identified you will be able to prevent any future outbreaks and grow clean quality medication.








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