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Powdery mildew is extremely common for both indoor and outdoor cannabis growers. It is a fungal disease that spreads in on spores on people’s clothing, pets, through the air, or on cuttings from other plants. Spores can seem like they are gone, but in fact they are often lying dormant and waiting for the conditions to get back to their optimal range.

Powdery mildew is most common in areas with moderate temperature, high humidity, and low light intensity. It often attacks young cannabis plants that are only a few weeks old. Powdery mildew will spread to all parts of the plant, including stems, buds, leaves, and stalks.

Powdery mildew hinders photosynthesis and cripples the harvest.  The first signs of powdery mildew are raised surfaces on the top of the leaves. The plants will appear as if they have flour or sugar on them. If left to spread, powdery mildew will cause the plants leaves to yellow and then turn brown, and die. If the mildew gets on the buds it cannot be removed. The buds need to be thrown out.

How To Prevent and Control Powdery Mildew on Cannabis

  • If you see plants with powdery mildew, separate them from the other plants so they can’t spread their disease to the other plants.
  •  Leave enough room between the plants so the plants can breathe.
  •  Water the plants at a time of day where they will receive 4 to 5 hours of light afterwards so they have time to dry before the dark.
  •  Keep the humidity below 50% in the grow room.
  •  Place a bag over the infected leaves and remove the leaves and throw them away. The bag can help keep the spores from spreading in the room.

Use Any of the Following Products to Safely Get Rid of Powdery Mildew on Cannabis

  • Neem oil
  • Garlic
  • Milk
  • pH up (if you are in need of pH up we recommend using the General Hydroponics brand)
  • Sesame oil
  • Hydrogen Peroxide added to water (I tablespoon per gallon)
  • Cottonseed oil spray

To learn how to grow cannabis indoors and how to grow massive healthy cannabis plants outdoor, make sure to enroll at Cannabis Training University.

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Luis Cordova
Luis Cordova

Luis Cordova is a distinguished author, and renowned expert in cannabis cultivation, who possesses a Master's degree in Plant Biotechnology and Pharmaceutical Science. As a valued contributor to highly esteemed publications such as Cannabis Training University and Maximum Yield Magazine, Luis has emerged as a trusted source of guidance and knowledge in the cannabis industry. Having written thousands of informative articles, Luis is widely recognized for his comprehensive expertise on cultivating cannabis, both indoors and outdoors.

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