Powdery Mildew



Powdery Mildew

Powdery Mildew by Jeff Kubina

Powdery mildew (Blumeria graminis) is a fungal disease that is common to indoor plants, especially during fall when temperatures begin to drop. Powdery mildew prefers temperatures between 60-70 ºF and humidity exceeding 40%. Pay close attention to your grow room environment during the night since this is when these conditions become most favorable.


The stems and leaves of infected plants show white powdery patches. As the fungus matures, the white spores will turn brown. Leaves will eventually yellow, brown then die.

Powdery mildew can affect fruits and flowers as well.


Prevention is not only better than the cure, its alot easier. Use these tips to minimize your risk of infection:

  1. Bring temperature above 75 ºF and lower humidity below 40%.
  2. Choose plant genetics that are resistant to the disease.
  3. Increase air flow by adding fans and separating plants.
  4. Water during the morning to give your plants time to dry.



Start by quarantining infected plants so that the disease does not spread. Remove badly infected leaves, this helps to increase airflow around the plant. If pruning with shears, disinfect after each cut with a mild bleach solution (1 part bleach to 10 parts water). Spray down the plants with one of several powdery mildew solutions.
Related Product: PM Wash, PM Remover
1 Comment

Gwen Bateman - December 02, 2013

Excellent article and very useful suggestions to keep that awful mildew from overwhelming your plants!

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