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Common Fungal Diseases: Treatment Options [Part Two]

July 5, 2016

There are several ways that professional growers can treat fungus diseases such as powdery mildew, bud rot and root rot when one or more of them attack the cannabis crop. Whenever using one of these treatments, make sure the plant is well coated and remember to get the undersides of the leaves as well. Saturation is the key to success in any remedy.

A few natural remedies that have had some success as organic treatments include:

  • Diluted milk. Using milk has shown positive results, since the dairy proteins in the milk work with the light to create a natural antiseptic. Dilution rates vary depending on severity. This method is best used during bright light.
  • Potassium bicarbonate alone or in a fungicide (such as GreenCure). This treatment affects a plant’s pH, making it a less-than-hospitable host for the spores. Treatment should be done in low light conditions and left to dry before you expose the plants to high-intensity light. It should not be used on seedlings, clones or flowering plants.
  • Hydrogen peroxide. This is a simple yet sometimes effective treatment, used at a rate of 1 teaspoon per gallon of 35% H202. Spray and coat all sides of leaves and plant, then let them dry in low or no light.


Fungicides can be an option as well:

  • Neem oil. This is an all-purpose general fungicide that can be used during the vegetative state to help prevent many maladies such as powdery mildew. However, refrain from using neem oil during flowering.
  • SM-90. This is environmentally friendly and non-toxic. Mix one part SM90 to five parts water. Wet all parts of the plant and let dry. Repeat the treatment a week later if you still see signs of powdery mildew, or as a preventive measure.

Treatment best practices

Here are some best practices when using one of the many options for fighting garden diseases.

  • Some diseases may be regional, and your local grow supply store will know what works best in your area.
  • Do some independent research and ask questions from your local plant professionals and your peers.
  • Try one treatment at a time and keep notes.
  • A heavily infested plant becomes a source of quickly contaminating your entire room. That plant must be removed immediately.
  • Cleanliness is part of overall success. Between cycles, clean and bleach fan blades, air conditioner vents, walls and any other surfaces that could harbor and hold spores. Clean your mother plants and mother room regularly as a part of your standard maintenance program. Create “clean air, clean room” procedures and minimize the number of people who come and go. Cleaning with regularity will help keep your grow from being overrun by diseases.
  • When dealing with fungus diseases, understanding how quickly that spores can travel in the slightest breeze will help you get a handle on the problem.
  • Keep your grow room as close as possible to 45% humidity. Make sure that the air is clean and that the air movement keeps the plants thoroughly circulated. Keep your plants free from being crowded together and unreachable.
  • Finally, when using any of the options on the market to combat powdery mildew, bud rot and other diseases, it is imperative that you follow the guidelines set forth by your state’s regulations and the manufacturer’s recommended dosages.

Ten basic rules for success

The fungus problems you encounter in your garden will vary, but the 10 basic rules are the same:

  1. Always keep your grow areas clean and filter the air, since spores are airborne.
  2. When in doubt, take the plant out. Accept the loss so you can save the garden.
  3. Always use natural products as a first choice. Research which ones work best for your garden and your area.
  4. When you must use any treatment, follow all directions.
  5. Fungicides approved by the Organic Materials Review Institute (OMRI) should be your first choice.
  6. Do not sell or smoke any flower that has powdery mildew or bud rot, since it can negatively affect health.
  7. Know where your plants come from and minimize who accesses them.
  8. Treat plants in the vegetative stage with natural remedies to reduce the need for harmful products in the flowering stage.
  9. Check your plants thoroughly and often.
  10. To identify problems and help predict future ones, keep records of every outbreak, as well as temperature, humidity, air flow and other conditions.


By Eric Stone
Image Credit: By Doc. RNDr. Josef Reischig, CSc. (Author’s archive) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Cannabis Cultivation Today articles are for informational purposes only and should not be considered legal guidance or advice on grow practices. You should contact an attorney or a qualified cultivation consultant for specific compliance and cultivation advice.


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