Everything you need to know about growing cannabis at home

Powdery Mildew on Cannabis Plants: Prevention and Treatments

by | Jun 13, 2022 | Cannabis, Environmental Threats, Troubleshooting

Powdery mildew is a common fungus that can be found in many gardens. It’s important to learn how to identify powdery mildew fungi, what causes it, and how you can prevent or treat it before the spores spread. Powdery mildew starts out as small white patches on the leaves of plants which then turn into yellow-green cotton-like substances. Plants with powdery mildew are less healthy because they have lost some of the chlorophyll that helps them photosynthesize. If you want to get rid of this pesky problem once and for all, we will provide you with some steps on how you can treat your plant at home. Read on to learn how to identify, treat, and prevent any powdery mildew in your garden.

What is powdery mildew?

Powdery mildew is a fungus that affects many different types of plants, including grapes in vineyards and cannabis. The powdery mildew spores can be spread by wind or contact with other infected plants. For the most part, the fungal disease is not fatal to healthy plants and will eventually go away on its own when environmental conditions improve. However, if left unchecked for too long powdery mildew can cause irreversible damage to leaves and fruit.

There are three different types of powdery mildews: Erysiphe polygoni (very common), Oidium lactis (less common), and Leveillula taurica (rare).

The most common type of powdery mildew fungus is caused by Erysiphe polygoni, which affects a variety of plants. All are in the scientific order Erysiphales.

What causes powdery mildew on cannabis plants?

Powdery Mildew thrives in moist and humid conditions that aren’t too cold or hot. Powdery mildews are most common during warm spring days when there’s plenty of moisture in the air. The fungus feeds on plant sap and breaks down chlorophyll, which causes infected leaves to become yellow or white. Spores are then sent out onto other plants that haven’t been treated with fungicides. If you want powdery mildew treatment to work effectively, it’s important to use preventative measures before your plants have contracted an infection.

Powdery mildew occurs during indoor grows because the relative humidity is too high and there isn’t enough air circulation. Indoor growers will use fans, gauges, and exhaust systems to monitor and prevent this.

Symptoms of powdery mildew on cannabis plants

To treat powdery mildew you must first know that it is powdery mildew. You can identify powdery mildew by the powdery white coating of mold on leaves. This fungal growth will show as powdery spots on the leaf surfaces of susceptible plants with too much moisture and humidity and not enough air circulation. Leaves will turn yellow and die, which causes your plants to lose their green color. If left untreated, powdery mildew can cause fruit to drop early. It can also stunt your plant and take away some of its nutrients.

How can I treat powdery mildew on my cannabis?

The first step to treating powdery mildew is by identifying it correctly on your plants. Take some time to notice the symptoms of powdery mildew on leaves and stems before trying any home remedies for powdery mildew treatment. Once you know what you’re dealing with, it’s time to start administering fungicides. Spray in the morning or evening when temperatures are lower and humidity is high because powdery mildews thrive under these conditions.

There are also homemade remedies that work very well for powdery mildew. Some of the homemade remedies are baking soda, milk and water solution, or hydrogen peroxide. It’s important to spray your plants every few days until the powdery mildew has disappeared from leaves completely because it can reoccur if not treated properly.

Preventing powdery mildew on cannabis plants

Prevention is always better than cure when dealing with powdery mildew, so learn how to prevent powdery mildews before it’s too late. Make sure your plants get enough sunlight, or artificial light if in a tent, and keep them well-watered without over saturating the soil or drowning your plants.

It is also important that you plant species of plants that are less susceptible to powdery mildew in place of those with a history of powdery mildew infestations. Some plant varieties that are less susceptible to powdery mildews include beans, cabbage, cauliflower, celery, and onions. There are also certain strains of cannabis that have been shown to be best at preventing powdery mildew, examples being Northern Lights and one of its offsprings Super Silver Haze.

If growing indoors, the best temperature and humidity to prevent powdery mildew are between 55 and 77 degrees Fahrenheit (13-25 Celsius) with humidity below 60% for indoor grow rooms. You also want to remove any dead leaves or heavily diseased leaves and wash your pruning shearers after removal. Pruning your plants to promote airflow is also essential for prevention along with maintaining proper spacing away from any other plants or walls.

DIY solution for powdery mildew on cannabis plants

If you opt for the do-it-yourself version we are going to provide several recipes below. All the ingredients are available in most households, and if you don’t have an ingredient they should be available at any grocery store. To treat plants at home with powdery mildew follow these steps:

Baking soda treatment

You can make a baking soda treatment with a few simple ingredients:

  • 1 tablespoon of baking soda
  • 1/2 teaspoon of liquid soap (make sure that it is not detergent)
  • 1 gallon of water

Mix all the ingredients together and spray liberally on the plants as a preventative measure or to treat them. Use every few days until the symptoms stop.

Natural fungicide

These treatments work but may expose your plants to harsh chemicals. These can be bought at any hydroponic store or garden center and you should follow the schedule they list on the bottle.


If you want the most all-natural solution then this is your best bet! Take one part milk and mix it with 2 or 3 parts water and apply it liberally to the leaves every day until the powdery mildew is gone. That’s it!

There are plenty other recipes too, another common one uses potassium bicarbonate instead as the active ingredient. You may notice recipes that are similar to this and they may also work. A lot of gardeners tinker with the recipes to figure out a solution that works best for them and their plants.


Powdery mildew can be devastating in the garden, but there are many ways to prevent and treat powdery mildews on plants at home. You can either take a DIY approach or apply fungicides when identifying your plant with powdery mildew infection. For best results, it is important that you use both preventative and treatment measures to ensure powdery mildew doesn’t reoccur on your plants.

To learn more about growing cannabis at home consider checking out our guides on: Getting Started, Troubleshooting, and Optimizing your Grow or search our Knowledge Base.

We strive to help your plants thrive.