How to Identify, Avoid, and Treat Powdery Mildew on your Cannabis

Did it snow today? No, of course not, this is Southern California and you’re indoors. Then what is this white powder that seems to be covering all your cannabis plants? You know it’s not snowing, and your weird uncle that has dandruff has already left town. What could this be, and why is it ruining all of your plants? Then it hits you, mildew! A grower’s worst enemy when trying to maintain a proper harvest. Mildew is something that is extremely common when growing cannabis. This pesky white powder has ruined people's crops time and time again. Then what’s the solution? Knowing how to identify, avoid, and treat your plants when afflicted with it will help you produce a happy and healthy plant.

I Spy Mildew!

Whether you’re growing indoors or outdoors your cannabis plants are susceptible to powdery mildew. Mildew, by definition, is a thin whitish coating consisting of minute fungal hyphae, growing on plants. This fungus is a quick spreading white powder that if not treated promptly will result in ruining your entire harvest.

Treatment Time

If your plant has already been affected by mildew you need to take action as soon as possible. There are many methods of treatment for mildew, some organic, some store bought, and some can be found right in your cupboard. The first thing you want to do to see if you have this fungus in the first place is to check and see if you have any blistering on the tops of your leaves, if so, you have mildew. If so, you need to prune your plant immediately. Removing any of the infected leaves is the first steps in combating mildew before it reaches to the buds of your plant. If your plants are already covered in powdery white fungus then a second step to take would be to carefully wipe the infected leaves. Be careful when doing this step because you don’t want to move too quickly or else you will knock mildew on some parts that may not be affected.

After that it’s up to you on how you want to extract the mildew from your plant. Believe it or not, growers have found that milk is a great way to eliminate mildew because of the microorganisms found within it are great when combating this fungus. You can also go to any hardware or gardening store to purchase the many fungicides that are on the market to spray on your plants as well. For the all-natural growers out there you can use 2-3 tablespoons of apple cider vinegar per gallon of water and spray on your plant to reduce mildew. If you can’t find apple cider vinegar at

home try using baking soda. All you need is 1 teaspoon per gallon of water and spray just like you would the vinegar.

Mildew Avoidance

Now that you know how to treat mildew the next question is, how do I avoid it in the first place. The three key factors in avoiding mildew are spacing, humidity, and ventilation. When it comes to spacing you’re going to want to keep your plants 25 cm to 46 cm apart. Think of it this way, say you’re at a concert and everyone is standing by the stage trying to get the best view. With all of those people huddled in that area it’s bound to get hot and humid because of the lack of space between bodies. This is the same with plants, especially if you have a grow room. Letting your plants get an ample amount of room to grow and breathe is extremely important in mildew prevention.

Humidity levels, like mentioned with plant spacing, is one of the most important factors in preventing mildew as well. Mildew thrives on moisture which is why monitoring your temperature and humidity levels are crucial when growing cannabis. If it’s hot inside your grow space you’re practically inviting fungus to join the party. Although you need some humidity to ensure your plants to grow, monitoring your levels and temperature within your area is something that can keep you ahead of the game to ensure your plants can avoid this fungus.

Lastly, tying into humidity and spacing for mildew prevention is ventilation. If you’re growing in an enclosed space you’re going to need fans to ensure proper airflow. When lacking fans your room becomes stuffy which results in humidity which now we all know now results in mildew. Because of the humid air, it makes it easier for spores to land on your plant’s leaves and take over them with their powdery white fungus. Purchasing fans will help your plants feel fresh and have the heat pulled away from them to reduce the humidity. Taking the proper precautions for your plants will only save you time and money in the long run. Understanding how you can take the right steps in preventing mildew will allow you to become a smarter grower ensuring your buds will be fresh and ready for harvesting.