Does powdery mildew kill the plant?

It can eventually kill the plant by blocking photosynthesis and weakening the immune system. It also makes the buds unsafe for consumption.

Can I wash the mildew off?

You can wipe it off, but the spores remain on the plant. You must treat the environment and the plant to stop it from coming back.

Cannabis: spots, causes and fixes

Check these first

Rub the white spot with your finger to see if it wipes off.
Check the humidity levels in your grow space.
Ensure your fans are moving air around the canopy.

Likely causes

Powdery Mildew
Most likely
How to tell: The leaves will look like they have been dusted with flour or talcum powder. It usually starts as small circular spots and spreads to cover the whole leaf.
What to do: Remove the most affected leaves immediately and dispose of them away from your grow area. Increase airflow with fans and lower the humidity to below 50 percent. Treat the remaining foliage with a mixture of 1 part milk to 9 parts water or a commercial fungicide.
Calcium Deficiency
Possible
How to tell: These spots are usually brown or rust colored rather than white and dusty. They often appear on the middle to upper leaves of the plant.
What to do: Check your soil pH to ensure it is between 6.0 and 7.0 for soil grows. Add a calcium and magnesium supplement to your next watering to correct the imbalance.

Leaf spots on other plants

Find out what's wrong with your cannabis

The list above covers the usual causes. Pocket Botanist looks at a photo of your actual plant and tells you the likely cause, how serious it is, and what to try first. Identification and a health check are free.

When to worry

If the mildew reaches your flower buds, it is usually best to discard those parts to avoid smoking mold. If the infection covers more than half the plant, it is very difficult to save.

Stopping it coming back

Maintain a consistent humidity level and ensure your plants are not crowded. Proper spacing allows air to move freely through the branches.

Cannabis: spots? Check yours with a photo

Every plant is a little different. Take a photo of your cannabis and Pocket Botanist tells you which cause is most likely, how serious it is, and what to try first. A few checks a day are free. Save the plant and you get care reminders timed for it.

Get the app · Or check it from a photo now, free

Questions people ask

Does powdery mildew kill the plant?: It can eventually kill the plant by blocking photosynthesis and weakening the immune system. It also makes the buds unsafe for consumption.
Can I wash the mildew off?: You can wipe it off, but the spores remain on the plant. You must treat the environment and the plant to stop it from coming back.

Guides to these causes

Powdery Mildew

What are these white dusty spots on my cannabis leaves?

Check these first

Not sure what's wrong with your cannabis?