Tiny White Spots on Cannabis Leaves? Need Help?

During your morning cannabis farming, you notice a few white spots scattered over the leaves of a plant.

It almost looks as if someone splattered them with a white powder.

Unfortunately for you, and for your crop, you’ve just encountered an infestation of White Powdering Mildew (WPM).

It’s a problem most growers will face at one point or another, and one which you should correct as soon as possible.

Keep reading to learn how to get rid of white spots on cannabis leaves.

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What are the White Spots on Cannabis Leaves?

Although it might look benign enough to start, WPM can quickly decimate a crop if not handled immediately.

The patches of flour-like powder are actually a living organism, a fungus, which has taken up residence on your plants.

It slowly eats through the crop, feeding on the sugars inside the leaves to produce even more fungus.

The spores are microscopic, so unlike a pest infestation, you may not see any evidence that it is spreading from one plant to another.

But it will spread quickly, through millions of tiny spores in the atmosphere.

It doesn’t just target cannabis plants; many vegetable farmers are well versed in it as an annoying crop blight.

What Causes White Powdery Mildew on Cannabis Leaves?

You’d be correct to assume that a fungus, like WPM, needs a hot wet environment to flourish.

You’d also be correct to assume this is why they love the environments you've made for your cannabis crop.

The spores may enter into the grow room piggybacking on another plant, within the soil, or on a contaminated tool or person.

If the room has poor ventilation and no air flow, the spores fester in the air, landing on every leaf they can.

High heat, with poor circulation of air, creates a perfect environment to grow WPM.

What Should You Look For When Checking for White Spots?

The fungus always starts as a light dusting of what looks like flour over a few leaves of the plant.

It may target the stem as well, but the leaves are the most noticeable.

It will begin as small circles, and eventually, cover more significant parts of the leaves.

It could look fuzzy, or remind you of the white mold you saw growing on something forgotten in the refrigerator.

The folks over at Marijuana Growers Headquarters describe an outbreak of WPM from start to finish.

Why Inspect Your Crops on a Daily Basis?

Whether you are an indoor or an outdoor farmer, you should get into the habit of frequent crop inspections.

Looking at your cannabis plants on a daily basis, and monitoring their health is an easy way to catch fungus like WPM before it gets out of control.

It’s easy to manage, so long as you can the infestation early.

Even fully automated large-scale commercial growers check their crops daily to ensure everything is going smoothly.

How to Prevent White Spots on Marijuana

A smart grower will optimize the environment to avoid WPM from the get-go.

This means improving air flow through the room (fans and HVAC) as well as improving the ventilation system as a whole.

You may also want to choose certain strains which are resistant to WPM.

Colombia Gold and Thai Sativa are two good options.

Modify your pruning techniques to ensure there is a good breezy air flow through all levels of the canopy.

Also, Implement watering systems which water from the bottom to reduce humidity.

A well designed grow room should not need to rely on fungicides unless of course, the outbreak is severe.

How to Fix White Spots on Marijuana Leaves

But what if you have just noticed the powdering white spots, how can you get rid of them without harming the crop?

The most important step is to remove all infected parts of the plant, or in the worst cases, the plant in its entirety from the grow room.

Destroy it, and ensure it will not have any contact with compost, soil, or tools used on healthy plants.

Explore natural fungicides if the issue is still relatively minor.

These remedies include spraying the plants with a diluted milk mixture, or a combination of baking soda and water.

If the issue is severe, you may need to resort to commercial fungicides.


If you see tiny white spots on cannabis in your garden, you need to act immediately.

The white spots are in fact a living fungus.

The issue can quickly over take your garden ruining your entire crop too.

Thankfully, you can get rid of this fungus easily with a commercial spray or a homemade organic solution.

Were you able to get rid of the white spots?

Tell us what worked best for you in the comments below!

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