How to Get Rid of Mold on Weed

by Morgan

June 9, 2021

How to Get Rid of Mold on Weed

It’s pretty easy to identify mold… on bread. Compared to bread, identifying and getting rid of mold on weed becomes a more difficult business where the stakes are considerably higher. 

Once you’ve identified that your marijuana plant is female (not male), you wouldn’t want it destroyed at the hands of an invisible enemy right? So let’s find out what mold is, the different types of it, and how to get rid of mold on weed!

Why is mold bad for weed?

Mold is bad for weed because it can cause physical damage (via enzymes), prevents photosynthesis, and lowers the immune defence of the marijuana plant. It also poses health risks for users who smoke mold-infested weed.

Why is that? In a nutshell, mold is basically a multicellular organism whose natural role is to decompose plants and animals to complete the cycle of nature. Because it lacks a functional digestive system, mold reproduces by releasing enzymes (chemicals) outside its body (and onto your weed plants!), causing damage to the thing it’s feeding on. That’s why you need to fight against moisture in your grow room using tools like the best PAR meter to measure your light source.

Another dangerous quality of mold is its reproduction method. Mold reproduces by releasing spores, which you can think of as super-light, tiny seeds that get released into the environment in search of new areas for colonization. These spores can spread like wildfire if the conditions are right, which is why mold can infect an entire cannabis plantation very quickly.

Finally, because mold likes to create a patchy layer over the leaves, it can block the plant’s sunlight and prevent photosynthesis. This is going to prevent you from growing big buds indoors at best — at worst, your plant will die.

At other times, it might reduce the plant’s innate immune defences, opening up the door for more lethal infections.

What are the different types of weed mold?

The different types of mold include powdery mildew, botrytis, sooty mould, and fusarium. However, it’s the first two types (powdery mildew, and botrytis) that you really need to worry about and that’s what we will cover in this article.

So let’s take a look at how you can identify powdery mildew and botrytis because that’s the first step when it comes to getting rid of mold on weed!

Identifying the different types of weed on mold

One pitfall when trying to identify weed mold is mistaking trichomes for it. This mistake could lead to disaster because trichomes are what store the good thing about weed, which is cannabinoids.

Trichomes are hair-like structures, and a plant that’s covered with too many of them could be mistaken for a mold-infected plant. One easy way to differentiate mold from trichomes is to smell the plant carefully. If the plants smell like grass, this could mean what you’re looking at is mold.

Another way is to look closely and see if changes caused by mold are visible on both the leaves AND the trichomes. If this is the case, then you can be sure that you’re not about to destroy a good, plump, cannabinoid-loaded plant. Said another way, mold will attack the entire plant so if you see the white powder engulf an entire area, it’s likely mold and not delicious trichomes.

Powdery mildew mold

But what changes are we looking for? Well, that depends on the type of mold. If it’s powdery mildew, then you’ll notice white, powdery patches over the leaves. Now, these will look very similar to trichomes, so be careful. With powdery mildew, you’ll also notice that the plant has stunted growth and some plant tissue may appear discolored.

Botrytis mold

With botrytis, you’ll notice the exact opposite — small black dots appearing on infected structures. You may also notice a gray patch forming over the plants, and infected plants will begin to discolor and die. 

Note that both botrytis and powdery mildew thrive well in humid conditions. So environmental cues (like the time of the year and surrounding humidity levels) will help you in determining whether a plant is infected.

How to get rid of powdery mildew on marijuana?

To get rid of powdery mildew on marijuana, there are a few methods you can follow, including, spraying the leaves with an antiseptic solution, wipe them with a wet towel, or simply cutting off the infected parts.

A popular antiseptic spray that can be easily prepared at home involves mixing 2 teaspoons of apple cider vinegar with some water. Other options include sprays prepared from sesame and neem seed oils, fish oil, and a spray made of milk and water.

Another method is the wet towel method, which involves just applying a wet towel to the infected surface. Be careful not to manipulate the leaves around too much because that could lead to spore release and spread of the fungus to the entire plantation.

If you don’t want to trust sprays or water, consider cutting off the infected part if the mold hasn’t spread too much. 

It’s very important to note that once the mold infects the buds, it will be almost impossible to get rid of it. So you must stop the infection from reaching this point, and a good way to do this is to prevent powdery mildew from developing in the first place — prevention is (far) better than cure! (That’s why we recommend having an excellent light source for your plants, like the Mars Hydro TSW 2000w grow light or the Spider Farmer 4000 grow light).

Powdery mildew thrives the best in overcrowded, humid conditions where the leaves are in contact with each other. The simplest way to prevent mold from growing is to deprive it of these conditions.

This mainly involves allowing plants ample space to grow and controlling humidity via dehumidifiers and adequate indoor lighting in the environment (checkout our piece on the best indoor grow lights for your marijuana plants). Other ideas include using preventive sprays, giving just the right amount of water and doing so in sunlight to help evaporate extra moisture, and discarding infected plants properly to prevent infection spread.

How to save cannabis plants from botrytis?

To save weed plants from botrytis, identify and destroy the affected parts. Sprays are not really useful when it comes to botrytis, so the only way to get rid of it is to identify it correctly and then remove the infected parts to prevent infection spread.

In addition to thriving well in humid and cool conditions (just like powdery mildew), botrytis infects plants via wounds and openings, which makes keeping pruning tools clean and sterilized an important part of fighting this type of mold.

You also need to discard the pruned parts properly to prevent spore release and further spread of infection. 

Finally, just like with powdery mildew, keeping humidity levels under control is an important part of fighting against botrytis. Consider making use of humidity sensors to keep the moisture from rising to dangerous levels. Good use of indoor lights is another way of fighting moisture (which can also help prevent hermie plants).

How to get rid of mold on flowering weed plants?

Depending on the type of mold, treating mold on flowering plants involves the same steps as described above.

You should note, however, that it’s the flowering plants that are at the highest risk for developing a mold infection. That’s because as flowers increase in size, the air flow within a plant decreases, increasing the risk of spore colonization and subsequent mold infection.

So make sure to pay special attention to your plants at this stage because a mold infection at this point can force you to harvest the plant before the ideal time, reducing its quality. 

How to get rid of mold on cured weed?

Getting rid of mold on cured weed is not possible; your only option at this stage is to discard the infected weed, that’s why we wrote a guide on drying weed! You should never try to smoke mold-infected weed because it can lead to significant lung problems (such as pneumonia), especially if your immune system is compromised.

At other times, your immune system might react too violently to the mold, leading to an allergic reaction that involves symptoms like wheezing, runny nose, and shortness of breath.

However, just like marijuana plants, cured weed is more susceptible to mold infection under cool and humid conditions. One weed hack we recommend is saving it from infection by storing it in an air-tight jars at around 25 C. Also, try to keep the container in a dry, dark place because moisture and sunlight make an ideal breeding environment for nasty mold!

Now you know how to get rid of (and prevent) mold on weed!

Although sprays and wet towels can cure certain types of mold infection, prevention is really the key because once a plant becomes infected, there’s a very high possibility that it will infect neighboring plants. The situation can deteriorate rapidly, so stopping a mold infection before it develops is an easier thing to do.

This can be easily accomplished by controlling environmental parameters like humidity, daily lighting, temperature, and plant spacing to deprive mold of ideal conditions!

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About the author 


I discovered the benefits of Cannabis at a young age in 2002, with years of trial and error, my knowledge grew just like my plants. As my love for cannabis unfolded I began to teach and learn, trying to gain as much information and practical growing experience.

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