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Bud Rot on Cannabis Plants: Causes, Symptoms and Treatments

by | Jun 27, 2022 | Cannabis, Environmental Threats, Troubleshooting

Bud rot is a common cannabis bud disease that can be difficult to identify. In this article, we will discuss the causes of bud rot, what bud rot looks like and how you should treat it. We’ll also talk about prevention methods and whether or not bud rot-affected cannabis plants are salvageable.

What is bud rot on cannabis plants?

Bud rot, also called botrytis, cinerea, or gray mold is a disease that cannabis plants may get if it has been in contact with too much humidity or moisture. Some bud rot symptoms include spots on the bud, browning of leaves and buds, leaf mold, and general plant decline. Bud rot is a fungal infection that can affect cannabis plants in every stage of growth but usually rears its ugly head during flowering when you have buds, also called colas. It’s important to note bud rot isn’t going to kill your plant, it will just look bad and cause the buds not to develop properly.

What causes bud rot on cannabis plants?

What causes bud rot is a fungus called botrytis. This causes grey and brown bud spots and is often seen on the bud of a cannabis plant. Environmental conditions like plants that have been exposed to humidity levels that are too high for long periods of time, especially during early flowering stages, are usually to blame. If bud rot is left untreated, the cannabis plant will begin to show signs of bud rot such as discoloration, such as whitish or light brown spots, darkening leaves, and a musty smell. If you can catch bud rot early on it’s usually possible to save your plants; however if the bud rot has run its course it’s essential to destroy the bud and any bud rot infected leaves.

The main contributing factors to bud rot are high humidity and stagnant air. When you have high humidity, particularly humidity over 60%, then you are at a higher risk of bud rot. Fungi love moist environments as they need lots of moisture to be able to reproduce and survive. Also, bud rot may occur when air is stagnant. For example, if you have a fan going that isn’t oscillating and the air around your plants isn’t moving for a while then bud rot may be more likely to develop as there are pools of moisture in these areas where bud rot fungi can thrive.

What are the symptoms of bud rot on cannabis plants?

There are several common symptoms to look for when trying to identify bud rot on your cannabis plants. Bud rot can cause the leaves that are closest to bud growths on the plant to appear discolored, droopy, or curled downwards. This will make it easy for you to spot bud rot at its earliest signs of infestation during vegetative growth stages if your grow room is well lit and has good air circulation.
Bud rot can cause the bud itself to become discolored and have a grey, fuzzy appearance. Sometimes it will appear as though moldy clumps of hair are growing out of your buds or that white threads are covering them from head to toe. This is especially common in the flowering stage when the bud’s resin glands begin producing sugars that bud rot can feed on.

Examples of Bud Rot:

Bud Rot - Zoom Out

Bud Rot – Zoom Out

Bud Rot - Zoom In

Bud Rot – Zoom In

How can I treat bud rot on cannabis plants?

There are many ways to treat bud rot including getting rid of infected plants immediately, lowering relative humidity levels in the growing environment, using fungicides such as sulfur dusts or copper sprays when planting new crops to prevent infection from spreading over from one crop to another.

The most common way to treat bud rot is with a fungicide and cutting out any bud rot before it spreads to other plants. If you find bud rot when the bud is still in a state of growth, it will be possible to save your plant by cutting out the bud with bud rot using clean shears or scissors. After harvesting, if your buds have been affected by bud rot, you should destroy them so that they cannot spread bud rot spores to other parts of your garden. Also be sure to clean your hands, gloves, and shearers before coming into contact with any other plants. If bud rot reaches the flowering stage and has already begun destroying the buds on your plant it is too late to save any part of the bud which was affected. Even if some healthy leaves remain after bud rot infestation there is a high chance that bud rot will return to infect them within the flowering stage. You should remove all affected buds and dead plant material surrounding bud growths as soon as possible during the vegetative stage to avoid bud rot from spreading throughout your cannabis garden.

If you suspect bud rot, it’s very important not to touch any of your plants until you have correctly identified bud rot symptoms. This is because you could accidentally transfer bud rot spores to other plants if they are not yet showing signs of infection, which would spread the infestation throughout your entire cannabis garden as it continues to infect and destroy more parts of your crop with each passing day that goes by.

How can I prevent bud rot on my cannabis plants?

There are several things that you can do in order to try and avoid bud rot in your cannabis garden at all costs. Try not to keep buds too close together; this isn’t usually a problem but bud rot can start to develop between tightly packed buds if there is too much moisture in the air and if you have dense plants. If this happens, you will be able to see bud rot developing before it spreads throughout your entire bud as they are usually easier to spot when they first appear on a few of the surrounding leaves or even directly onto the bud itself.

Another way that you can prevent bud rot is by making sure that your growing environment has good air circulation and avoiding humid conditions by keeping your humidity low. Good air circulation helps to keep the relative humidity low which prevents bud rot from taking hold on buds and spreading throughout your entire cannabis garden with each passing day. Also, remember to monitor your temperature and relative humidity daily. Should you consistently have high humidity during an indoor grow, we recommend purchasing a dehumidifier to get your relative humidity within the desired range. If you have outdoor plants, make sure to space them far apart and check them regularly for signs of bud rot.

Can I salvage any cannabis that has bud rot?

Unfortunately, once you have spotted bud rot in your bud, it’s already too late to save any parts of the bud that have been affected but you don’t have to throw out the entire plant unless the whole plant has been affected by it. If you are lucky enough for the mold spores to not spread through your entire crop before you spot them on a single bud then you will need to remove severely infected buds quickly and completely in order to prevent bud rot from spreading throughout your cannabis garden and infecting healthy plants. After you have removed all of the bud rot on other plants or colas and your humidity and circulation are on point then it should not be able to reinfect your garden.


Bud rot is a common fungal infestation found on plants, especially cannabis plants. It is caused by having high relative humidity and having too much moisture in the air, these wet conditions allow the fungus to thrive. If you have bud rot, there can be fuzzy material on the buds, spots on the leaves, and spots on the colas too. The leaves will also start to contort and curl. Treating bud rot requires removing all affected bud sites and destroying them and using a fungicide as long as it is not too late into flowering.

To prevent bud rot, monitor your humidity and temperature daily and if your relative humidity is too high, you can always add a dehumidifier if it is an indoor grow space. Circulation is also key to preventing bud rot, so make sure to have plenty of it and add oscillating fans if growing indoor plants. Should you have any affected buds, none of them are salvageable and should be disposed of immediately. If you have any further questions, please see our other articles.

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.

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