Bud Rot: How to Deal with Grey Mold | Homegrown Cannabis Co. (2023)

Bud Rot: How to Deal with Grey Mold | Homegrown Cannabis Co. (1)

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Pathogens, including bacterias, viruses, and fungi, are present in all living things.

These microscopic molecules are required for us to survive, and some can be harmful and cause a variety of problems.

Cannabis plants are no different and can get infected by deadly particles. One of the worst is called bud rot, also known as grey mold or botrytis.

It’s a fungal disease that can completely take over a marijuana crop.

If you’re a grower, it’s vital to know the causes, signs, and how to control cannabis bud rot to ensure a healthy yield.

Continue reading to find out more about bud rot and how to protect your precious plants.

Bud rot – the most common cannabis mold

Even the most experienced growers can face the problem of bud rot in weed. It’s hard to avoid because the fungus can travel through air, water, clothing, animals, and clones.

What causes marijuana bud rot?

The fungus and marijuana plants thrive in the same environment. Grey mold prospers in humid and cool temperatures.

Bud rot doesn’t care if the plant is still sprouting or fully mature. It’ll attack anything in its way and spread fast. As soon as you realize there’s a problem, it’s present, and many of your crops might be dying.

Bud Rot: How to Deal with Grey Mold | Homegrown Cannabis Co. (4)

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(Video) How To Deal With Cannabis Bud Rot - Growing Pains

What is bud rot?

Bud rot is a mold that Botrytis cinerea, a fungus, causes. It’s a common problem with cannabis, so the weed-growing world named it “bud rot.” It describes what the fungus does to the plant; rots buds from the inside out.

Outside the cannabis world, gardeners refer to it as grey mold because of its color. The fungus enters the plants through vulnerable areas such as the roots, wounds, tears, fresh cuts from pruning, or insect damage.

What does bud rot look like?

Bud rot usually attacks young stems, as they’re more fragile. The first signs begin right where the sprouts meet the soil. The typical bright green stems will be dull and soft, which means they’re experiencing damping off.

That doesn’t mean that your more mature plants are safe from bud rot either. As soon as the fungus attacks, it’ll take whatever it can get and kill larger crops.

Bud rot signs start with white color and a fluffy texture, like powdery mildew, and will be inside the buds. As it matures, the fungus turns to a dark greyish mycelium mass, and the stems of your plants will be soft. You’ll see grey spots all over infected cannabis.

Bud rot can show itself in other ways as well. Here are some other signs to look out for.

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Discolored buds

If one area of buds is starting to look dry or discolored, look at the stem for grey mold. The buds will have patches of black, grey, or brown. The texture will be dry and crumble easily. Even if all other parts of the plant appear healthy, it doesn’t mean it’s safe.

On mature plants, the fungus will attack the wettest parts first because it loves humidity. The leaves closest to the water mister or farthest away from the air supply are at risk.

Dark and dried up colas

The cola is a cluster of buds that are tightly together. It forms on the upper section of the main stem. If the cola is dark brown and looks dry, it could be a sign of bud rot.

Yellow leaves

Before the discoloration, leaves can start to wilt. As the grey bud rot mold matures, the leaves will go from a vibrant green to yellow due to a lack of chlorophyll. Then, they’ll become slimy and limp.

The fungus sucks all of the nutrients out of the plant, causing it to die.

How to treat bud rot

If you notice some of these signs in your cannabis plants and are afraid the bud rot will take over your harvest, don’t panic yet. There are ways to treat the problem before it’s too late.

You’ll need to move fast, as the pathogen infects at an exponential rate. Bud rot can kill a whole garden in just one week. Don’t know what to do? Watch the video below and keep reading to find out more about the bud rot cure.

(Video) Dealing with Cannabis Bud Rot | Homegrown Cannabis Co. Garden

1. Remove all affected buds

When the fungus is present, it’s not about saving the infected plants. Instead, your goal is to protect the healthy crops from the pathogen. You’ll need to remove all affected buds.

In some cases, that means trimming a few leaves off the stem. Other times, you’ll have to remove a whole plant; roots, stem, and all.

During this stage, it’s vital not to let any fungus touch other crops. You might need to take the pot out of the environment before pruning.

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2. Ensure the rest of the plant is Bud Rot Free

Once you take care of the obvious, it’s time to be an inspector. Bud rot moves quickly, so it’s possible it’s in other parts of the plants that aren’t very visible.

Take the time to search and see if all crops are bud rot free. That’s the only way the problem will stop, and you can continue growing healthy plants.

3. Let the Buds Continue to Ripen (If You’re Certain the Environment is Fixed)

During the next few days and weeks, keep an eye on your harvest. Let the buds ripen and grow as they should. If you see any grey mold appear again, you’ll need to repeat steps 1 and 2.

4. Harvest the Plant Immediately (If You Can’t Fix the Environment)

In some cases, the bud rot can take over your whole growing area. As much as you remove the infected areas, grey mold is still in attack mode.

When this happens, you’ll need to harvest all mature leaves and move them to another area. You’ll need to discard the rest.

Empty the soil and clean containers thoroughly with a disinfectant. Clean the space by wiping down the walls, tables, tools, and any other material you use while growing. Let the space air out to remove the moisture.

From there, you’ll have to start from day one with new soil and seeds.

How to prevent bud rot

It’s much more effective to prevent a problem with your cannabis plants than try to fix one. For example, if you never gain weight, you’ll never have to worry about dieting to lose it. The same goes for mold. Here’s how to prevent bud rot.

Creating the right environment and maintaining it will assist the health of your cannabis crops.

In the garden

The garden is where the growth happens. Cannabis likes a humid environment, which is why it’s so prone to a pathogen attack. Bud rot also thrives in moisture. Regardless, there are ways to manage the space to please the marijuana and keep fungus at bay.

(Video) How to deal with mold and bud rot when harvesting your cannabis flowers

Monitor humidity

The ideal humidity during vegetation is 40% to 70%. Once the plants start to flower, you should reduce the level to 40% to 50%. Then, as the plant matures, you can drop the humidity to 40% or lower.

You use a hygrometer to measure the percentages in the garden. To maintain the right levels, use a dehumidifier or have a ventilation system for airflow.

Be aware of any puddles or still water in the growing room, as the fungus can grow here and then pass through the air to plants.


Pruning leafy plants is a way of preventing bud rot. When leaves are close together and touch, it creates wet spots. Trimming bigger leaves will give the others room to breathe and dry out between watering.

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Training a plant is when you control the direction it grows. Usually, you do this with a pole, and as the stem gets bigger, the farmer ties the two together.

Training helps manage plants and is ideal for indoor gardens. It reduces the cause of bud rot because you can make sure the plants aren’t touching or growing into each other. There’s enough airflow from plant to plant. It also assists in reducing the spread of bud rot.

Try a different watering schedule

You never want puddles of water or a too moist environment. If you notice your plants are constantly damp, you might want to change your watering schedule.

Reduce the number of times a day you water so that the cannabis can drink up all the H2O on the soil. Remember, at different humidities and times of the year, plants behave in varying ways.

You can test different schedules and see which one is best for your plants and environment.

Amend nutrients

Soil amending is when you add material into the earth to make it an ideal place for crops. Without this, your plants might be sucking up too many nutrients from the ground, leaving them vulnerable to infection.

Once the nutrients are gone from the soil, your plants will also become weaker with the lack of food. Your cannabis won’t be strong, and if bud rot appears, it’ll attack quicker.

Amending nutrients will increase the soil’s quality, which keeps it and the crops strong and fed. This is a great way to prevent bud rot from making a home in your garden.

In the drying room

Once the marijuana leaves reach their total growth, farmers must harvest them. Before they’re ready to be smoked or processed, they must dry out.

The garden is a humid, warm oasis, while the drying room is quite different. Bud mold after harvest is still possible. The fungus can creep into your drying room and strike. We’re going to go over ways on how to keep this stage bud rot free.

Harvest buds when dry

When it’s time to harvest your weed, make sure the leaves are dry. You’ll know your watering schedule, so plan accordingly.

(Video) How to deal with Bud Rot, Gray Mold, Stem Rot, Botrytis... A Cannabis Growing Support Video

By doing this, you reduce the risk of bringing fungus into your drying room, as it loves wet places. If you notice some leaves are damp, shake them or give them proper airflow before leaving the garden.

Remove fan leaves

Removing big fan leaves when mature will help reduce bud rot. These spread out and can clutter the garden. If they’re too big, they can abstract airflow.

Taking fan leaves to the drying room will ensure your sizable healthy crop stays that way and creates space for the smaller plants to grow.

Leave space between buds

Even in the drying stage, you’ll want to leave space between each bud. This is for two reasons. The first is to ensure proper airflow so that the marijuana can dry efficiently. The following explanation is that chance bud rot is present, so it won’t jump from leaf to leaf with ease.

The fungus hates dry and cool areas, so it might die before it can infect all the crops.

Create the perfect drying environment

The drying process takes about 15 days, depending on the environment. The ideal temperature for a drying room is about 68℉ or lower. You don’t want anything warmer because the cannabinoids and terpenes can evaporate.

The humidity level should reduce down to 40% or lower. The idea is to take out moisture slowly. To manage the levels, make sure there’s quality airflow around the room. Never blow air directly on the leaves, but instead use a ceiling fan on low or use a window for natural breeze.

You want to create a dark place for a better quality product. The chlorophyll will preserve better, and that affects the taste.

Ensuring your drying room is perfect will help reduce bud rot because the fungus cannot survive in these conditions.

Bud Rot: How to Deal with Grey Mold | Homegrown Cannabis Co. (10)

Stop bud rot before it starts!

Doing things right the first time around will save a lot of headaches in the future. If you’re a new grower, understanding all these details can be overwhelming, but not paying attention will result in problems.

You’re unlikely to have a problem with bud rot if you follow the preventative steps and continue to monitor your crop. Attention to detail and patience will help you grow healthy mature marijuana, bud rot free, that you can enjoy recreationally or sell if your location allows.

Now you know what bud rot is and what a nightmare it can be. If you have a plant or fifty on the go, head out and check to make sure everything is in place. If you’re a new grower, start planting.

What are you waiting for? You know how to prevent bud rot and the perfect ways to ensure healthy growth. All that’s left to do is buy some seeds and get planting!

About the author: Parker Curtis

Parker Curtis has around a decade of cannabis-growing experience, specialising in soil-less and hydro grows. He’s mastering outdoor, greenhouse, and indoor grows.


Can you save a cannabis plant with bud rot? ›

After bud rot has set in, there's not much you can do to reverse the spread of the fungus. If you notice a section of your garden has bud rot, there's a strong possibility that the rest of your garden is infected too. To prevent the fungus from spreading, remove all infected plants.

What kills bud rot spores? ›

ZeroTol is a powerful broad-spectrum bactericide and fungicide that kills algae, bacteria, fungi, and their spores on contact. It's a PERFECT solution for getting rid of Bud Rot in your gardens and sanitizing your plants just before harvest.

How do you control Botrytis in cannabis? ›

Controlling humidity in cannabis greenhouses and grow rooms is the number one method to prevent botrytis. So using dehumidification is the only sure-fire way to reduce and even eliminate botrytis outbreaks. DryGair is designed specifically for this purpose.

Can I salvage Bud Rot? ›

Can you get rid of mold on bud? Some growers may swear by the use of hydrogen peroxide or Neem oil to stop mold in its tracks but the absolute best and safest way to deal with moldy weed – is to toss it. Once infected, spores spread very quickly. Infected areas of the plant should be carefully chopped and tossed.

Can you control bud rot? ›

Preventing bud rot by controlling greenhouse or grow room climate conditions is without a doubt the most effective option. However, there are several other measures growers can use to help prevent bud rot or its symptoms. The most common of which is neem oil.

What temperature kills bud rot? ›

Most experts recommend temperatures above 68°F to keep bud rot at bay. In a greenhouse, try to avoid cold nights by using a heater.

Does baking soda help with bud rot? ›

On the other hand, the baking soda and lemon juice used to wash cannabis can kill mold spores and therefore may help prevent mold from growing during drying, curing and storage. However, washing cannabis will not remove advanced mold or “bud rot” that is already present at the time of harvest.

What is water curing for bud rot? ›

Place the cannabis flower in a large flat bowl and pour running water over it gently. Do this for about 10 hours and the cannabis is cured. It is not the best technique—you'll lose a lot of flavor and will potentially damage your buds but it is indeed possible.

Can you get rid of bud mold? ›

The best way to get rid of mold on cannabis plants in your grow room is to dispose of any moldy weed immediately, then have the area professionally treated. This will stop the mold growth in its tracks and save the rest of the crop. Make sure there's plenty of ventilation and good airflow in the space.

Can you remove mold from buds? ›

Is there any way to remove the mold? Not really. You may be tempted to cut off the obviously moldy bits and smoke the rest, but it's not a good idea. Life's too short for bad bud.

What temperature kills Botrytis spores? ›

The results demonstrated that B. cinerea spores can be inactivated by heat treatments using relatively low temperatures (42-46 °C).

What is the best spray for Botrytis? ›

Daconil® Fungicide Concentrate simplifies protecting larger garden areas from botrytis blight's threat. Measure concentrate into a hand-held, hose-end, or tank-style sprayer with the convenient measuring cap. Then add water, mix well, and spray until all plant surfaces are thoroughly covered.

What chemicals are best for Botrytis? ›

Prevention & Treatment
Active IngredientExamples of Brands & Products
Copper FungicidesNatural Guard Copper Soap Liquid Fungicide Conc.; & RTU
Southern Ag Liquid Copper Fungicide (copper ammonium complex)
Neem OilBonide Rose Rx 3-in-1 Concentrate; & RTU
Bonide Neem Oil Concentrate; & RTU
31 more rows
Jul 23, 2021

Does Bud Rot affect potency? ›

It affects the potency, the smell, and the flavor of your favorite strain — and not in a good way. Moldy weed can even cause some rather serious health problems, so it's vital to know how to check your bud for rot and what to do if you find it.

How do you clean a grow tent after bud rot? ›

Step 1: Take everything out of your grow tent to give you easy access to the inside surfaces of the canvas. Step 2: Use water to rinse off some of the grime from the canvas surfaces. Step 3: Use 3% hydrogen peroxide or bleach to disinfect the surfaces. These cleaning agents can kill any germs the water left behind.

How do you prevent bud rot in high humidity? ›

Keeping Bud Rot at Bay with Humidity Control
  1. Keep Air Moving. Air movement is key to keeping a healthy crop—both above and below the canopy. ...
  2. Manage Your Canopy. ...
  3. Don't Entirely Count on HVAC for Dehumidification. ...
  4. Avoid Under-Sizing Your Dehumidification Needs. ...
  5. Seal Your Room. ...
  6. Keep Your Temperatures in Check.
Nov 7, 2017

Is Bud rot inevitable? ›

Bud rot is often considered an inevitable phenomenon, a yield loss that every weed grower has to face. But, you can stop your plants from suffering the same fate.

How long does it take for bud rot to grow? ›

Outdoors you may get patches all over the plant, especially after a few rainy days. With bud rot, certain areas on the colas (buds, pistils and/or leaves) start dying, unlike the rest of the plant. The changes happen quickly, within just a day or two.

What kills Botrytis? ›

Mycostop, a biological fungicide approved for organic use, has shown suppression of the disease. Direct spray (5 gm/ 50 liters of water) to susceptible leaves, flowers and fruits to point of run-off. Apply every 2-3 weeks, or as needed depending on disease pressure.

Is powdery mildew the same as bud rot? ›

Unlike bud rot caused by Botrytis cinerea, powdery mildew can't be stopped by simply drying out the atmosphere. Many growers think of powdery mildew as a dry mold because it can spread rapidly in environments with relatively low humidity levels. This is because the devil is in the details.

What temp should I cure my buds? ›

Once your buds are tucked away in their jars, place them in a dark area and double check the environment. The optimal temperature for curing remains at 70 degrees Fahrenheit or 21 degrees Celsius. However, the process requires a slightly higher humidity level of 60-65% as compared to the drying stage.

What happens if I put too much baking soda in my plant? ›

But practically speaking, it's not ideal. Because high concentrations of sodium are toxic to plants, if you dump a bunch of dry baking soda onto a small plant, it will probably die. Also, because sodium is soluble, it's likely to hurt or kill nearby plants that you didn't want to harm.

How do you wash buds with hydrogen peroxide? ›

Fill the first bucket with water and add the cleaning agent of your choice. If you're using hydrogen peroxide, which is particularly good for removing powdery mildew spores, you should add between 10ml and 12.5ml of 3% hydrogen peroxide to each litre of clean water.

How do you tell if buds are dry enough for curing? ›

When Do I Know My Buds Are Properly Dried And Ready To Cure? There's a simple test to know if your buds are dry: Simply take a small branch and try to bend it. If it snaps, your buds are dry and you're ready to move on to the curing process. If they bend, your buds need a little longer to dry.

Can you save bud with powdery mildew? ›

Unfortunately, once powdery mildew is on your plants, it is nearly impossible to remove. Your only chance of saving the crop is by very carefully bagging and removing all infected plants from your grow areas.

How do you dry mildew buds? ›

If it's hot, we recommend drying your buds in a lightly air-conditioned room. You can also use air-conditioning to drive down the humidity if you live in a particularly humid area. Finally, remember to use fans to circulate the air around your buds to dry them evenly and further prevent mould from forming.

What removes mold permanently? ›

Bleach kills virtually every species of indoor mold that it comes into contact with including mold spores which leaves a sanitized surface making it resistant to future mold growth.

Can plants fight off mold? ›

Many species of indoor plants can actually help absorb mold and spores. Studies have shown that rooms with air-filtering houseplants can improve this air quality by 60%. It is highly recommended to keep one good sized house plant per 100 square feet to help clean polluted or dirt-filled air.

Will powdery mildew hurt my buds? ›

If not treated early, powdery mildew will continue attacking your crops by damaging the leaves, petioles, stems and buds. If left to progress, your plants will be unsuitable for smoking. Powdery mildew is a common fungus for cannabis crops.

How do you treat gray mold? ›

Gray mold is common in wet or very humid conditions. The best way to prevent gray mold is to space out plants so they have room to dry out after rain or watering. Remove infected flowers, leaves and stems. Infected plant parts should be buried or composted.

Is GREY mold harmful? ›

Is Grey Mold Dangerous? Depending on what type of species the grey mold is, it may be dangerous. A few types of mold will produce something called mycotoxins, which can harm you. Grey mold can sometimes be harmless, while if it's actively growing on water-damaged building materials, it can off-gas.

Is GREY mold airborne? ›

In high relative humidity, the fungus may sporulate on infected tissues and produce masses of characteristic gray or brownish spores that become airborne, which is primarily how the fungus is disseminated.

What is a natural fungicide for Botrytis? ›

Neem oil acts as a natural fungicide, and can help reduce the concentration of fungal spores. Applying neem oil regularly, as a preemptive measure, can drastically reduce the chances of a botrytis breakout.

How long do Botrytis spores last? ›

The most common and damaging infections take place through leaf-scars during de-leafing operation where Botrytis spores can remain dormant for 10 to 12 weeks. Such spores can be triggered to germinate by low light, plant stress or shift in fruit load.

Is Botrytis contagious? ›

Botrytis cinerea spores are always present. Botrytis spores are easily spread by wind, humans and water. The spores germinate at a temperature between 2°C and 32°C.

What fungicide is used for Botrytis? ›

Recommended single-site fungicides during bloom for either Botrytis species are newer category 7 (SDHI) fungicides (Merivon, Kenja, Fontelis, and certain products in the Luna series). They can also be applied during ripening if needed.

How do you chemically control Botrytis blight? ›

Chemical Control

In case of early infections, foliar sprays with chlorothalonil can be applied to control its spread. Other fungicides based on fluazinam, and thiophante-methyl can also work. The development of resistance is common when fungicides are used intensively.

What is the foliar spray for Botrytis? ›

As a maintenance foliar spray, Physan 20 will prevent Botrytis, black leaf spot, powdery mildew, Rusts, Blights and Rot (such as Erwinia). Physan 20 can also be used to treat and cure Rot upsets such as Crown Rot and Root rot.

Does Bud Rot ruin a whole plant? ›

Botrytis cinerea is a parasitic fungus that has two recognizable — and sinister — names common to growers: Bud rot and bud mold. If you're familiar with bud rot, you know it can destroy an entire crop if left untreated.

Is Bud rot systemic? ›

Botrytis is a systemic mold infection in Cannabis. This mold is often called “Bud Rot” or “grey mold”. It can remain cryptic or dormant for long periods of time before it sporulates. youPCR can be used to detect this systemic infection before it spreads to other plants.

Can you save a dead cannabis plant? ›

Essentially, the key to saving a dying cannabis plant is to keep it in as stress-free an environment as possible. Not too hot or cold, not too much moisture in the air, the appropriate amount of light, and not too much or too little water.

Does heat cause bud rot? ›

Temperature. The ideal temperature recommended for your grow varies depending on several factors, but keep in mind that bud rot prefers cooler temperatures. Most experts recommend temperatures above 68°F to keep bud rot at bay. In a greenhouse, try to avoid cold nights by using a heater.

How fast does botrytis grow? ›

The mold grows on dying and dead plant material but can also affect living cells. Usually, a Botrytis infection only becomes visible after two or three weeks.

What is the ideal temperature for bud rot? ›

When it comes to bud rot and environment, temperature is crucial. “Generally, you should aim to maintain temps above 68-70 degrees Fahrenheit, as warmer temps can help facilitate that lower humidity,” Bonelli said.

Is bud rot powdery mildew? ›

Unlike bud rot caused by Botrytis cinerea, powdery mildew can't be stopped by simply drying out the atmosphere. Many growers think of powdery mildew as a dry mold because it can spread rapidly in environments with relatively low humidity levels. This is because the devil is in the details.

Can cannabis bounce back from root rot? ›

If your entire root system has turned mushy, it is already too late. Your only option is getting rid of your crop, treating the area and starting over. If you see any firm, white and healthy roots, there is a chance you can treat the root rot to restore the health of your plants.

Should I cut off dying cannabis leaves? ›

It is important to remove damaged or dying leaves from the plant so the healthy leaves can do their job. Many cultivators choose to trim the leaves from the plants for only the first two weeks of the flowering stage to allow for appropriate bud maturation.

When should I stop giving my cannabis plants nutrients? ›

When do you stop giving cannabis nutrients? We recommend you stop feeding between days 63 and 70 of your plant's growth cycle.


1. How to Prevent Bud Rot in Cannabis Plants
(Weed In A Pot)
2. BuildASoil 10x10: HOW TO PREVENT BUD ROT: Season 2, Episode 18
3. Identifying Bud Rot on Marijuana Plants - Botrytis or Gray Mold
(Dr. Bacon Community)
4. Bud Rot and how to deal with it (Botrytis Fungus). Organic garden update & tour.
5. Bud rot on cannabis
6. What To Do With Moldy Weed


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