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Botrytis or grey mould on buds

How to get rid of botrytis or grey mould on cannabis plants?

Botrytis also known as “grey mould” is a fungal disease that affects different plants, including the cannabis plant. It is a fungus that can ruin your entire crop, whether in the growing phase, flowering or even during drying and storage.

If you want to know more about botrytis or grey mould, in our online grow shop we will explain what it is, how to prevent it, how to identify it and how to treat it to eliminate it in indoor and outdoor cannabis cultivation.

What is botrytis or grey mould?

Botrytis or grey mould is one of the most common and harmful fungi that can attack our cannabis plants, completely ruining our harvest. This fungus is a necrotrophic and parasitic fungus that feeds on living plants and dead plant debris, secreting harmful toxins that necrotize the cells.

In cannabis crops, symptoms are not observed until the disease is advanced. This will be the moment when we see the inside of our buds full of grey mould, dry leaves, brownish buds…

Botrytis or grey mould on buds
Botrytis or grey mould on buds

Why does botrytis or grey mould develop?

It is usually caused by high temperatures and high humidity. Although there are several factors that can trigger this fungus, any damage to the stem caused by; caterpillars and their waste, cut leaf petioles, dry leaves inside tight and dense buds, a too humid environment, among others, can cause the access of botrytis fungus to the plant.

As with any fungus, if it has the right conditions it will develop very quickly and in a very short time its spores will spread throughout the crop. For this reason, we must check the plants continuously, in the most hygienic way possible in order to contaminate as little as possible.

Botrytis develops in humid environments and average temperatures between 17-25ºC, which is the ideal temperature for growing cannabis. For this reason, we must make sure that the temperature and humidity parameters are correct at all times. For this we recommend using thermohygrometers at all times.

How to prevent botrytis or grey mould in cannabis

Hygiene of the growing space

To prevent the development of botrytis, first of all, we must keep the room or grow room clean at all times, if we are growing indoors. If you are growing outdoors, you should remove any fallen or dry leaves left on the ground, as the spores continue to develop in dead plant matter.

If we grow in the same place where we have suffered a fungal attack, the spores can remain in the same place and continue to reproduce. For this reason, we should clean it thoroughly with Panacure Ag Plus or bleach diluted with water.

Sterile culture accessories

In addition to the culture room or cabinet, it is a good idea to sterilise the culture accessories every time you use them. This will prevent the spores from being transported from one plant to another. It is a fungus that is transported by contaminated hands, air and tools, which is why we must sterilise them thoroughly.

Removing petioles

The petioles remaining on the branches should be removed at the same time as the damaged leaves are removed. Remember that botrytis can also develop on dead or decaying foliage.

Moisture control

Avoid crops where the relative humidity is too high. If our crop has a relative humidity higher than 60%, the probability of botrytis development increases. Therefore, we must provide constant air circulation, as well as good ventilation between plants, allowing air to circulate between them, avoiding air pockets. To maintain the temperature and humidity conditions, we must have control of the climate at all times, growth, flowering and drying.


As this fungus tends to attack the large buds, as they contain the most moisture, we can limit the risk of infection by pruning the apical buds of those plants that are most likely to suffer from it. By apical pruning, we will obtain a greater quantity of buds, however, the size of the buds will be smaller, with less humidity, avoiding excess humidity.

Use of fungicides

We can use fungicides such as trichodermas, Equiprot, which will strengthen the structural walls of the plants, preventing the penetration of the fungus into the plant, or Bio Neem, which promotes the biological defence processes of the plants.

Bio Neem de ProtecoBUY BIO NEEM

Proteco’s Botryprot is a curative/preventive product, which stops rotting of flowers and other aerial parts of the plant. Copperprot has negative effects on fungi and bacteria, acting as a curative/preventive.

Watering schedule

We can reduce the humidity of our buds by watering first thing in the morning. In this way, we will avoid an excess of humidity during the night, reducing the risk of fungal attacks.

Harvest at the right time

As this is a fungus that can affect us even after we have harvested our cannabis plants, we recommend harvesting when the plants need to be hydrated. By harvesting at this time, we will reduce the humidity inside the bud, avoiding increasing the humidity in the drying room and preventing its development. In addition, our buds will dry more quickly because they have less water to expel.

Choosing plants that are adapted to our climate

If we are aware that we may suffer from botrytis, we can choose cannabis strains that are more resistant, or faster. Sativa plants have more airy buds, through which air will pass and avoid excess humidity. In themariashop you will find sativa and fast flowering plants like Jamaican Dream, Easy Sativa, Sweet Cheese F.V. Take a look at the fastest cannabis strains. Look for plants that are harvested before the rains come, so you avoid excess moisture.

Check your plants daily, know them better than you do and treat them like queens.

Prevention and proper management of botrytis is essential to ensure a healthy and high quality cannabis plant harvest.

How to identify botrytis or grey mould?

It is actually a fungus that is very easy to detect, since at first sight a change can be seen in the affected area. It will take on a greyish colour with a fuzzy appearance, although if it is in an advanced stage it acquires a brownish colour and a dry-looking texture.

As the fungus develops, we can see the grey mould forming on the surface of the plant tissue, it takes on a greyish-white and bluish-green colour. As it progresses, the affected area begins to become necrotic, dry to the touch and crumbling.

It usually develops inside the buds, although it can affect stems, leaves, roots… We should observe the inside of the buds frequently, so that we can monitor the health of the plant at all times.

Botrytis in bud
Botrytis in bud

We must look for leaves on the buds that dry out of nowhere, for no apparent reason, dry stems, or dark brown buds that are dry.

If we find holes in the leaves, little black balls or the cause of these problems, the caterpillars, we should be alert.

Caterpillars are another enemy of cannabis that often help to create this fungus. They usually appear at the end of summer, when the buds are fully developed, devouring them completely. By eating the inside of the buds, the moisture that is created inside benefits the growth of grey mould or botrytis. With the appearance of caterpillars, they and botrytis often go hand in hand. And the damage from both is overwhelming.

Check out our blog “How to fight caterpillars on cannabis plants“.

Unfortunately, the moment we see botrytis with the naked eye, it will indicate that the fungus has penetrated the plant and the solution will be complicated.

Botrytis or powdery mildew?

Powdery mildew and Botrytis are fungal diseases that affect different plants, including cannabis.

Botrytis usually affects mainly the bud, rotting and necrotising it. In contrast to powdery mildew, which creates a white powdery coating on the leaves or stem.

If you suffer from powdery mildew visit “Products against powdery mildew on cannabis plants“.

Botrytis or grey mould problems

The main symptoms of botrytis are:

  • Formation of the fungus, in the form of greyish-white and brownish spots on buds and stems.
  • Brown spots on the stems.
  • Dryness and necrosis on buds and surrounding leaves.
Botrytis on bud, trunk and leaves
Botrytis on bud, trunk and leaves

If all the above symptoms reveal that you have suffered an attack of botrytis, we can give you a solution so that you can keep as much of your plant as possible.

What to do if my cannabis plants have botrytis?

Once we have identified a botrytis attack, we are sorry to tell you that we have already lost that area. But we must do what we can to eliminate botrytis so that it does not continue to advance and spoil our entire plant or even all the plants in our crop.

How do I get rid of botrytis or grey mould on my cannabis plants?

We are sorry to see you reading this far, because if you are still here it is because you are suffering from this dreaded fungus. As we have already mentioned, botrytis is indistinguishable and we can suffer from it at all stages of cultivation, from growth to curing.

Eliminating botrytis during growth

During the growth phase, botrytis is not a common occurrence, but it is possible. If we suffer an attack in the first weeks of cultivation, the stem of the plant will wilt because of the fungus and it can kill its vital process. However, if it is at a more advanced stage of growth, it is more difficult to suffer from wilting and will not die.

If this is the case, we recommend increasing or intensifying the hygiene of our crop.

To eliminate botrytis in growth we can use CopperProt or Botryprot.

Eliminate Botrytis in flowering

Eliminating botrytis in flowering is more difficult and harmful for the plant. As it is a fungus that causes damage to the buds, we must eliminate it completely.

We regret to inform you that the remedy to eliminate botrytis is to cut off the parts of the plant that have been affected.

Recommend using sterilised gloves and growing accessories so as not to spread the spores further. We must cut the affected area leaving a margin of at least two centimetres. This will ensure that the affected bud is completely removed.

Once we have removed all the affected parts of the plant, we must be careful not to infect the other plants in the crop. Carefully place the affected parts in a bag and dispose of them.

Bud with advanced botrytis cut off
Bud with botrytis cut off

Afterwards, we recommend sterilising the scissors used to cut the part containing the fungus. Change gloves, so that there are no spores and treat with Botryprot to paralyse the fungal growth and protect the plants from the continued development of botrytis.

Depending on the flowering period, Botryprot can be applied up to 10-15 days before harvest.

The earlier we detect it, the less area we will have affected and the less buds we will lose.

Removing botrytis after harvesting

Botrytis can appear even when our buds are drying. Poor ventilation of the drying room, or poor storage can help the fungus to develop.

Once we have suffered an attack of botrytis in flowering, we must have a very exhaustive control of humidity. The spores may have become inactive in the healthy buds and poor ventilation and excess humidity will favour their development once again.

For a good drying and curing process, and to avoid botrytis problems, you can take a look at “How to dry cannabis buds” and “How to do a good curing process”.

We are sorry to say that if you have botrytis on dried buds, the only solution is to get rid of them. Dried buds with fungus cannot recover. Therefore, it is not possible to remove botrytis from dried buds.

Consuming cannabis with fungus – botryits

The consumption of cannabis affected by fungal diseases can have serious negative effects on our health. The spores will affect the lungs and can even cause pneumonia or major respiratory problems.

Products against botrytis

  • Botryprot is a mixture of nutrients for the growth of microflora from specific micro-organism extracts. The nutrients in Botryprot have a direct effect on the fungus and prevent its development. It acts as a curative/preventive.
  • Equiprot is a basic substance based on plant extracts (horsetail) that strengthens the structural walls of the plants. It positively influences the development of all parts of the plant by exerting a biological control against fungal diseases.

Botryprot de Proteco


EquiProt de Proteco


If you are suffering from an advanced infection, we recommend mixing Botryprot with Equiprot. Botryprot will paralyse the development of the fungus, while Equiprot will dry it out.

  • CopperProt is a deficiency corrector that acts by contact and has negative effects on fungi and bacteria, acting as a curative/preventive.

Copperprot de Proteco


If we have suffered from botrytis, we already know how we can easily lose our crop completely. We advise you to prevent the appearance of botrytis at all times in order to avoid major problems. It is frustrating to spend months taking care of our crop and in the last few weeks we can lose it completely.

So prevention is better than cure and let’s enjoy our crop with good smoke.

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