Quels sont les champignons qui peuvent nuire à la culture du cannabis ?

What mushrooms can harm cannabis cultivation?

16/08/22Lu en 6mn
  • A high hygrometry rate (strong humidity), accompanied by certain ambient parameters (high temperature, light, lack of air renewal) represent a set that can facilitate the presence of fungi which are harmful for the cultivation of cannabis.
  • Mushrooms make their appearance most often without warning your cannabis plants, they develop quickly and can affect your harvest significantly by generating different problems, if you cannot eliminate them in time.
  • It is necessary to show great vigilance, because the first symptoms are often hidden either in the underground part in the roots, or in a canopy whose density of leaves is too large, or even on The heads scattered on the different parts of the plant. It is important to know how to identify the fungus that attacks our cultures, but also and above all to apply the right treatment at the right time. Follow the leader !

First of all, it is good to know that the appearance of harmful fungi is not the result of chance, it can be avoided most often by applying certain preventive measures mentioned below:

The state of cleanliness of the place of culture indoors is a fundamental thing in order to avoid any unwanted appearance of possible pathogenic mushrooms. This is why we recommend carrying out an exhaustive cleaning of your cultivation space (floor, walls and ceiling), between each cycle, but also of all the tools such as equipment used, which are in direct contact of your plants.

To do this, you can use either bleach with a concentration of 5%, or using fungicides whose dilution will be adapted. Culture, make sure to maintain clean space. In order to avoid potential contamination from outside, you can change your dress to avoid contamination through spores from an outdoor place.

Regarding cultures carried out outdoors, it is much more complicated to manage this part, however, if you effectively clean your tools, this will help to drastically reduce this phenomenon.
Above all, it is necessary to evacuate and throw away from the dead leaves as well as plant waste, because it constitutes an ideal support for the growth and development of these mushrooms.

Be sure to always maintain climatic conditions (air humidity and temperature) favorable to the good evolution of each stage of culture, whether for growth or For flowering. This type of fungi manage to develop when the ambient conditions are favorable to them, that is to say when the temperature such as air humidity are high, and the renewal of the air is insufficient. If you have adequate climatic devices, so that your culture is well ventilated, that air humidity is close to 50 has 55% during flowering and that the temperature of your space is between 23 And 26 ° C, then you have no reason to worry.

For the outside, the fundamental aspect is first held in the choice of your best quality seeds in the face of this type of problem. To put it simply, if you live in a geographical region which demonstrates a high rainfall as a drop in early temperatures, you will then have to carefully select the varieties (s) to cultivate, whose flowering period must be short, to avoid the possible Attack of a fungus and to give your harvest every chance to succeed.

In case you work using clones, it is then crucial to make sure they come from a healthy mother plant. Otherwise, all of the work carried out during the prior preparation phase will be reduced to nothing, with the possibility of seeing the appearance of certain fungal problems in the short term.

    By respecting this small guide of elementary rules, you significantly reduce the conditions for their appearance. As they come from very volatile spores and which can be housed and develop in places of tiny size, one cannot guarantee their total eradication in the absolute.

    The most important thing is to know how to detect their presence early enough within the culture, so that their impact is as light as possible on each cannabis plant, by managing to eliminate them as quickly as possible to ultimately avoid accumulation Problems that would be more serious for the future of our dear harvest.

    You will discover below, which mushrooms can harm cannabis cultivation, we give you information at the same time to identify each of them precisely, as well as to actively eliminate them.


    Oïdium is certainly a fungus most common for cannabis cultivation, because it needs a temperature at least 20 ° C and high humidity to develop fully. Sudden temperature variations facilitate its growth and reproduction. It is quite easy to detect the presence of an assault by powdery mildew on a cannabis plant, the application of suitable treatment takes place easily, but you will have to know how to react before it is too late.

    As for most pathogenic fungi, it is preferable that they appear rather during the growth period than during flowering, because otherwise the heads could be contaminated and become unfit for consumption, even dangerous for your health, especially for your ways respiratory.

    How to detect the presence of powdery mildew?

    You will be able to detect that your culture is contaminated by powdery mushroom, as this fungus generally appears on leaves and the heads Cannabis plants. You will first observe scattered whitish circular tasks, powder, covering the surface of the upper part of the heads and leaves. As the propagation progresses, you will attend the number of these characteristic white tasks. In an advanced phase of evolution, the stems and the heads will be more affected.

    Oïdium treatment

    It is far from being the most difficult fungus to eliminate, however it is necessary to act in the early stages of its appearance, because if it can reach our dear high quality heads, the latter would become unfit for consumption. In order to prevent the development of this fungus, you can make an application by Foliar spraying either sulfur or copper sulphate, or a horsetail decoction, or even using baking soda, the latter being very effective and easy to prepare.

    You just have to put three rasters of baking soda in one liter of water, adding two spoons of olive oil, mixing vigorously and spray for a healing action. The use of propolis is also interesting as a preventive basis. The action of Tricoderma Harzianum which is a beneficial fungus (antagonist), neutralizes the growth and development of certain harmful fungi. We advise to introduce it when preparing your earth mixture and repotting operations.

    In the event that you want to use chemical fungicides, we recommend that you apply these with the greatest caution, especially in a confined environment indoors, because it will then be imperative to use different protective elements (cartridge mask, gloves, combination, suitable shoes, etc.) in order to preserve your health. Please scrupulously read the user manual concerning the suitable dosage, also respecting security conditions, and in particular the entry prohibition period in the contaminated culture space. An excessively affected harvest should be thrown without hesitation.


    How to identify the presence of Botrytis?

    Botrytis or gray mold, is a very common harmful fungus in the cultivation of cannabis. Fortunately, it is an easily identifiable fungus because it demonstrates a necrotic action on all the parts of the affected plants (roots, stems, leaves and heads). Its characteristic physical appearance is close to that of a cocoon of a spider, because we perceive a fairly large filamentous density And Marked with a coloring varying from brown to gray.

    The affected parts are also very dry and seem dead. The malicious side of Botrytis is that it has an incredible speed of propagation, because it can decimate all of your cannabis plants in just a few days, which is why it is necessary to act without waiting.

    Botrytis treatment

    If you want to avoid seeing the Botrytis appear on your cannabis plants, you will then have to perfectly control your indoor humidity, without ever exceeding 60% of humidity during the last four weeks of flowering, because the botrytis still appears during this period.

    In the event that this fungus demonstrates its presence with evidence, it is then necessary to start by removing and throwing all the affected parts of the plant, also including a few additional centimeters of the healthy part, preventively for your health, and to also avoid propagation on other parts of the plant or other individuals. It is preferable to avoid the consumption of the floral tops affected by the Botrytis, for the proper preservation of your respiratory tract.

    After having eliminate contaminated parts, by putting them out of the culture space, be sure to ventilate the room well to extract the volatile spores and to lower the humidity effectively, so as to obtain a air humidity close to 50 to 60 % maximum, with a ambient temperature equivalent to 26 or 27 ° C To clean up this place. If the Botrytis is suddenly present during the last days of flowering, with a rapid and unfavorable evolution indoors and outdoors, you should not procrastinate for a long time, please proceed with the harvest of your plants as soon as possible.

    If you do not have the physical means or the material means to stop the resurgence of this disastrous fungal phenomenon, then the only way to stop its progress is to permanently cut all the cannabis plants. In the case of a fairly large attack, please spray beneficial antagonistic fungi such as Trichoderma Harzianum, Ulocladium Atrum Or Gliocladium roseum directly on plants. The latter should undermine the overall development of the Botrytis. 

    We advise not to use ingredients to perform chemical treatment on botrytis plants, for the right and simple reason that these fungicidal products will leave chemical residues that are harmful to human health.

    It is easy to understand, that all fertilizers that contain important nutrients for the optimal development of our dear cannabis plants, like the phytosanitary products that we use to protect them, will find themselves in part in the plant tissues of delicious quality flowers which interest us for our own consumption. As an old adage says, it is better to warn than cure, by closely monitoring the climatic parameters concerned (temperature, humidity), just like impeccable hygiene.

    The melting of sowing or "damping off"

    The melting of sowing, also known as "Damping off" In English, is a fungal disease caused by a fungus named Pythium. The latter affects young plants from an early age, and most often when they are still only young plants or sowing. Pythium most often appears within a substrate or soil not sterilized, provided with a excessive humidity and a low ventilation.

    How to detect the melting of sowing?

    Pythium has the characteristic of affecting the bottom part cannabis plant, that is to say The lower part of the stem which is located close to the ground. The typical expression produced by this fungal disease is a significant narrowing And abnormal of the lower part of the stem, which gradually weakens until it bend it completely.

    The continuation of things is quite logical, as the plant is no longer supplied, because the transport of the sap containing the water and the nutrients is blocked in this specific location, the plant can no longer feed, which will quickly stop Its growth and gradually lead to its short -term death. Pythium is a vicious pathogen, because it can stay dormant in high quality cannabis seeds For a long time, and develop when we germinate these same seeds. 

    Treatment of the melting of sowing 

    Unfortunately, the melting of sowing which is caused directly by the presence of pythium is difficult to eliminate within a population of young plants. Quite simply, because at this stage of growth, young seedlings have a weak and fragile immune system, which will lead to their total loss in most cases.

    However, you will have to be reactive by removing the young affected subjects, located around to avoid the spread of pythium within the space. There is the possibility of applying a specific treatment, using a spray or an LSubstrate watering Using the Pythium oligandrum, which is a beneficial fungus, since he has an antagonistic action on the melting of sowing.

    Mildiou (Phytophthora infestans)

    The stump of Mildiou Phytophthora infestans acts as a fungal disease almost demonstrating the same characteristics as those of powdery mildew, With however some distinctive elements to which a certain consideration must be brought to differentiate the two phenomena.

    How to identify the presence of mildew?

    We perceive the presence of a fungal disease such as mildew, at the upper level, the upper part of the leaves and flowers, but not only, because Unlike powdery mildew, we also observe its presence and development on the lower leaves of the leaves. Primary symptoms alerting the presence of a Mildiou attack, are Small tasks of a yellowish color has translucent on the leaves, and it is also possible to observe the presence of a Thin layer of white powder similar to that of powdery mildew. But beware, because this last symptom mentioned does not necessarily appear when this disease occurs.

    Mildew treatment

    In order to gradually reduce the action of mildew and in order to completely eliminate the latter in the short term, it is necessary to cut and throw the different parties affected on the plants and to quickly evacuate them towards a recycling center, located in Good distance from the place where you make your cultures. It is also important to avoid excessively densifying your plants within your space, you must on the contrary Promote good air renewal as good ventilation in all parts of this culture habitat, to avoid seeing the mildew appear.

    An effective way to actively fight mildew is to use a treatment using a chemical fungicide product by contact like the Cymoxanil, chlorothalonil or Imazalil. It is also possible to apply a systemic chemical fungicide product such as the MyClobutanil, Metalaxyl, Fosetyl-Al, Triadimenol, Tebuconazole, or even Bitertanol.

    There Bordeaux mixture also constitutes an effective treatment against this pathogen. We recommend that we always learn about the conditions of use, such as the security measures imposed by law before any application of this type of phytosanitary product. If the progression of the disease is not stopped in time, it can easily lead to the arrival of harmful insects and a substantial loss of the total production of your cannabis plants at the same time.

    Fusarium (oxysporum)

    Fusarium is a cryptogamic disease, therefore belonging to a category bringing together an important set of filamentous mushrooms that develop in the soil or substrate. Fusarium is a saprophyte parasitic fungus, that is to say that it fits thanks to residues of other decomposition organizations. The fusarium causes the root rot And he also attacks The collar (lower part) of the stem of the plant.

    How to detect the presence of Fusarium?

    The main symptoms that we can observe during a fusarium attack are the presence of rot at the base of the stems, but also small necrotic tasks on the old leaves, as on those located on the lower part of the plant. It is also possible to see some leaves curl up upwards, before observing a gradual yellow of the latter, which will lead their fanation and then their final death. We can also detect the presence of the Fusarium, using the Lignification of stems, a good advice to ensure with certainty that plants suffer from fusariasis, is to make a transverse cut of the rod.

    If you see that the latter has a color reddish brown inside, then you will have confirmation. In any case, we perceive that the plant's immune system is weakened, because the plants have a degraded general appearance. Depending on the stage of evolution of the plant, we will witness slowed growth, or a flowering leading to a significant loss of production of significant heads. This unfavorable situation could also lead to the presence of harmful insects at the same time.

    Fusarium treatment

    If you want to avoid any fusarium attack, you will need to keep the substrate temperature below 29 c °, because Fusarium appreciates acidic soil, with a warm and dry climate. Maintain perfect hygiene conditions as much as possible, because a clean space without plant waste, will dismiss the arrival of this unwanted host in your interior garden. We advise to avoid the use of fertilizers whose concentration of nitrogen is too high, however add all the nutrients necessary for the water of your nutritive solution to meet the needs of your cannabis plants.

    You can also add between 20 and 30 cc of oxygenated water to your nutritional solution up to one application per week, as the latter contains hydrogen peroxide, which makes it possible to eradicate fusarium and improve the oxygenation of your substrate at the same time. It is also possible to add to your substrate, an antagonistic fungus such as the Trichoderma harzanium, which naturally fights and eliminates the harmful action of the Fusarium.

    Remember to ventilate the lower part of your plants as to ensure a airbag Effective in the entire space and to avoid air pockets. Be sure to spray organic fungicides such as horsetail or nettle decorations before sowing your cannabis seeds. 


    Alternaria is a cryptogamic disease which belongs to the family of Pleosporaceae, which has at least 44 spaces identified. The main cause of its presence is characterized by the decomposition of organic matter. This explains why it ravages more than 20% of agricultural crops around the world. Alternaria can cause allergy or respiratory problems in humans (bronchial asthma, rhinitis etc.). It would seem that 10 to 15% of the total population of the earth is affected by alternaria.

    How to identify the presence of alternaria?

    The signs of the appearance of a fungal disease such as alternaria, make it possible to observe Circular dry tasks of a fairly dark gray color, or brown or black, on the leaves and even on the trunk Cannabis plants. These tasks have a necrotic aspect, which will complicate photosynthesis, because the surface of capturing light by the leaves is reduced.

    The alternaria causes a gradual slowdown in the development of the plant, by considerably weakening its immune system. This usually gives the impression, that the plants suffer from poor absorption of water and nutrients, because the physical aspect of each individual suggests on a hypothetical state of deficiencies in different minerals.

    Alternary treatment

    To prevent the presence of alternaria in your cannabis culture, it is fundamental to always maintain your space as clean as possible, and above all to avoid leaving organic matter in decomposition (plant waste). It is necessary to ensure good homogeneous ventilation of space, to try to regulate Stable climatic conditions, in limiting variations as much as possible (humidity and temperature).

    Please carry out regular watering, using the right quantity water, fertilizer or nutrients necessary for the needs of your garden. Do not hesitate to apply preventive treatments using a large spectrum fungicide product. Last thing, be careful never to reuse a used substrate.