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We will dedicate this article entirely to looking at various types of plagues that can attack our marijuana plants.

The plagues that we are going to see this time are: Botrytis, Mildew, Powdery Mildew, and Fusarium.

All of these plagues arise because of high humidity in the grow area, and their we can control them by adjusting the humidity factor.

We can use biological and chemical remedies, specifically made in order to fight each of these plagues as well as look at some of the recommendations that come with the use of these products.

Cleaning and disinfection in the grow area as well as of the materials that we use is undoubtedly the best way to prevent the emergence of all of these fungi, since they can remain dormant from one year to another, causing harm to our dear marijuana plants.



Botrytis ( Botrytis cinerea )


This pathological fungus is one of the most feared plagues for outdoor growers in many zones of Spain. In this case we can’t control the relative humidity that we have, but we can choose the plants that adapt best to our grow zones (dry zones, humid zones).

Botrytis appears in plants during the flowering phase, so we shouldn’t use any type of chemical remedy, since we run the risk of leaving traces of the product in our flowers. If we do use a chemical product during flowering, we need to keep in mind the product’s safety terms after applying the product, since if traces of the product are left behind on the buds, the marijuana could be toxic to our organism.

In order to not find ourselves in this terrible situation, we can utilize different brands that offer biological products that are made up of essential plant oils and concentrates that can be used as preventative measures.

In my opinion, good ventilation in the grow zone will help us avoid or slow down the appearance of this fungus.

We need to be attentive about cleaning areas affected by Botrytis during harvest, so that it doesn’t affect our healthy flowers.


Planta de marihuana afectada por Botrytis

Botrytis Photo: Cannabis Magazine



Powdery Mildew (Blumeria graminis)


This one is also one of the outdoor growers of this country’s most feared plagues.

It is a fungus that is characterized by first colonizing the leaves and then the flowers, creating marks of white powder. We should eliminate Powdery Mildew before it takes over a large part of the marijuana plant and we have to get rid of the whole plant.

Various phytosanitary products exist on the market that are specifically made to fight Powdery Mildew (chemical), though all of these can only be used during the growing phase.

If the plague appears during the flowering phase we can resort to the use of biological products that we find in a Grow Shop.

As is the case with all plagues, prevention is first and you can use homemade remedies such as Horsetail tea (fumigation) for this purpose.

In these circumstances I have heard that fumigating with a mixture of orange peel and water on the affected areas of the plant can fight the fungus effectively. Other growers use the same method substituting the peel for skim milk with the same results of completely eliminating the fungus.

These two homemade remedies can be applied during the flowering phase of your plants without affecting their optimal development. You should remember that if the crop in which the Powdery Mildew has appeared is indoors, you have to change the filters that you have been using, since the Powdery Mildew can be transported through ventilation.


Planta de marihuana afectada por Oídio


Mildew (Peronospora parasitica)


Mildew appears less frequently in cannabis plants but that doesn’t mean that we should ignore its effects and how to fight it.

This fungus forms in spring and develops when the humidity conditions favor it (Summer, fall).

You can recognize it by its creation of yellow toned marks on the upper portion of the leaves and whitish marks on the underside of the leaves.

The best way to stop this fungus from appearing is to avoid water stress, which aids in its emergence. Prevention through the use of horsetail tea, chamomile, nettle and elderberry (fumigation) can also be very useful.

All of these natural remedies function perfectly if the Mildew isn’t very advanced. Don’t forget that you need to treat the plants with these remedies from the beginning of their growing phase in order to guarantee effectiveness.



Fusarium (Fusarium oxysporum)


This plague really affects the cannabis plant and there are various issues that you should keep in mind in order to discourage its emergence.

In order to prevent the emergence of Fusarium you should make use of Trichoderma, a beneficial fungus which will colonize the root system therefore preventing Fusarium from colonizing it.

A damp root system can be a factor that aids in the emergence of this fungus.

You can recognize that Fusarium has set in given that once the plant is affected it starts to show withering and yellowing in the leaves, and sometimes the plant may even die.

Thank you to all of our readers this week.


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