Avoid marijuana’s pests and fungus

Avoid marijuana’s pests and fungus

Pour: Contributor Grow

There are many factors that can negatively affect the development of the marijuana seed. Prevention is fundamental, but if that is not enough, we have to move on to identification, control and elimination. For this, it is necessary to periodically check the plant and keep your grow weed-free to make access difficult for pests. 

We´ll divide this into two sections: Pests and Fungus


Red Spider Mite:

This pest is the most destructive of all, it can devastate entire crops in just a few days if not stopped. The climatic conditions that favor it are very high temperatures and low humidity. Normally, the mites begin by attacking the lower leaves of the plant then move towards the tender shoots. The first symptom is the appearance of small yellow spots on the top of the leaves, the sting marks caused by the spider biting into the leaves to extract the sap. The mites spread rapidly throughout the plant and in the most severe cases form webs around the buds to protect themselves.
Chemical, biological and cultural control methods can all be used to combat a red spider mite plague. For chemical control, several different active substances are recommended, each with a different mode of action to avoid resistances such as: abamectin, etoxazole, pyridaben or propargite. Apply at the recommended doses and be careful to reach well behind the leaves, as this is where the red spider mite lurks. The most widespread preventative chemical practice is to keep the soil clean by applying herbicides, whilst maintaining high humidity in the leaves of the plant and regulating the irrigation should largely prevent the presence of this plague.


This is a small white flying insect, which sits on the underside of the leaves. Its appearance is favored in conditions of high temperatures and high humidity. The bites of these insects cause the chlorosis and necrosis of the leaves, which with their sting suck the sap of the leaves, leaving larger round white marks than those of the red spider mite. This attack from white fly can then lead to black mould forming on the damaged areas. To control it place bottles of water filled with water and sweet wine or sugar along with a little pyrethrin with small holes that allow the whitefly to enter. We Specifically designed adhesive chromatic strips can also be used. A solution of 1% potash soap in distilled water can also be made. There are also a variety of popular ecological treatments such as rotenone, pyrethrins or neem.


These are a highly voracious pest of almost exclusively outdoor crops. The problem here is that they can eat whole leaves without you noticing because they take refuge inside the budding flowers. Their droppings are the cause of the botrytis fungus for which the only solution is to throw away all affected buds.

To combat caterpillars it is recommended to apply a product that repels or kill butterflies eggs and larvae, usually based on a gram-positive bacillus such as Bio Thur. There are also broad spectrum products which can control other pests , not just the caterpillars. In any case it is recommended not to apply products during the last 15 days before harvesting so that traces of products in the buds are eliminated. In all cases it is advisable to check the plants and buds after harvest and remove infected or bitten parts, as well as any live caterpillars, if there was not time to apply the product.


These are small elongated insects with greenish brown wings that hide on the underside of the leaves, feed by sucking the sap of the plants and can transmit viruses and harmful bacteria. Although they are not a very aggressive pest, the production of a crop affected by trips will be lower.

In order to prevent this pest, It should be enough to keep weed culture clean, although you could also place anti-strip adhesive strips, which will trap them. A pest of trips can be combated biologically with natural pyrethrins like Expelex, and predatory mites can also be used. The insecticide Confidor is also very effective against this pest.


If fungus appears in the grow and is not detected in time, the result could be the loss of the entire crop. Here are some recommendations that should be followed to avoid, as far as possible, the appearance of fungi:

  • Remove all plant remains 
  • Disinfect before planting and maintain proper hygiene during cultivation 
  • Check temperature and humidity 

However, even following these guides can not guarantee 100% that no fungus will appear, as spores can survive for a long time and are capable of being transported through the air. Here we will list the main fungi that can affect  cannabis plants:

Powdery Mildew:

This is a fungus that can affect both indoor and outdoor crops, and affects the aroma and flavour of the flowers. It is characterized by the appearance of white or grey powdery spots on the leaves in the initial phases, which will grow and approach the buds as the pest progresses. If the stains reach the buds the crop is pretty much ruined.

To prevent powdery mildew in indoor cultivation, you should avoid a relative humidity in the grow room of 40% and 65%. In outdoor plants keep the plants clear of dry leaves and avoiding planting in areas with few hours of sun. If cultivating in pots, it’s advisable to turn the pots so that all parts of the plants get good exposure to the sun. You should also avoid planting too many plants together to ensure good air circulation. Biological treatments for Powdery Mildew include propolis, oidioprot and ospo. The use of sulfur as a remedy in cannabis crops is not recommended, as the smell will impregnate the Marijuana. There are also chemical controls on the market such as antioid, although it is important to always take into account the safety periods recommended by manufacturers. 

Mildew (Phytophthora infestans):

Mildew symptoms closely resemble those of powdery mildew, although there are some differences that may help distinguish them.

The yellow spots usually appear on the underside of the leaves, rather than the top. Sometimes these spots are accompanied by a layer of white powder.
Once a mildew infection has been identified in your plant, it´s necessary to improve the air circulation in the crop and to prune the affected parts.

As with infections of other fungi, it is not advisable to use chemicals to treat mildew, as it leaves chemical residues that can be harmful.

Grey Mould (Botrytis):

This fungus is a necrosis process that can appear anywhere on the plant (flowers, leaves, roots, …) and is easily identified by its grey and brown appearance. This fungus spreads very quickly, so it is necessary to act quickly.
Moisture is the main cause of the appearance of this fungus, so the first step is to cut this down to below 50%. The affected parts must be cut immediately.

The biggest problem with this fungus is that it usually appears at the end of the flowering period, so it is not advised to fumigate at this time, as it would leave chemical residues. The most effective method is to cut the affected parts and harvest as soon as possible.


This term is used to refer to the different types of fungi that are in the ground.

The main symptoms are the appearance of spots and chlorosis on older leaves and stems, as well as the lignification of stems.

There are no effective treatments for this fungus, so the most sensible option is to get rid of the infected plant entirely.

From Kannabia Seed Company, as a Kannabia marijuana seeds bank, we would like to state the following items in accordance with current legislation in force in Spain:

  1. That cultivation should only be for personal supply and consumption.
  2. That the use and purpose of your cultivation must be therapeutic.
  3. That the plantation should be carried out in the privacy of your own home, similarly the  consumption.

And most importantly, all information that is given references a small cultivation. If you want to buy marijuana seeds online, we’re the best option for you.

Kannabia Seed Company vend à ses clients un produit de collection, un souvenir. Nous ne pouvons pas et ne devons pas donner de conseils de culture car notre produit n’est pas destiné à cet usage.

Nous ne sommes pas responsables de l’utilisation illicite qui pourrait être faite par des tiers des informations publiées ici. La culture du cannabis pour l’autoconsommation est une activité soumise à certaines restrictions légales qui varient d’un État à l’autre. Nous recommandons de revoir la législation en vigueur dans le pays de résidence pour éviter d’encourir l’exercice d’une activité illégale.