Growing Tips

Types of pests in cannabis cultivation

We all like to have our plants big and bursting with life, right?

One of the biggest concerns a grower has is that their plants become infected with pests. This is because you are not the only one who likes cannabis, there are at least 100 organisms that feed on marijuana. 

That is why it is important to prevent this scenario, insects and / or mites that appear on our plants are generally due to poor cleaning in the growing area or environmental conditions that favor their appearance and subsequent spread.

Common pests in cannabis crops

Among the pests that can affect cannabis cultivation are insects such as spiders, mosquitoes, fungi, even mammals such as cats. The purpose of this article is to cover the most common pests that often appear on our cannabis plants and give you a way to combat them and save your crops. 

Let’s do it.

Red spider:

It is one of the most common pests. These tiny reddish mites feed on the plant, gradually weakening it.

They usually appear in environmental conditions where the following actors are present:

  • High temperature
  • Low relative humidity
  • Stuffiness
  • Periods of drought or irregular watering

It feeds on the cellular content of the leaf, absorbing them from within, and lays its eggs inside the leaf. They tend to be on the underside (back) of the leaf. The wounds left on the leaf are small white / yellow spots and a brownish discoloration around the leaf veins.

At first they will attack the lower leaves and from there they will climb to the upper leaves and the most tender shoots, decreasing the crop yield by affecting the ability of the leaf to photosynthesize.

It is common in crops under high temperatures and under humidity control, since it is a pest that develops better in these conditions. It reproduces quickly and in more advanced stages we can see cobwebs around the leaves and between the stems.


They are small insects of different colors, generally between the shades of green, yellow and black. They measure between 1 and 4 millimeters, their body is oval in shape, somewhat similar to a tick.

They are transmitters of viruses and absorb the sap, nutrients and carbohydrates of the plant, weakening it and causing stress.

Like spider mites, they appear in places with high temperatures and low humidity. Excess fertilization also encourages its propagation .

It can be seen with the naked eye on the underside of the leaves of the new shoots.

We will also notice the presence of honeydew, a kind of amber honey that aphids secrete and that mainly attracts ants, bees and wasps, as well as causing the appearance of fungi. That is why if you have ants in your crops, you should look for traces of the aphid since they usually appear and live together.

Ants play an important role in the life cycle of aphids, they absorb sap and excrete substances that they do not use such as water and carbohydrates, especially sucrose, fructose and glucose, which for an ant is a real delicacy.

The ants collect the honeydew, protect the aphid larvae from natural predators, and transport the aphids to the best places on the leaves where they can collect more sap. So they work together to survive.


They are elongated flying insects, light yellow in color. Like aphids, they feed on the plant and have a high probability of transmitting viruses to it.

They are detected with the naked eye and also leave white and yellow marks when they suck. They appear more frequently in indoor crops thanks to the high temperatures that are generated in these types of crops.

White fly:

It is another very frequent pest in marijuana crops. They are small white flying insects, no larger than 1-1.5 millimeters. They usually appear and spread in high temperature and high humidity environmental conditions.

It feeds by sucking the sap from the leaves through small bites. This weakens the plant, and if not controlled, can cause dehydration, chlorosis (yellowing) and affect its development.

Detecting them is easy, since they are visible to the naked eye. When you move the plant a little, they will fly away. In addition, you may notice small white bites on the leaves. We can also notice a kind of honeydew that they expel, which attracts other pests, such as ants and black mold. 

Its appearance and spread is related to environments with high temperatures and high humidity. In addition, when there are irregularities in fertilization, the plants weaken and are exposed to attack by this and other pests. 

Cottony Mealybug:

It has an oval shape, light gray colors and a cover that looks like cotton, hence its name. 

They are one of the largest sucking insects , so they can be seen on the leaves as well as on the most tender stems sucking the plant.

They suck the sage at high speed causing serious damage to the leaves. But in addition, they produce a sticky black molasses that we can see on stems and leaves. This molasses attracts fungi and ants.

It develops in warm and humid environments . Its appearance is associated with weak plants, diseases, stress caused by poorly performed pruning, poorly performed transplants or incorrectly separating cuttings. 

Caterpillars, snails and slugs:

They commonly appear in outdoor crops, they usually go out to eat in the evening and eat the leaves of the plants.

They are not really pests. If we are attentive by continually checking, we will be able to notice the bites and remove them manually.

Caterpillars camouflage themselves very easily and don’t usually come out during the day , so if you see a bitten leaf, I recommend checking at night with a flashlight. They like humidity so it is always good to check after a rainy day or shortly after watering.

Pest prevention and control

The main ideal is not to have to fight a pest, but to take the necessary preventive measures to prevent them from appearing in the crop. Invaders have a highly negative impact on the results we will obtain.

Among the cares we can do to prevent the appearance of pests we have:

  • Keep the grow space clean and free of weeds.
  • Reduce dust, as it is the ideal environment for mites.
  • Use preventive products and traps for pests.
  • Feed your plants correctly.
  • Avoid excess nitrogen and irregularities in fertilization.
  • Avoid drought and flooded soils.
  • Control environmental conditions such as temperature and humidity.
  • Maintain good ventilation in indoor crops or greenhouses (makes it difficult for insects to fly).
  • Check periodically.
  • In closed spaces, biological control is used with natural predators such as ladybugs (chinitas).
  • Diversify your crops; plant plants that help protect and repel pests.

Organic preventive products

In my personal opinion, preventive products are essential. The ones that have given me the best results are the ecological ones and also, they do not cause any damage to the plant. I avoid using chemical insecticides at all costs since my harvest is for personal use, and I do not want harmful chemicals for my health present in my grass.

I also have to take care of the health of my dog, Vito, who usually walks around the garden and can eat a leaf and affect him negatively.

Potassium soap with neem oil and diatomaceous earth are staples in my crops. I usually use them simultaneously in an irrigation solution for better control.

Now, let me explain the properties of each of them.

Potassium soap:

The potassium soap is a very effective insecticide, mainly consisting of water, lipids (usually oil) and potassium hydroxide or caustic potash.

Being an ecological product it does not harm plants, the environment or insects such as bees and chinitas (ladybugs). It is biodegradable and is easily absorbed by the roots as compost.

You can use it in several ways:

  • Insecticide : It works with white-bodied insects and arthropods such as aphids, spider mites and mealybugs, among others. By coming into contact with pests, it affects their outer membrane and causes them to die.
  • Cleaner : When mixed with water, it can be used to remove dust and dirt accumulated on the leaves, which in turn prevents the appearance of pests.
  • Adhesion of preventive treatments : By using potassium soap in combination with diatomaceous earth and other preventive treatments, it will help us to improve their adhesion to the leaves, thus increasing their effectiveness.

The way to apply it is by adding half a tablespoon or 10ml in a liter of water. To dissolve it easily, I recommend diluting it in a little hot water and then completing with cold water up to a liter.

To use it, you place the dissolved solution in a sprayer or atomizer, and apply it to the leaves, especially the underside. This should be done in the afternoons or in the case of indoor crops, when it is turned off so that it is absorbed at night without being directly affected by light.

It can be used throughout the vegetative stage until the first weeks of flowering.

Diatomaceous earth:

The diatomaceous earth a natural insecticide that helps prevent and control pests. Diatoms are aquatic algae that basically, when they come into contact with insects, injure them and cause them to die from dehydration.

It is a very useful organic product to control pests such as spider mites, aphids, slugs, caterpillars, whiteflies, mosquitoes, among others and at the same time totally harmless for humans and animals, in fact, it can be applied on the fur of pets to fight fleas and ticks.

This product leaves white spots on the leaves. It may not be very aesthetic, but it is very effective. It also has the property of helping to retain water in the substrate , reducing the need for such frequent irrigation. It also provides micronutrients such as calcium or magnesium, and other secondary elements, such as manganese and iron. 

To apply it you can make an infusion like a tea, then dilute 2 to 4 teaspoons of tea in a liter of water and spray on leaves, stems and substrate once a week. When used to combat pests, the amount of concentration per liter of water should be doubled.

It can also be applied dry on the substrate directly by dusting the soil with it. When preparing artisan substrates, 15-20% diatomaceous earth is usually used.

For greater effectiveness, I recommend combining diatomaceous earth with potassium soap and neem oil in the same solution. 

It can be used foliar during the vegetative period and early flowering, while in the substrate throughout the cycle. In case of blooming pests, apply only in powder or under the leaves. It is not recommended to apply on the flowers, since being a solution, it could generate excess humidity. 

Neem oil:

It is an essence extracted from the neem tree that is used as a natural repellent and insecticide, helping to prevent pests such as spider mites or aphids. It also has a fungicidal effect , thus preventing the appearance of Botrytis cinerea (gray fungus) and other harmful fungi.

It is repelled by water, this hydrophobic property is what gives it the necessary utility to repel insects in outdoor crops, since it prevents it from detaching from the leaves easily, even in rainy conditions.

It has derivatives, among which terpenes stand out, which are aromatic and volatile organic compounds. These affect insects, since their molecules are similar to the hormones of insects that control the processes of metamorphosis (Ecdysone).

Among the components that Neem oil has that most contribute to the insecticidal function we find:

  • Azadirona, Nimbolina and Vepinina: present in the oil that is extracted from the seeds.
  • Amorastaitin and Vilasinin: present in the leaves.
  • Geduninin: It is found in the oil of the seeds and the bark.
  • Nimbine and Salanine: In the leaves and seeds.

These components affect the system of insects and block the proper functioning of their real hormones, causing the insects to stop performing basic functions such as eating, mating or laying eggs.

Some insects even forget how to fly and the larvae do not move from one plant to another. Neem oil depletes the insect population until, finally, they disappear. Its effectiveness varies with respect to the species, as it works differently with each insect.

Tips for fighting pests

I particularly like to grow organically, this means that I don’t use chemical insecticides. When my plants present pests, I do not expect to eradicate them completely, instead I reduce and control the population of them so that it is a manageable situation and that it does not seriously affect my plants. Here are some of the tips that you could help yourself:

TIP1 – When I identify pests, I remove the most affected leaves to prevent further spreading.

TIP2 – At dusk or shortly before turning off the indoor light, I mix 50/50 water with alcohol and clean the leaves with a cotton ball and remove a large percentage of the plague manually.

The next day, in a sprayer I combine potassium soap with neem oil and diatomaceous earth, I apply it on the leaves during the last hours of light. The difference is that when I fight pests I use twice the concentration of the product.TIP3 – I put diatomaceous earth in the substrate as there are some pests that hide there and then climb onto the plant. 
TIP4 – When the cultivation is in mother earth, it is when they can be most affected by caterpillars or snails. For this reason, in these cases I recommend putting orange peels or potatoes under a tile (or any other similar object that simulates a cave) near the plant. 

This is because this specific pest loves dark, damp places. During the night, they will be attracted to the ” cave ” and in the morning you can easily remove them.

Snails also like beer, so you can put a glass at ground level, they will be attracted and will fall into it. Better not kill them and relocate them :)TIP5 – The whitefly is attracted to the tobacco plant , so one way to prevent them from attacking our cannabis plants is to grow tobacco in the vicinity so that they go to it. 

TIP6 – Diversify your crops. I mentioned this before, but I emphasize that by growing different plants you will improve your skills as a grower, and at the same time, you can grow plants such as mint, basil, tobacco, rosemary, thyme, lavender, coriander, parsley, rosemary and dill among many more. that can help.

TIP7 – Use  yellow traps  to catch flying insects. They are inexpensive and very useful for controlling fruit flies and whiteflies.

TIP8 – It is important to check plants frequently for early detection of pests. As long as you fight pests in the early stages of development, your plant is less likely to have long-term problems. In other words, the longer we take to react, our chances of having a good harvest will decrease.

I hope this post is useful for you, and that your plants are always healthy and strong. 

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