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There are hundreds of insect species that can create a plague and a threat for your marijuana plants. Above all during hot seasons like now, where they reproduce rapidly and can invade easily. Luckily, the majority that we find can be inoffensive. However, there are some that can be very damaging for our crop and so we should pay attention in order to take adequate measures to prevent and get rid of them. Some of the most common plagues that can affect our indoor or outdoor marijuana crop are: thrips, whiteflies, cochineal, aphids and leaf miners.

Watching your plants carefully is crucial for detecting any insect or anomaly before it can reproduce and turn into a plague. Many preventative remedies can be useful for different plagues so we recommend that you be cautious.


Thrips in marijuana crops


Thrips are insects with wings, between 1 and 3 mm that lay eggs on the undersides of leaves and feed on the sab. There are various types of thrips but the most common one that affects our cannabis plant is the californian thrip or occidental thrip. The females lay eggs that hatch in an environment with warm temperatures and medium humidity.


Plaga de trips en planta cannabis

Thrips. Photography by Biobest


How can we tell if we have THRIPS in our marijuana crop?


Upon sucking out nutrients, thrips leave small points and whitish marks on our cannabis plant, as if they have removed the color, on the upper parts of the leaf. If the plague is advances, you can also see wrinkled leaves, lacking in nutrients.


How do we eliminate them?


Pruning the lower parts of the marijuana plant helps to prevent them, since this is where they settle. As biological phyto-cleaners we can use natural pyrethrins or neem oil, which helps us to fight them since it makes their development difficult. Aside from that it is an antifungal agent that helps us to fight possible fungal plagues that we have seen in previous articles.

In order to make sure you notice the possible appearance of thrips in our crop, it is very common to place blue adhesive antithrip bands around the grow space which will let us know quickly if we have these insects. We can introduce the most used biological predator for getting rid of them: the ambyseius cucumeris.



Aphid in cannabis plants


There are different types of aphids and they tend to measure between 1 and 3mm. Like thrips and other insects, they feed on the sap and debilitate our marijuana plant. Another factor that doesn’t help us is that they reproduce very rapidly and in a short period of time the plague can become a strong threat. In spring and summer, the population of aphids is made of up viviparous females and their reproduction is asexual. So, they reproduce clones of the same mother, and one female can produce 100 more aphids, creating a plague from nothing. They can also transmit viruses and many other illnesses.


Plaga pulgón marihuana

Aphid plague. Photography by Biobest

How to see if you have APHIDS in your marijuana crop:


Aphids can be seen with the naked eye, as they are not microscopic. However, there are other signs that you can see. When they remove nutrients from the plant, they disrupt its growth deformation on the leaves, as well as withering can be seen.  The insect spits out excess sugar from its food creating something called honeydew. When they do this, you will notice that the leaves of the marijuana plant are sticky because of this substance, they suffer and the process of photosynthesis becomes more difficult for them.


How are they eliminated?


If you want to fight this plague with a biological predator you can get, among others, the aphidius Aphidimyza, which we recommend that you ask about in your trusted grow shop. In any case, the predator won’t be enough.

As a biological insecticide against aphids we have at our disposal: potassium soap, Neem oil or pyrethrins. There are also natural treatments available such as rotenone, nettle or garlic broth. And if you are in a desperate situation, as long as you are in a safe phase, you can use chemical insecticides with a Dimethoate component which is effective against aphids.


Leaf miners


Leaf miners feed on the photosynthetic tissue of the marijuana plant, which makes the it wither and stops its growth. They are like little diggers that create their mine on the inside of the leaf. In addition to this, when they put holes in it, they leave it vulnerable to other types of illnesses.


Plaga Minadores de hojas en planta de cannabis

Leaf Miners. Photo from LaMarihuana.com


How to see if we have LEAF MINERS in our marijuana crop:


The signs are very particular. The insect makes a hole in order to extract sap and dig tunnels through the leaf. So, we can see evidence of this on top of the leaf—curved colorless lines, with a more dull, or even whitish color.


How do we eliminate them?


These also have a respective biological predator to eliminate them: Dyglipus Isaea.

In order to fight them we can use potassium soap or Neem oil. Some growers also use a combination of both. The first thing to do is to pull off the affected leaves of the plant. As the insects travel through the interior of the leaf, they are protected, and won’t be affected when we spray any product. A good option would be to add Neem oil in the irrigation water.

Rotenone type chemicals can help us in more extreme cases, although its always advisable to avoid them certainly to make sure that your plants are far away from the flowering phase if using them.



Whiteflies in marijuana plants


The whitefly is an extremely common plague that tends to affect our indoor and outdoor crops. It sucks the sap out of the plant and leaves honeydew that makes photosynthesis difficult for the plant.


Plaga Mosca Blanca en cultivo de marihuana

Whitefly. Photograph of Biobest




How to see if we have WHITEFLIES in our marijuana crop:


You can especially see them if you move leaves, because they fly out. The first damage that you will notice is that the leaves begin taking on a yellowish tone, and dry out until they fall off. Apart from this, the honeydew gives way to a black colored mold.


How do we eliminate the whitefly?


Potassium soap and Neem oil are good options again. In this case, natural remedies that could also work for you are Tansy or Wormwood.

On the other hand, typical yellow adhesive tape can be very useful because they attract many flying insects so that you can rapidly find out which plague you have.



Cochineal in marijuana crops


This type of plague appears in warm, humid environments. We can find two types of cochineals: the normal and the cotton cushion scale kind. The latter tends to affect our marijuana plant more, above all in outdoor crops.


How to tell if we have COCHINEAL in our marijuana crop:


One can see with the naked eye how this plague attaches itself to the stalk. It leaves a trace of white wax on the stems and knots of the leaves. It also secretes excess sugar in the form of honeydew which makes the plant sticky.


How do you get rid of the cochineal?


The yellow adhesive traps work for all flying insect plagues as well as this one. If we have cochineal, we needing to remove it manually and use potassium soap.

Neem oil is also important for prevention and in order to work on the insect’s eggs. If you need to continue attacking, you can apply pyrethrum and pyrethrin.


Cochinilla algodonosa

Cotton cushion scale cochineal. Photography of Biobest



If you would like to know more about preventing other types of plagues, we suggest that you educate yourself about: the red spider mite, microscopic mites, fungus and caterpillars.