Common Marijuana Insects and Pests to Look Out For

Unwanted insects and other pests are some of the most annoying problems that you can encounter when growing marijuana. Unfortunately, you cannot fight them using conventional methods like using pesticides as you would with regular plants since it will make your weed unfit for consumption. 

What’s worse, some of these nasty critters can be hard to spot. The effects of some, like broad mites, may appear like a whole other problem like nutrient deficiency. Some will eat your plant before your very eyes while you watch helplessly, like the leaf miner which eats the inside of the leaf. Others may not exhibit any symptoms at all, like bud rot. leaving your plants dead and useless before you can even do anything. 

If this sounds like a nightmare to you, you should know that weed growers also have a lot in their arsenal to counter these buggers. However, the saying “an ounce of prevention is worth a pound of cure” is never the more true when dealing with marijuana pests. What you really want is to do everything so that you won’t have to deal with an infestation problem at all.

How to prevent insects and pests when growing marijuana

Marijuana pest prevention is an extensive topic which is why for our purposes, we will be focusing on how to do this for a home growing setup.

Outdoor growing

Outdoor growing setups are the most susceptible since pests can come from anywhere. It will take a lot of effort to prevent an infestation but you are not totally defenseless. Here are some popular techniques you need to learn if you are growing outdoors:

  • Diatomaceous earth – This is a fine powder made from pulverized rock that contains mostly fossilized diatoms. Diatomaceous earth is lethal to most kinds of bugs and even snails or similar pests. 
  • Companion plants – This is particularly advantageous for outdoor setups since it will benefit your whole garden in a number of ways like increasing its biodiversity, enriching the soil, and repelling certain kinds of pests. Herbs like peppermint, dill, sweet basil, chamomile, and coriander are some popular companion plants for marijuana.
  • Insect traps – These are like the sticky traps used for house files and are good for catching bigger pests. You can also use live traps for snails and slugs.
  • Using a greenhouse – If you really must grow outdoors to save on lighting costs, you can use a greenhouse to isolate your plants. This can be as small as a grow tent, or even just a makeshift structure covered with a fine net. 

These pest solutions are, of course, not limited to outdoor use. You can certainly use these as needed in case your indoor pest prevention methods fail.  

Indoor growing 

Indoor grows are not exactly impervious to a pest invasion. Even if you’ve managed to sanitize your whole grow room beforehand, there’s still a lot of ways that you can bring in pests since they are small enough to sneak into your clothing without you noticing.

  • Growing from seeds instead of clones – There is a chance that your clones or cuttings could carry a pest that may not be visible. Growing from seeds is a way to lessen the chances of carrying over a pest from a previous plant. 
  • Using a sterile growing medium and equipment – Pests and pathogens are more comfortable in soil compared to sterile growing mediums like perlite, vermiculite etc. If you really must use soil, sterilize it first by baking or steaming it. Same goes for your  equipment and tools; if it came from another grow area, sterilize it first.
  • Maintaining proper grow room atmosphere – Keeping temperature and humidity at the right levels in your grow room will make it an inhospitable environment for most pests. Younger plants often need higher temperatures similar to an outdoor environment and this deters a variety of pests and prevents mold and mildew growth. Likewise, good air circulation can also help prevent pests from settling on your plants. Some bugs find it hard to settle and reproduce when there is strong air movement around the plants. However, when using a fan, also keep in mind that it can blow any existing parasites to other plants in your grow room.

Ways to stop marijuana pests

In the unfortunate event that pests are able to bypass your preventive measures and start attacking your plants, here are some of the things you can do: 

  • Use natural pesticides – Although using traditional pesticides on marijuana is out of the question, you do have a few good organic alternatives that are just as effective and are also safe for humans and pets. Some of the most popular are:  
    • Horticultural oils – These are plant oils that are naturally toxic or act as a repellent to various pests. A popular one among marijuana growers is Neem oil and peppermint oil. There are also some products like Essentria IC3 that use a blend of these oils with other natural pesticides.  
    • Biological pesticides – These are products like Spinosad and Caterpillar BT spray which use chemicals made from bacteria. These are often also use on insecticidal soaps which weaken the outer shell of bugs.

When using natural pesticides, keep in mind that some will only be effective on certain pests. Each pesticide will also have its drawbacks, although minimal, so use them judiciously.

  • Use beneficial insects – Another good way to rid your marijuana of pests would be to bring in their natural enemies. Some examples are ladybugs, parasitic wasps, and predatory mites. Most of these insects can get rid of a variety of pests without affecting your plant and you can even order them online!

Most common marijuana pests 

Here are some of the most common insects and pests that can plague your cannabis plants, and there are quite a number of them!

Aphids

Solution: Horticultural oils (neem oil), Spinosad, insecticidal soaps, beneficial insects (ladybugs, parasitic wasps)

Often found under the leaves, aphids look like tiny oval bugs measuring a few millimeters long. They are often colored white, green, yellow, black, brown or red, depending on their stage of growth. Aphids usually suck on the leaves, leaving it with a yellow, wilted appearance.

Aphids crawling on marijuana leaves

Ants 

Solution: Powdered cinnamon, diatomaceous earth, Horticultural oils (neem oil)

Unfortunately, ants also pose a problem for marijuana plants as they tend to create nests in the soil, damaging the roots in the process. They also bring in aphids which can multiply quickly, making them doubly dangerous.

Mites 

Aleksey Gnilenkov from Moscow, Russia, CC BY 2.0 https://creativecommons.org/licenses/by/2.0, via Wikimedia Commons

Solution: Powdered cinnamon, horticultural oils, beneficial insects (parasitic wasps)

Mites are bugs that can be smaller than a millimeter, making them difficult to spot. These pests like to lay eggs and live on the underside of leaves which they suck and drain. Chances are, you’d only spot a mite infestation when it is already fully blown and the damage on your plant becomes obvious. The most common cannabis mites are:

  • Broad mites – You can often identify them from the “stipling” they make on leaves which appears like yellow dots. Once the damage gets worse, it can appear like nutrient deficiencies, heat stress or pH problems. 
  • Russet mites – Likewise, these mites can be initially identified due to the stipling on the leaves.
  • Spider mites – As its name suggests, these mites also leave a web on your plants aside from the stipling damage on the leaves.
Spider mites that likely came from my plants
Spider mites crawling on hangers

Barnacles and Scale Insects

Gilles San Martin from Namur, Belgium, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons

Solution: Pressure sprayer, beneficial insects (ladybugs), Spinosad, insecticidal soaps, horticultural oils (Essentria IC3)

As their name suggests, these insects look like scales that like to settle on a particular spot, sucking out the juices of leaves and stems. Scale insects excrete “honeydew” a liquid that attracts ants and causes sooty mold to grow on the leaves.

Molds, mildew and other fungi 

Jerzy Opioła, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

Solution: Biological fungicides, hydrogen peroxide, baking soda solution, apple cider solution, UV light, maintaining a proper environment, prevention

Molds and mildew which include Botrytis (bud rot), powdery mildew, fungus gnats (root rot) or yellow leaf spot is one of the worst problems that can strike your plants since you’ll only know that it’s there once the symptoms show. It is also practically untreatable without affecting your buds and you can only hope to prevent it from spreading by pruning the infected part and even then, buds with molds and mildew will no longer be fit for smoking or making extracts. Most fungicides are preventive and treat molds/mildews on the surface only, but there are so many kinds of bacteria and fungi that can infect your marijuana plant and unfortunately, one kind of treatment won’t necessarily address others. The best thing you can do aside from the usual preventive methods would be to install an air purifier.

Caterpillars & Inchworms

Solution: Traps, caterpillar BT spray, Horticultural oils (neem oil), beneficial insects (parasitic wasps, praying mantises)

Simply put, caterpillars will eat your plant to death. Typically they will start eating the leaves but there are others that can bore into the plant and eat it from the inside.  

Grasshoppers and crickets

Solution: Cricket traps, sticky traps, baits, beneficial insects (nematodes)

Grasshoppers can be easy to spot, you’ll probably see them munching on your plant’s leaves. Crickets are more difficult to locate since they live underground but you’ll know they’re there because of their chirping. You may also see them leave tunnels or mounds in the soil and brown spots on your plants.

Leafhoppers

Solution: Spinosad, insecticidal soaps, horticultural oils (neem oil), beneficial insects (ladybugs, lacewings)

Leafhoppers are visible with the naked eye but you may not immediately know that it is one since they come in different colors. They will munch or suck the sap out of your plant’s leaves, giving it brown or yellow spots.  

Leaf Miners

Jason Hollinger, CC BY 2.0 https://creativecommons.org/licenses/by/2.0, via Wikimedia Commons

Solution: Spinosad, sticky traps, beneficial insects (parasitic wasps)

Leaf miners literally eat the insides of your plant’s leaf, leaving visible traces on its surface. Those leaves are gone and should be pruned while you apply the treatment method of your choice.

Mealybugs

Katja Schulz from Washington, D. C., USA, CC BY 2.0 https://creativecommons.org/licenses/by/2.0, via Wikimedia Commons

Solution: Horticultural oils (neem oil, garlic oil, cinnamon oil), alcohol, pressure sprayer, beneficial insects (ladybugs)

Like scale insects, mealybugs also excrete honeydew which can cause a mold and ant problem. They also create white, cotton-like clumps on the leaves and stems.

Planthoppers

Katja Schulz from Washington, D. C., USA, CC BY 2.0 https://creativecommons.org/licenses/by/2.0, via Wikimedia Commons

Solution: Spinosad, insecticidal soaps, horticultural oils (neem oil), beneficial insects (ladybugs)

These insects suck out the moisture from your plant and leave a cotton-like growth which you may mistake for mold or mildew. 

Slugs and Snails

Solution: Traps, beneficial insects (nematodes)

While they’re easy enough to pick off, slugs and snails can easily get to your plant and leave significant damage while you’re away. The use of beer traps has a lot of growers divided since they can also attract these pests even from a distance.   

Thrips

Daiju Azuma, CC BY-SA 2.5 https://creativecommons.org/licenses/by-sa/2.5, via Wikimedia Commons

Solution: Pyrethrin, Spinosad, insecticidal soap, horticultural oils (neem oil)

Thrips can be hard to spot since adults grow to a millimeter long while nymphs, even smaller. They suck out nutrients from leaves, leaving irregular brown or silver patches. 

Whiteflies

xpda, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

Solution: Beneficial insects (ladybugs), Spinosad, insecticidal soaps, horticultural oils (Essentria IC3)

This common garden pest can easily be spotted since they congregate under the leaves where they also leave their eggs. They also suck out nutrients from the leaves, leaving white spots or killing them off completely.

Frequently Asked Questions

What’s the best way to get rid of marijuana pests?

While there isn’t a “best” way to treat a pest problem, there are a few ones that affect plants the least, like the use of beneficial insects, companion plants and diatomaceous earth. However, there will be occasions when the use of biological or natural pesticides are the only solution.

Is Spinosad safe to use on marijuana?

Spinosad is made by the soil bacterium Saccharopolyspora spinosa and is toxic to a number of known cannabis pests but its effects are negligible to humans and other mammals. Most growers would say that it does not affect the taste and smell of marijuana but should not be used a week or two before harvest.

Will Neem oil affect the taste of my marijuana?

Most growers say that it makes little to no effect on the taste of your buds, but it may cause an allergic reaction in some people. Overspraying may also clog your plant’s stomata, stunting bud growth which is why it should be used judiciously like all other pesticides.

Conclusion

It’s easy to guess the takeaway here: prevention is your best bet. However, it can also be super difficult not to bring in pests and other diseases inadvertently even if you’re really careful. There will be times when you won’t be able to avoid using pesticides, so what you need to do is identify the pest correctly so you won’t have to spray your plants with a combo of chemicals. This said, you should also check online regularly for new products since manufacturers are constantly looking for new ways to eradicate pests with little to no effect on the plant.

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