Bugs on Cannabis Plants

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In this guide, we will cover bugs on cannabis plants. There are pictures of the most common bugs so you know what they look like. There are also pictures of what effects certain bugs have on cannabis plants so you will easily be able to identify the symptoms. 

Each bug found here will have a separate guide that goes into specific details on how to treat that particular pest. Some bugs will need a different treatment than others. 

This article is all about helping you identify which bugs may be attacking your plants. Then we can move on to the most reliable and effective way of getting rid of them.

So first off, we should begin with the most common bugs found on cannabis plants. If you already have an idea of what bug is on your plants, use the contents box to skip to the section you need.

Common Bugs Found on Cannabis Plants

There are many bugs that are common on cannabis plants. If you have found bugs on your plants, then it is most likely one of these:

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If you have bugs on your cannabis plants and you see it here, click on that bugs image to be taken to the symptoms section.

Aphids on Cannabis Plants

Aphids are small insects that suck the sap and juices out of leaves. They may also be known as greenfly or blackfly, as they can vary in colour. You should be able to spot them easily. Check on the underside of the leaves thoroughly and look for a green or black bugs that are a few millimetres in length.

Some aphids will fly too, so if you have sticky traps in your grow room, check them to see if any aphids have landed on them. In some cases, the aphid population will be small, and you may find it hard to see them. SO here are some symptoms to look out for:

Symptoms of Aphids on Cannabis Plants

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Visibly seeing aphids on your plants

Yellowing of leaves on young plants

Green bugs on the underside of leaves

Sticky sap on leaves

Signs of black sooty mould on leaves

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Spider Mites on Cannabis Plants

Spider mites are very small insects that like to live on the leaves of plants. They feed by puncturing holes in the walls of plant cells. Then they suck the juices out of them. Spider mite eggs can hatch within 3 days of being laid, and then produce eggs of its own 5 days after that. Their numbers can grow quickly. 

Because spider mites are so small and so hard to see, it is easier to identify them by the symptoms shown by the plant. Leaves will be covered in tiny white dots, and in bad cases a web will be formed on the leaves or buds of the plant.

Symptoms of Spider Mites on Plants

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Tiny white dots on cannabis leaves

Yellowing and weakness in plants

Webs being formed on leaves or buds

Red/green/black bugs on leaves

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Thrips on Cannabis Plants

Thrips on cannabis plants are one of the most common pests you will find. They are small and can range from 1-5mm in length.  In their adult stages they will have wings, but they can not fly far. They will pick up flight from a gust of wind and travel as far as they can. Then they land and look for things to eat. 

You can identify thrips by the marks they leave on the leaves of your plant. Look out for patches that look like dried spit. You will also see lots of small white uneven patches. This is where the thrips have been biting and eating the leaves.

Symptoms of Thrips on Cannabis Plants

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Visibly seeing thrips on your plants

Patches of “dry spit” on leaves

Uneven white patches on leaves

Long black flies in sticky traps

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Fungus Gnats on Cannabis Plants

Fungus gnats are small black flies that look like mosquitoes. They will often be seen walking around on the surface of soil, or on the lower parts of plants. Adult fungus gnats can be up to 8mm in length, so they are easy to spot. They may not cause a lot of damage to big plants, but can easily kill seedlings. 

The best way to identify fungus gnats is by using sticky traps. They are drawn to the yellow colour and are trapped easily. Just look out for a small black fly that looks like a mosquito. If you see those, you have fungus gnats. 

Symptoms of Fungus Gnats on Plants

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Small black flies in the grow room

Bugs that look like mosquitos

Black flies in yellow sticky traps

Yellowing leaves and sickly plant.

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Whitefly on Cannabis Plants

Whitefly are small white fly (around 2mm in length) that look like moths. They live on the underside of leaves, and are very easy to spot. Whitefly will be seen flying around the grow room. If you shake your plant gently, many of them will take flight. This makes it very easy to diagnose whiteflies on cannabis plants

The whitefly will bite into the leaves of your plants, leaving behind toxic saliva. The bites are tiny, so look out for small white dots on your leaves, much like spider mites. They also secrete honeydew, which encourages mould to grow.

Symptoms of Whitefly on Plants

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Small white flies in the grow room

Bugs that look like small moths

White flies in yellow sticky traps

Small white dots on leaves of your plants.

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Slugs and Snails on Cannabis Plants

Slugs and snails are rare on indoor cannabis plants and are more likely to be seen outdoors. Though one snail or slug will not cause a lot of damage to established plants, they can kill seedlings and small plants overnight. They will take big bites out of the leaves which can be confused with caterpillar bites.

The tell tale sign of slugs and snails will be a slimey, shiney trail that they leave behind. With the trial, and the fact that slugs and snails are reasonably big, they are easy to see, easy to find, and easy to treat if they are attacking your plants. 

Symptoms of Slugs and Snails on Plants

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A shiney trail leading to your plant

Finding snail or slugs on the plant

Big holes in lower leaves with slimey trial

Small plants eaten overnight

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Caterpillars on Cannabis Plants

Caterpillars are reasonably big bugs. The good news about that is that they are easy to see with the naked eye. The bad news is they will take big bites out of the leaves of your plants. Caterpillars will come in many different colours. Some may even have hair on them. The main thing to look out for is the damage they cause. 

You are not likely to find caterpillars in indoor grows, but they are very common on plants outdoors during spring time. Look out for big holes in leaves, with tiny black/brown balls near it. That’s the caterpillars $h*T.

Symptoms of Caterpillars on Cannabis Plants

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Visibly seeing caterpillars on the plant

Big holes in leaves all over the plant

Tiny black balls on the leaves (droppings)

Caterpillar cocoons under leaves

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Springtails on Cannabis Plants

Springtails are very small insects that live in the soil or coco of your plants. They are white and there will be hundreds of them. Springtails can often be seen after a plant has been watered. They will make their way to the top of the medium for air until the water has drained away. You may even find them in your plants run off. 

Though seeing all of these insects in your soil is scary, springtails are reasonably harmless. They will not feed on live plant matter. So your plant is completely safe. Some say they may even be beneficial.

Symptoms of Springtails on Cannabis Plants

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Tiny white insects in soil/ coco

Insects float to the top after watering

Small white insects in plants run off

Hundreds of white insects together

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Grasshoppers on Cannabis Plants

Grasshoppers will be found on cannabis plants grown outdoors and very rarely seen indoors. They are big insects and can be seen easily, and so can the holes they leave in leaves. At first there may only be a few grasshoppers, and it won’t cause many issues. But the numbers can grow quickly, and that becomes a problem. 

Look out for big holes in the leaves on your plants. Grasshoppers like to hide away on stems and branches, so look amongst them to see if you find one. They will vary in colour but will likely be green or brown.

Symptoms of Grasshoppers on Cannabis Plants

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Seeing grasshoppers on your plants

Big holes bitten in leaves

Bite marks on stems and branches

Little grasshopper on leaves

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Mealy Bugs on Cannabis Plants

Mealy bugs are a small, white, hairy insects that leaves behind a white power. This powder can often be confused with white powdery mildew. If you find signs of powdery mildew on your cannabis plants, have a good check for mealy bugs, just in case. They can be found on the underside of leaves.

In small numbers, mealy bugs will not do much damage. But they carry a lot of plant diseases. They also secrete honeydew which will encourage mould to grow. Look out for white power under your leaves. 

Symptoms of Mealy Bugs on Cannabis Plants

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Seeing white hairy bugs on leaves

White power on underside of leaves

Webbing on underside of leaves

Signs of mould or powdery mildew

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Bugs on Leaves of Cannabis Plants

Many bugs that attack cannabis plants will live on the leaves. It is the most common place to find them. Finding bugs on the leaves of a cannabis plant is the beginning of treating them. But first you have to know what bug it is, so you can treat it properly.  

This list will help you identify bugs you find on cannabis plant leaves.

Black Bugs on Cannabis Leaves

If you find black bugs on cannabis plant leaves, they will be either fungus gnats, thrips, or black aphids. Both thrips and aphids can vary in colour, sometimes they will be black. 


If you are growing outdoors, they may be ants or some kind of beetle. Both of which are unlikely to attack your plant. Make sure the black things you are seeing are bugs. They may be droppings from bigger pests like caterpillars, and grasshoppers.

White Bugs on Cannabis Leaves

Finding white bugs on cannabis leaves means you have either whitefly, spider mites or mealy bugs. You can tell which one is living on your plants, simply by looking at the size of the bug. 


White spider mites will be very small, and hard to see. Whilst mealy bugs are bigger, easier to see, and leave a white residue behind them. Whiteflies are reasonably large, and they fly. So seeing them is easy if you shake the plant to scare them.   

Red Bugs on Cannabis Leaves

Red bugs on cannabis leaves will mean one of two things, red aphids, or red spider mites. Aphids and spider mites will vary in colour, red is just another variation you may see them in.


Spider mites or aphids are both nasty pests to find on your plants. They can be hard to get rid of, and can reproduce quickly. If you have found red bugs on the leaves of your plants, treat them immediately with the appropriate pesticides.

Green Bugs on Cannabis Leaves

Finding green bugs on cannabis leaves means you either have spider mites, aphids, caterpillars or grasshoppers. Caterpillars and grasshoppers are big bugs, so they are easy to identify. 


Aphids are small but not too small, you should be able to see these with the naked eye. Spider mites however, especially green ones, can be very hard to spot. Instead look out for tiny white dots on the leaves of your plants or webs on buds. 

Flying Bugs on Cannabis Plants

Flying bugs on cannabis plants can become a problem quickly. Usually, bugs begin to fly when they are at a reproductive age. So they are looking for places to either lay eggs, and make them. Flying bugs can move from plant to plant easily. They will lay eggs wherever they land. As a result infestations can grow quickly. 

If flying bugs are found in your grow room, you need to act quickly. Figure out what bug it is, and treat accordingly. There are few different flying bugs you might find on cannabis plants. 


You can catch flying bugs in your grow room easily by using sticky yellow traps. It not only helps reduce their numbers, but it will help when it comes to identifying what bug it is too.

White Flying Bug on Cannabis Plant

White flying bugs on cannabis plants will most likely mean a whitefly infestation. The best way to tell if you have whiteflies on your cannabis plants is to gently shake it. By shaking the plant, the whitefly will get scared and take flight. You will then see them flying around the plant. 


Check on the underside of the leaves as that is where whitefly like to hide. Also check the leaves for small white dots. These are caused by the whitefly feeding on the leaves.

Green Flying Bug on Cannabis Plant

If you find green flying insects on your cannabis plants, you can be pretty sure they are aphids. Aphids are also known as green flies or black flies, and they love to live on cannabis plants. They are small but in large numbers, they can become a big problem.


Aphids also secret a liquid called honeydew which encourages mould to grow. Check sticky trap in your grow room for a green bug with small clear wings. That’s an aphid.

Black Flying Bugs on Cannabis Plants

Finding black flying bugs on cannabis plants will mean one of a few things. You either have fungus gnats, thrips or black aphids. If you have sticky traps in your grow room, check those to see if you can get a good look at the bug. That will help identify it. 


If it looks like a mosquito, it’s a fungus gnats. Thrips are thin and elongated, more like a long thin beetle. And aphids, which will look like your standard green fly, but black.

Bugs in Cannabis Plant Soil

There are many bugs that will live in the soil of your cannabis plants. Some will spend their whole lives there, some will only spend part of their life cycle there. 

You may find insect larvae living in the soil of your plants. Many insects lay their eggs in the soil too. If you do see bugs in the soil of your cannabis plants, it could be one of the following insects:


Springtails are tiny white insects that are just a couple of millimeters in length. On their own they are very hard to spot, but they come in huge numbers. Usually you will see hundreds of springtails running around the top of the soil immediately after watering the plants. 


They are not a big problem though and may even be beneficial to the plants. So don’t worry about them too much. But if you do want to get rid of them, it is very easy to do so. 

Thrip Larvae

Thrips go through many different stages throughout their life cycle. Part of their lives will be spent in the soil. It can be very difficult to tell the difference between thrip larvae and springtails. They are both very small and white. The big difference is in their numbers. 


When you have springtails, you will have hundreds, maybe even thousands of them. Thrips do not populate in huge numbers like that. Thrips are also clear, rather than white like springtails. 

Fungus Gnat Larvae

Though fungus gnats are flying insects, part of their life cycle is spent in the soil. If you find small white worms, with blackheads, you most likely have fungus gnats. At this stage, fungus gnats feed on roots, so they can cause problems if there are a lot of them. 


Fungus gnats will develop from the larvae stage, and become flying insects. They will then fly to other plants, and lay more eggs in the soil. From there the population will grow quickly.

These bugs will be found in soil, or soil like mediums. If you are running a full hydroponic setup, then you are less likely to see these bugs in your medium. But it still might happen, so stay vigilant!

Getting Rid of Bugs on Cannabis Plants

The method you use to get rid of bugs on cannabis plants will differ depending on what bug it is. Each bug mentioned here has a guide on how to kill it specifically. This way you have the most direct treatment, that is more likely to be successful. To find the guide you need, scroll up to the bug you have found in your grow room, and click the orange bar. This will take you to the tutorial on how to get rid of that specific bug.

Find the correct treatment, apply it correctly, and any bugs found on your cannabis plants will not be there for long. Any bug or pest problem can be solved, especially if you find it early! Always be on the look out the the symptoms we have explained in this post. White spots on leaves, flying bugs in the grow room, big holes in leaves. If anything looks off, come back to this guide and see if you can identify which pest it is.

Why not bookmark this page in case you need it in the future? It would be great to see you here again!

To Summarise

Finding bugs in your grow room or on your plants can be devastating. But the problem can be solved. The key to fixing it is diagnosing the bug properly, so you can treat it accordingly. You can wash your buds after harvest to remove dead bugs and debris from your plant, so they will not be lost!

Don’t panic, find the culprit, choose the most appritoe weapon, and take them down. It is much easier than you think. Just stay persistent with treatment. Of course, if you need any help with identifying bugs, or with your grow in general, you are more than welcome to join us in our cannabis growers forum. We are always happy to answer any questions you might have. See you there!

6 thoughts on “Bugs on Cannabis Plants”

  1. @macky, sorry but I didn’t see Leeches on the list. I had Leeches last grow in my RDWC. Just wonder what you might suggest I do about them little fuckers besides move? Β 
     I wanted them to taste hot lead but then common sense prevailed, luckily. 🀣 
    I just want to know how they got in my closed loop system, inspector?

  2. I lollipopped my girl today. Pulled my hand out and there was webs. I about had a coronary.Β 
    I scoped it and there were bugs. Two dead ants. It was a spider web, not spider mites. Holy shit. Adrenaline can suck.

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