Spider mites are a tiny insect that will breed very quickly, and destroy your crop in a very short space of time. If you suspect that you have an infestation, then you have to act fast! So let’s not waste any time and get straight into how to get rid of spider mites on a cannabis plant.

Before you start using any pesticides, you have to be sure that the bug you are about to fight is spider mites. Having an accurate diagnosis of the problem is half way to fixing it. If you have already confirmed that you have spider mites, because you have seen their webs on your plants, it may already be too late for your crop.

How to Identify Spider Mites on a Cannabis Plant

When spider mites eat, their tiny mouths puncture cell walls in your cannabis plant leaves. They will suck out chlorophyll and other juices. This will cause small white dots to appear on your leaves.

You will see these symptoms before you see bugs. Spider mites are very hard to see with the naked eye. They also reproduce very quickly, which means if you do not act quickly, your grow room will soon be infested.

If your plants have become infested with spider mites, maybe you would have noticed webbing around your plant. This is where these mites get their names. The will produce a web, to weigh down a plant that is dying. The plant will collapse under the weight of the web, and land onto another plant.

The mites will then walk onto another plant and begin eating that one too. If not identified, and treated quickly, spider mites will kill your whole crop! It can go from one day everything being fine, to the next day everything covered in mites, be vigilant.

Get up Close

Spider mite and 3 eggs.

Try using a magnifying glass on the under sides of the leaves. With enough patience, you may be able to see a small mite. These mites can be less than a millimeter in length when fully grown.

To understand how to kill spider mites on a cannabis plant, you should understand a little about their life cycle. This will not be a one treatment job and then it’s done. To kill them all, you will need numerous treatments spaced three days apart.

If you have any questions about spider mites or any other pest, then feel free to ask for help in our cannabis growers forum

The Life Cycle of a Spider Mite

Spider mites go from their eggs to sexual maturity in a little over a week. At this point, they will be able to lay more eggs and the cycle continues.

A fully grown female spider mite will lay up to 1 million eggs in a month!! Eggs will take around three days to hatch once they have been laid.

The larva of the spider mites will start to eat your leaves and plant matter, and after a few days, will “molt” into is protonymph stage. This process continues over the next week until the spider mite has reached sexual maturity. She will breed, and lay more eggs, which will all follow the same cycle.

If not caught early, an infestation of spider mites can appear to come out of nowhere. Thousands of eggs can hatch overnight, and within a week, half those eggs, will lay thousands more eggs. If you have identified spider mites on your cannabis plant, act quickly!

Killing Spider Mites on a Cannabis Plant

Spider mites will lay eggs on the underside of the leaves, so they can be hard to get to. The adult female spider mites are the biggest threat. You have to reduce the amount of eggs being laid first, so you have to kill the females. They will be your main target.

Before you begin, remove your plants from your grow room. The grow room will need to be cleaned with disinfectants whilst the plants are not in there. Clean the grow room, and then move onto fixing the plants. No matter what method you choose to kill the spider mites, you will have to ensure your grow room is clean of any bugs too. It’s a waste of time to treat your plants, to then put them back into an infested grow room.

Pesticides for Killing Spider Mites

Pesticides can be damaging to your health, and the environment, and it is important to choose the right one for the job. Use any of these pesticides during vegetation, and early flower.

Home Made Neem Oil Pesticides

Neem oil pesticide is a very good effective and organic way to treat pests on a cannabis plant. It smells pretty bad, but it will kill and deter any bugs in your grow room. This should be part of any grow room arsenal, and should be used regularly to prevent bugs moving into your grow room.

To make a neem oil pesticide at home, follow our simple guide. This pesticide will be a good tool to have. Do not underestimate how important it is to keep up with IPM ( integrated pest management). Prevention is better than cure! Buy, and use neem oil pesticides now!

Pyrethrin Pesticides

Pyrethrins are naturally found in chrysanthemum flowers. They are a mix of six different chemicals, that are harmful to insects. Pyrethrins are commonly used to control mites, thrips, aphids, gnats, and many other pests that can be found in your grow room.

There are a lot of pesticides that contain Pyrethrins. Any of them will work. You just have to apply them correctly depending on what type of infestation you have. Routine is important. To treat spider mites, use this every 3 days, for three treatments.

Using Predatory Bugs to Kill Spider Mites

In some cases, you will contract spider mites during the flowering cycle. This is a difficult situation to be in, as you don’t want to spray your flowers with chemicals. Not only will it affect the flavour and smell of your cannabis, it could cause long term health problems if you smoke these chemicals.



Introducing beneficial insects instead of chemical pesticides is an option. The bugs are carnivorous, and will eat the eggs, larva, and adult spider mites on your plants.

Though they will not eat your plants, they will of course, produce waste and leave them on your buds. If you have a pest problem, late in flower, no matter how you treat the infestation, it is always in your best interests to wash your buds after harvest.

Use predatory bugs if there is no other option. Neem oil spray will bring you good results, and washing your buds is always an option too. Now, you have chosen your weapon. Lets get onto to treating the infestation.

Correct Pest Treatment Schedule for Spider Mites on a Cannabis Plant

Remember to clean your grow room thoroughly, before treating your plants. Don’t waste your time treating the plants to put them back into an infested room. Clean the grow room, and then treat the plants.

Keep the plants outside of the grow room, or turn off your lights if you cant remove them.

Water droplets can cause burn on the leaves of your plants. Make sure your plants are not sitting under lighting when you treat them with any foliar spray.

Spray the plants lightly, on the under side, and on top of the leaves

Don’t spray the plants so much that the leaves are dripping. A fine layer of the neem oil solution will do the trick. It is important to try and get every leaf, on the top, and the underside. The more area you can cover, the more successful this treatment will be. You can also lightly spray the top of your medium too.

Apply a light breeze over the plants, and let them dry before placing them back into the grow room

This neem oil mix can be used on flowering cannabis plants, but it is not preferable. It is not recommend to treat a cannabis plant with any pesticides within two weeks from harvest.

Whenever you spray cannabis flowers you must ensure there is a breeze flowing over the buds until they are dry. If they are wet for too long they will form mould or rot.

Repeat this treatment three times. Once, every three days!

Most pesticides will not be able to kill the eggs of spider mites. We have to treat the cannabis plant every three days as this is how long it takes for spider mites eggs to hatch.

The first treatment should kill the adults, and no more eggs should be laid. But some spider mites would have survived, and a few eggs would have hatched in the last couple of days. Treating three days after the first treatment will ensure any more mites that have hatched are killed before they reproduce.

One more treatment three days after that should see the end of the infestation.

Final notes on killing spider mites

If you are heavily into flower, then you may want to consider using the predatory bugs to kill you spider mites. Whatever method you decide to use to kill the spider mites on your cannabis plant, you will have to find out how they got in the grow room in the first place.

Remember, prevention is better than cure! Find out how they got there and make sure it doesn’t happen again! Also keep up with regular integrated pest management. If your grow room isn’t a good environment for bugs to live in, they won’t live there! Read more about IPM, and how to prevent bugs invading your grow room in our pest section. If you need any further help, as usual, you can find the whole team in the forum waiting to help you out.

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Thanks for reading! You can find more information on anything related to growing in our cannabis grow guides. All of our guides are written by experienced growers, and members of our cannabis growers forum. If you have any questions, sign up. It is free, and we are always happy to help!

Thanks for reading Percy Growers! Stay safe, don’t have bad dreams about spider mites, and happy growing!