How To Get Rid Of Spider Mites In The Grow Room?

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Added 29 December 2021

Spiders are total bros. They stay in their corner, mind their own business, and eat other insects. We love spiders, but it’s their long-distant cousin that we despise — the spider mite. 

While some spiders are totally harmless, spider mites can create havoc in your grow room. 

A major annoyance to every gardener worldwide, spider mites are difficult to get rid of unless you’re determined. 

Cannabis growers especially hate spider mites because the end result is terrifying. 

Simply put, spider mites can destroy your yields if you’re late. 

Prevention is better than cure for spider mites, but the problem is they are hard to spot. 

So, how do we get rid of them? This article will tell you how. 

What are these tiny crawlers, and how do you get rid of them? Let’s find out.

About Spider Mites

Spider mites on cannabis buds

Spider mites love your cannabis plants more than you do, but unlike you, they don’t share. Instead, they destroy the plant while feasting on it.

These are not your regular spiders, although they belong to the arachnid family. Once they colonize your plant, they start sucking on the plant juices, depriving the plant of them and killing it.

You can usually spot them on the underside of the leaves, where they spin webs all over the leaves and buds to protect themselves and their eggs from other predators. 

Plus, these spider mites are extremely tiny, invisible to the naked eye, and by the time you notice them, it’s already too late. And they reproduce faster than you can count — a female spider mite lays 1400 eggs a year, which hatch in a day and reproduces after five days.

 So, preventing spider mite infestation is much better than eliminating it.

Spotting Spider Mites

Spider mite on a cannabis leaf


Spider mites are pretty tricky to spot as they are tiny enough not to be seen with naked eyes. However, here are a few ways to identify them.

The easiest way to spot spider mites on your cannabis is to check the leaves closely. They suck on the plant’s sap, leaving teeth marks. So, you can use a magnifying glass or microscope to spot these teeth marks.

Another symptom of spider mites infestation on cannabis is yellow leaves. Many growers mistake this as a sign of nutrition deficiency, but it may not always be the case. Or the underside of your leaves may also look silvery or spotted with white dots due to their spiderwebs. 

Look at the leaves closely, and if you spot spider webs or holes, you need to prepare for war. Your cannabis plant may also start shedding leaves, or the leaves may have pits, which is another sign. 

Lastly, if you want to verify their presence, place a paper under the plant and shake the plant lightly — the mites slip and fall. Then, take a magnifying glass and inspect the paper — if you see something moving, it’s your friendly neighborhood spider mite. 

Preventing Spider Mites

Spider mite damaging cannabis leaves

Prevention is always better than cure, especially when it comes to our precious cannabis plants, isn’t it?

So, here are the best and safest ways to prevent spider mites in the first place:

  • Spider mites thrive in high temperatures and humidity, so keep your grow room’s temperature within 85°F or 29°C.
  • They are also good at hiding and waiting, so remove any plant debris from your grow room.
  • You can also use natural predators like ladybugs to eliminate spider mites before they start populating your cannabis plants.
  • When entering the grow room, always change clothes to avoid bringing outsiders into your cannabis kingdom.

Killing Spider Mites

Red spider mite

Prevention is better, but it’s often already too late by the time you spot spider mites on your cannabis plants. If you are at this stage, you need to use multiple ways to get rid of them.

Spider mites are notorious pests, and while you can kill them quickly, they often come back with a vengeance. So, here’s how to kill spider mites on your cannabis plants effectively.  

  • Prune Them Out

The ideal way to get rid of spider mites is to prune the infected leaves. Since these pests are too tiny, we recommend removing all the leaves with any signs of webbing or nutrient deficiencies. 

If you remove them by hand, remember to squish them to death so they don’t escape and reproduce. However, this method is effective only if the mites have just begun infesting the plants. If the infestation is severe, you will have to cut most leaves. Don’t worry — the leaves will grow back. If anything, you should be concerned that the mites may come back.  

  • Adjust the Environment

Often, adjusting the environment helps prevent spider mites in the first place. You can even get rid of them by making a few changes. For example, you can lower the temperature and humidity in your grow room to kill them. So, set your thermostat below 80°F and reduce the humidity. 

You should also increase the airflow to stop them from reproducing before they die.

  • Use Carbon Die-oxide

Another effective way to kill spider mites on cannabis is to use carbon dioxide. CO2 is harmless to your plant, but it suffocates spider mites faster than they can reproduce. 

So, seal your grow room and set the gas meter to 15,000 ppm. If you’re using a sealed chamber, set the meter to 12,000 ppm. Then, turn off the exhaust fans and turn on the CO2 generator. 

Let the generator run for an hour to suffocate spider mites. Once done, run the exhaust fan for half an hour to remove CO2 from your grow room. Finally, you can use a vacuum cleaner to pick up dead spider mites. 

To completely eliminate spider mites, repeat the entire process for at least five days. And avoid being in the grow room during this time as too much CO2 can be fatal for you. 

  • Use Organic Pesticides 

We don’t recommend using sprays or pesticides as they can harm your plant and affect your buds’ taste. They can even cause your plant nutrient burn, so they do more harm than good. However, if you have to use pesticides, only use organic ones. 

Here are a few you can try:


Spinosad is an organic pesticide that’s harmless for your plants, children, and pets. It works to eliminate many pests, including thrips, caterpillars, and spider mites. The best part of using Spinosad is that you can use it liberally, unlike other pesticides that may hurt plants in the first place. There are many horror stories of growers losing their plants to treat spider mites. Therefore be careful before you use any pesticide.

That said, you can use Spinosad even on the roots and leaves with little to no side effects. Make sure you use this product even as a preventive measure because you can simply mix it with water and water your cannabis plants as usual. This way, Spinosad works to kill the mites through the roots.

If you don't want to use the product directly on the roots, you can use it as a foliar spray.  Since Spinosad is nothing but a fermented by-product of soil bacteria, it’s harmless to you, but it kills the mites immediately on contact. Needless to say, you can use it outdoors too. On a side note, Spinosad usually works for just a day, so ensure you only mix a little for every application. If the mites remain, repeat the application after a few days.


Using Azamax is one of the most popular ways to get rid of spider mites. Almost everyone who has fought with this relentless pest has had experience with Azamax.

You can mix small amounts of this product and water your plants as usual or use it as a foliar spray. However, make sure you don't spray this on the plants when the lights are out since they tend to burn the leaves or stress them. If you don't have any other option, you can leave some fans on so the plants get dry quickly.

Azamax has a high success rate because it contains Azadirachtin — an insect growth regulator. Typically, it works by starving the pests and disrupting their growth and population. In other words, Azamax works just like synthetic commercial pesticides, sans the negative environmental impact.

Neem Oil

Many users say that neem oil is the best for cannabis plants since it’s organic and effective. However, be careful while using neem oil because excessive applications can kill the plants. From personal experience, we can tell you that abusing neem oil can kill plants quicker than spider mites!

Therefore, it's best to test before proceeding with high-strength applications. Always use half-strength of what's recommended by the manufacturer and repeat it for a few days. Then, proceed with further applications only after the plants recoup.


Sometimes, spider mites remain in the grow room no matter what you do. In such cases, your last option is to use pyrethrin products. A combination of pyrethrins and insecticidal soap tends to kill all spider mites upon contact, so it's a good option you could use as a last resort.

Pyrethrin effectively kills spider mites because it's a nerve agent that paralyzes the mites immediately. Make sure you start with small amounts before you use high-strength formulations. You can also test an unaffected area of the plant to see how the plant reacts.

You'll find various pyrethrin products on the market today so purchasing one is pretty easy. Read all the instructions from the manufacturer, so you don't harm your plants in any way. Note that although pyrethrin can kill adult pests, they do not affect the eggs and larvae, so you may have to use it frequently to ensure all the mites are gone.

And if you are using these pesticides, always turn off the lights to prevent nutrient burn. 

Summary: How to Get Rid of Spider Mites in the Grow Room

Spider mites are a nuisance, and getting rid of them is nothing sort of a small-scale war. So, gear up and be determined. You may have to sacrifice a few leaves and branches — that’s collateral damage — but do it. 

And like we mentioned early, always try to avoid spider mites in your grow room. So, use the tips shared above to ensure spider mites don’t get in your grow room in the first place.



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