Cannabis Cultivation

Cannabis and Spider Mites in the Garden

We have beaten Thrips, Aphids, and Fungus Nat’s. The one and only bug that is almost impossible to beat are Spider Mites on Cannabis. These little bugs get in the garden and they are tough to get out it will take time and patience to get rid of, if you can at all.  It is important to understand how spider mites work in a marijuana garden to prevent as much damage before they get out of control.

What are Spider Mites?

Spider Mites are tiny little arachnids that can feed on over 200 different species of indoor and outdoor plants. They feed on these plants by sucking out the juices of the plants or tree’s leaves. Spider Mites are so small that they are almost too small to see with your own eyes. They are about 1mm in size. They have four sets of legs and an almost oval body, some mites can be translucent, green, brown, or even orange and red color. Some of these mites have two spots on their backs, these are tough to see because they are so small in size. You can use a magnifying glass to get a better look at them.

Close Up of Spider Mites On Cannabis
Close Up of Spider Mites on Cannabis

How to tell if you have Spider Mites on your Marijuana Plants?

The first thing you may notice on your cannabis plants are tiny little spots that will speckle your leaves with yellowish colour. The mites will have piercing-sucking mouths that they can use to feed on leaf tissues by extracting plant sap and fluids.

Once the Spider Mites get more out of control in the cannabis garden the grower will start to see webbing that looks sort of like a normal spider’s web, only there will be hundreds of these tiny mites living on the web. A great way to see them and if you have them is by placing a small white printer paper page under a few leaves of the plants, then give that plant a small shake and see if you get little crawling, moving dots on the paper.

This is a good sign that the plants are suffering from spider mite out break. Once the leaves are completely infested by the spider mites, they will turn brown and dull and will drop off the plant. After the mites get a foot hold on the plant, the plant will weaken and eventually die.

What are 3 tips you wish you knew when you started Growing Cannabis?

Spider Mite Leaf Damage Cannabis
Cannabis Leaf Infected By Spider Mites

How Spider Mites in your Cannabis grow room

The primary way that spider mites get into your marijuana grow room are thought the air coming into the room from the outdoors. They can get into your grow room many ways such as though the air ducts, open windows, and fans. Spider mites can also hitch a ride into your cannabis garden on you! They can get on your clothes from outside and then come in on you and rub off on your plants. Once they are in there will start to reproduce quickly in your garden.

How fast can Spider Mites take over a Marijuana Garden?

Spider Mites can reproduce very rapidly once they get into your cannabis garden. They love high temperature and dry conditions in the indoor garden. If it is between 20C – 30C in your room and under 40% humidity they will start to populate very quickly on your plants and in the room. It will only take 10 days for an adult spider mite to lay eggs, babies to hatch out, grow into an adult spider mite and then start to lay new eggs. Every single adult female spider mite can lay about 150 eggs before dying. You will not easily be able to see the eggs right away as they are on about 0.14 mm on the underside of the cannabis leaves.

Full Marijuana Plant With Spider Mites
Cannabis Plant Covered in Spider Mites

How to prevent getting Spider Mites on Cannabis plants

First you can stop them by knowing how they get in. First make sure you have a filter over every single air intake to your indoor garden, this will prevent spider mites from getting into your grow room from outside. Next make sure you are not going into outside gardens of any type or tall grass before visiting the grow room. If you do this, and then need to visit the grow room make sure to change clothes first then visit a marijuana grow room. Try to never wear outdoor clothes into a grow room without washing them first. This will go along way to keep many bad things out of your cannabis garden. If you can use a paper or lab suit when going in this is highly recommend.

Never Bring Clone Directly to the Cannabis Garden

Never bring outside cannabis clones into your garden from anyone ever! You never know what they could have on them, they could have a couple of unseen spider mites hiding under those leaves. All it will take is a few of
them to get into your grow room in may take another month for you to see them, by then it will be too late. 

Don’t bring outdoor plants to the inside grow room

Never bring outside clones into your garden from anyone ever! You never know what they could have on them, they could have a couple of unseen spider mites hiding under those leaves. All it will take is a few of them to get into your grow room in may take another month for you to see them, by then it will be too late. 

Keep your cannabis grow room clean as possible

Clean your room between crops will make sure the spider mites will have a very hard time to get established in your room if the room is always being cleaned every three months. If your room is empty for more then 14 days the remaining spider mites will die as they will have no food source to keep them thriving in the room. If you just had a bad outbreak, it may even be a good idea to use a “bug bomb” in the room between grows this will kill any mites remaining in your grow room.

Identify the mites with sticky traps

Using “Sticky Trap” in your grow room can help with catching the mites as they move around in the breeze in your grow room. You can check the traps and see what bugs the traps are catching on them.

Another way that spider mites can get into the garden is though contaminated soil or a soilless medium that you brought into the grow room. Even commercial medium could be contaminated with mites you just never know, if you purchased the garden store, there could even be spider mites on the bag itself.

What to do to keep them out before they get in?

  • Make sure you always sterilize any tools you are using in the grow room.
  • Before bring any clones into your cannabis garden always be sure to Isolate and clean every single one of them before putting them in your main garden. Once you are 100% they are clean only then bring a clone into the room. Give them one final wipe down with a cloth in order to make sure they are not eggs on the plant ready to hatch.
  • Look after the environment, spider mites love a warm, dry environment. This is why you will want to make sure you don’t give them this environment to thrive in. Keep your room a bit on the cooler side and a bit more humid will keep then from getting establish as fast and if they do get in, it will give you time to get rid of them.
  • Always watch and monitor your Cannabis plants and crop for spider mites. Look at the plants daily and look for signs of Spider Mites on the plants themselves or signs that the leaves have been attacked by the pests. The earlier you can catch them the earlier you can fight them off.

Killing Spider Mites Organically

Once you have these annoying little pests in your garden there is no need to panic. With due diligence you can get them out of your grow naturally, without using chemicals in the garden and on your marijuana plants.

Predator Mites

One of our favorite ways to get rid of spider mites is my introducing a natural predator pest of the spider mite. The predator mite once introduced to the garden will hunt down and eat the spider mites, this works extremely well in commercial cannabis growing operations. The predator mites feed on the spider mites and will not harm your plants in anyway.

Once the spider mites are gone and there is no more food for the predator mites, they will just die off in your grow room. A couple of spider mite predator mites we have used in the past include Phytoseiulus persimillis (Spidex) and Neoseiulus californicus (Spical).


Wipe the Cannabis Leaves

The first one is a great for all round control of spider mites and will quickly bring the spider mite pests under control in your grow room. The second one can be added to the grow room as a great preventative for spider mites, before they get a foot hold on the plants and the grow room.

If the spider mites have yet to get going in on your cannabis plants you can also just wipe the affected leaves of the plant down with some dish soap and some water. This is for very mild infestations though.

Using Neem Oil and Dish Soap, Water

Another great preventative is to use some neem oil or some rosemary oil with a bit of dish soap mixed into it. Then add it to a spray bottle shake it up some and then spray this mixture onto your plants. Make sure to spray all the leaves, tops and bottoms, also it is good to spray the stems and top of the soil as well just to be on the safe side.

Diatomaceous Earth Dust on Marijuana Plants

An effective dust that you can use is called diatomaceous earth, you can dust your plants with this safe pesticide making sure to do the entire plant. Diatomaceous earth will cut into the shell of the spider mites, after this happens to the pest it will dehydrate them and they will die. It will also smother the mite eggs.

Pyrethrum Usage

If you are suffering from a very bad outbreak of spider mites an excellent organic chemical to kill the mites is pyrethrum, you can use this to spray the plants and is very effective at killing the tiny mites on your plants. Use pyrethrum on your plant every couple of weeks to kill all the generations that may have hatched after the last spray.

5 Ways to Kill Spider Mites Infographic
5 Ways to Kill Spider Mites Infographic

Quarantine the effected marijuana plants

Growers may have to remove the plants out of the grow room if they are unable to remove the pest from the infected plants. If worst come to worst and you can’t get them off the plants the only option may be to kill the plants and burn them to make sure the mites are completely gone. Clean the grow room well, it would be best to wait 14 days to read plants back to the grow room. This is because spider mites can only live in the grow room for 14 days without having any food to feed on. They also only lay eggs on the underside of the cannabis leaves that you burned. This is one way to be 100% sure you have killed them off in the growing room.

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