How to Prevent Spider Mites In Cannabis Plants

Whether you are cultivating recreational or medical marijuana, it is inevitable for beginners to experience problems. Cannabis growing comes with lots of challenges and every grower must know how to deal with different issues. One of the major problems that any marijuana grower can face is spider mites or cannabis mites. These tiny creatures are the most damaging creatures to all species of marijuana plants.

Spider mites are tiny arachnids that are difficult to see with the human eye, however, they are quite destructive and may destroy your pot plants. This is why every marijuana grower should know the best way of dealing with these creatures to protect their plants from damage and low yield. This article will help you know more about spider mites and ways of eliminating them.

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What is a Spider Mite?

cannabis spider mites

Spider mites are minute creatures with an orangey-red color that infest most garden plants including cannabis leaves. They are arachnids that have 8 legs and no antennae just like ticks and other mites’ species. They derive their name from the way they leave silky webs on the marijuana plants they have invaded. These tiny creatures usually leave a tail of spidery webs wherever they move.

Cannabis growers must deal with a spider mite infestation quickly because they are known to spread rapidly and may affect all your plants within a short time. Spider mites reproduce very quickly, and within 8 days you will have a new population of adult size mites that will be eating up your cannabis plants. Spider mites mainly occur under conditions that are hot and dry.

Young mites measure less than a millimeter in size, making it difficult to see them with your naked eye.  Marijuana growers can easily notice an infestation because they leave behind a trail of dark dots on the leaves. As spider mites grow, they may grow to about 0.5 to 0.8 cm in size. Having a spider infestation on your cannabis garden is clearly a sign that you have a major problem that needs to be handled as soon as possible.

Spider Mites and Cannabis Plants

Spider mites love weed plants because they consume chlorophyll, a substance that all plants need for photosynthesis. These mites have tiny teeth that bite into marijuana plant cells and remove chlorophyll. If this happens from millions of mites at the same time, your entire crop will be destroyed.

Spider mites usually appear in any cannabis growing setup. However, they rarely affect hydroponic growing systems. Spider mites can destroy your cannabis plants at an incredible speed and this is why they should be eliminated within the shortest time possible.

The Life Cycle of  A Spider Mite

cannabis spider mites 4

The short lifecycle of spider mites is what makes them a resilient species. These arachnids complete the entire life cycle within a few days. When the female adult spider mite lays eggs, they usually hatch after a few days or weeks. The hatched organism is referred to as a larvae and is characterized a round body with three sets of legs and not the usual four sets.

After the egg hatches into a larva, it will feed for several days and selects a sheltered or protected spot where it can hide and molt as it enters the first nymphal stage. This nymph usually has four sets of legs and not three. The first nymph will also feed for several days and hide itself somewhere as it molds into the second nymph stage.

The second nymph will also eat for a few days, rest, and then an adult will then emerge like a spider mite butterfly ready devour your weed plants. At this adult stage, these arachnids are sexually mature and can reproduce. The male adults usually have pointy abdomens and retain the same size as the second nymph. Female mites are bigger and have rounded abdomens.

Owing to their unique life cycle, it is difficult to eradicate spider mites altogether. You may think you have eliminated them but they are still around resting as they wait to transform to the next stage.  Furthermore, an infestation can grow rapidly within a few days since adult female cannabis mites can lay about ten eggs every day. This can put your cannabis plants at an extremely high risk of being damaged.

The lifecycle of spider mites also makes it difficult for cannabis growers to tell when they are all eliminated. For example, you may eliminate all adult mites and still not know whether there are eggs or nymphs on your plants. The next colony of mites will emerge being resistant to the treatment technique you were using.  This is why cannabis growers should take a long-term treatment approach that will kill these bugs multiple times and eliminate them completely.

Signs of Spider Mites on Marijuana

cannabis spider mites

It is difficult to notice spider mites on pot leaves right away. To the naked eye, spider mites appear like small dots that are not bigger than the pencil lead tip. Most pot growers may not notice anything wrong with their plants until the infestation is big and the damage is visible to the naked eye.

This is why cannabis growers should carry out routine leaf inspections. You need to inspect both sides of pot leaves to check for spider mite damage. This should be done often, as it will allow you to act faster and get rid of these rapidly reproducing pests.

Spider Mites prefer living on the undersides of pot plant’s leaves. They tend to spin webs to help keep their colony and eggs safe. You can easily notice when spider mites are making a home beneath cannabis leaves because there will be very fine white strings on the surface. If you notice this silky webbing, it is a sign that you have a problem that should be dealt with immediately.

Pot growers can also notice fine silk on the plants’ foliage. The cannabis plants may appear dirty because the sticky silk tends to collect dirt and dust.  This is common in flowering rooms where you see buds that are covered with fine webbing.

Cannabis growers will notice the first sign of an infestation on the leaves. Tiny specks will appear on your leaves, which are little bite marks that result from biting of the plants. These tiny spots may be white or yellow in color. When a marijuana plant becomes badly infested, it will appear discolored and sickly and may eventually die.

Spider Mite Infestation

Spider mites can destroy your cannabis plants within a short time. However, the infestation usually occurs in stages. Most pot growers rarely notice an infestation until it has become too apparent and the damage to the plants is visible. A spider mite infestation on marijuana plants can be categorized into three phases:

  • An initial infestation
  • A medium-sized infestation
  • A large infestation

Initial Infestation

At this stage, you can recognize spider mites because they will leave dark dots on the leaves. These pests bite into the cannabis leaf to feed on the plant nutrients resulting in the leaves dying. Most growers are not able to notice these creatures quickly because they are extremely tiny. During the initial infestation, spider mites may nest in their white spidery webs. These silky webs are mainly found on the underside of marijuana leaves.

Medium-Sized Infestation

During medium-sized infestations, growers can notice leaves dying back because of the excessive feeding. The pot leaves will turn yellow and hang. In addition, you can easily notice a large number of white webs on the leaves. Spider mites will be destroying the buds and leaves of your cannabis plants. As a result, your plants will grow slower and the growth rate will tail off.

Large Infestation

A large infestation is quite difficult to miss. The buds and leaves of cannabis plants will be completely covered in the silky white webs. The flowering of your plants will be severely hindered and the buds will not bloom.  A large infestation of spider mites can be quite an upsetting sight because of the large white haze on your plants. When an infestation is left to thrive, it can cause the plants to die off completely.

Why are Spider Mites Dangerous for Marijuana Plants?

As a cannabis grower, there are many reasons why you should despise spider mites and protect your plants from an infestation. However, there are many treatment methods that can help you cure already infested pot plants. Here is what you should know about spider mites:

Disrupted photosynthesis-Spider mites feed on chlorophyll found within the leaves of marijuana plants. Chlorophyll is necessary for the manufacture of food or photosynthesis in plants. When spider mites destroy chlorophyll by feeding on it, the cannabis plant will gradually starve and eventually die off.  This means that a spider mite infestation can kill your cannabis plants if quick action is not taken.

Vast Appetites-spider mites have a huge appetite and they can eat up all the tender plants within a very short time. A bad infestation can even kill cannabis plants overnight. This is why you need to protect your pot plants to ensure they are not infested by spider mites.

Rapid Reproduction-spider mites are known to reproduce rapidly and can infect all your plants within a very short period of time. One mature female spider mite produces approximately one million mites within a month.  This is why you need to get rid of mites the moment you notice an infestation to protect your plants.

Webbing-spider mites tend to cover buds and leaves with a fine mesh of silky webbing and this can ruin the whole cannabis plant. This webbing tends to affect your plants even after the spider mite infestation is no longer there.

Disappearing act-spider mites tend to behave as though they are gone or killed after treatment. However, they will then reaper a few days or weeks later just after you have thought the infestation is gone for good.

Resistance-spider mites usually develop quick immunity to whatever you use to eliminate them. Therefore, if you are not quick to handle a spider mite infestation from your cannabis grow room, you may end up with lots of ‘Super-mites’ that may be difficult to eliminate. The spotted spider mites that mainly affect marijuana tend to be resistant to insecticides and have been nicknamed “the Borg” in the cannabis growing community because they are almost impossible to eliminate.

Because of their small size, spider mites can go unnoticed for a long time. Male spider mites are about 0.5mm long while females are smaller at 0.4mm long. Although they have tiny bodies, spider mites can cause massive destruction to your marijuana plants.

How to Eliminate Spider Mites on Cannabis Plants

cannabis spider mites

There are different ways that you can eliminate spider mites from your pot plants. To prevent damage and save your marijuana plants, you should start treatment as soon as you notice any sign of an infestation. If you are growing your cannabis organically, you should avoid pesticides because they are full of chemicals. The different ways of combating spider mites are as follows:

Regulating the Environmental Factors

Spider mites usually live in hot and dry conditions. Therefore, before you start any type of countermeasure against them, you should bring down the temperatures in the grow room. You can lower the temperatures to below 68ºF or 20ºC. Ensure that your cannabis plants are not damaged by the temperature changes.

You should also ensure the grow area has extra air circulation. Spider mites usually hate windy conditions and you can easily eliminate them by changing the environmental conditions of your grow room.

Pruning and Spraying

This is a technique that should be done thoroughly. Furthermore, it is time-consuming, but highly effective when eliminating spider mites. This technique involves cutting off leaves or branches that are infested by spider mites. Avoid cutting along the edge of webs or dark spots but eliminate a big part like an entire branch.

To guarantee optimal results, you should remove a huge chunk of the cannabis plant. This helps to prevent an infestation from spreading to other parts of the crop. You should then spray the plant to remove any mites that are remaining. When spraying, you should use a plant spray rather than a powerful hose.

Pruning and spraying your infected cannabis plants is an effective method. However, you will end up throwing parts of your marijuana plants. Furthermore, you need to be thorough when using this technique. Any spider mites that are left on the plant can trigger a new outbreak.

Using a Vacuum Cleaner

Another simple option for eliminating spider mites on your cannabis plant is using a handheld vacuum cleaner to suck the mites from the leaves. This technique takes time but is an effective way of getting rid of these stubborn bugs.

Ensure that the contents of the vacuum are put in a sealable plastic bag and then frozen. The mites will die because of the cold since they are used to higher temperatures. You can then get rid of the bag and its contents just like normal trash.


This is a simple and quick method of combating spider mites on your cannabis plants. However, this technique is only effective when dealing with an initial or medium-sized infestation. Put a potted garlic plant close to the stem of your marijuana plants. To release its potent smell, the garlic plant should be watered.

Additionally, several garlic cloves can be put close to the stem of your marijuana plants and water poured on them. The garlic cloves or potted garlic plants should be left in place for some time. However, you must ensure that they are removed at least 3 weeks before the end of flowering so that your cannabis does not acquire the garlic aroma.

Introducing Other Insects

The lacewings, predatory mites, and ladybirds, are an effective method of controlling spider mites on cannabis plants. These insects naturally feed on spider mites. For instance, predatory mites tend to eat all spider mites’ spores and will then eat each other after the infestation is destroyed. Lacewings and ladybirds also work in a similar manner to predatory mites.

Ladybirds eat more bugs than just the spider mites and are normally used for combating different insects. Cannabis growers can easily obtain these creatures from health shops, garden centers, and even online. You need to act swiftly when eradicating spider mites because it will take time before you completely eliminate these bugs.

To guarantee the best results, you should introduce these predatory insects when the population of mites is low. Other insects that can be used to eliminate spider mites on cannabis include:

  • Sixspotted thrips
  • Western flower thrips
  • Bigeyed bugs
  • Minute pirate bugs

Organic Insecticides or Insecticidal Soaps

The market is full of many organic insecticides that can help to eliminate spider mites from your cannabis plants. Some of the solutions that you can use include:

  • SM-90-is an organic wetting agent that has a wonderful aroma. This agent should be mixed with water and then applied to cannabis plants using a mister. SM-90 kills spider mites on contact.
  • Spinosad-this product can be applied to cannabis plants during any level of infestation and will eliminate mites on contact. You can also add them to the water supply of your pot plants to guarantee long-term protection from mites or other pests. This product will not damage your cannabis plants because it is completely organic.
  • Essentria IC3-this consists of a mixture of horticultural oils. You can use a mister to directly apply this organic spray to your pot plants. Keep in mind that the spray will be effective for 8 to 12 hours. Therefore, Essentria IC3 should be used every day or combined with other products or pest control methods.
  • NukeEm- This insecticide is new in the market and it kills spider mites eggs, larvae, and even adult stage. Furthermore, this product will not leave residues on your plant and is made from food-grade ingredients.
  • Insecticidal soaps-these soaps are perfect for spot treating of infested areas of cannabis plants. Multiple treatments are necessary because the soaps are not active for a long time. You must ensure that insecticidal soaps do not get into direct contact with your buds as they may affect their taste and potency.

Use of Natural Oils

Natural oils can also be used in combating spider mites on marijuana crops. These oils eliminate spider mites by attacking the central nervous system. Usually, a mixture of water and oil is sprayed over the weed plants. Some of the effective natural oils that kill spider plants include:

  • Rosemary oil
  • Neem oil
  • Cinnamon oil
  • Eucalyptus oil
  • Peppermint oil
  • Lemon oil

These oils are mixed with water and then applied to the marijuana plants. Since natural oils are extremely aromatic, ensure that you use a little concentration of the oils to spray your marijuana plants. This is because natural oils can infiltrate the plants and alter their taste and smell. You can also use horticultural oils such as soyabean, cottonseed, or canola oils to periodically treat your cannabis.

Never Assume Spider Mites have been completely eradicated

One problem that cannabis growers can face is the resurrection of cannabis mites after treatment. This is the worst nightmare of any marijuana grower. Spider mites lay millions of eggs and these can hatch just a few days or weeks after you are done treating your cannabis plants. When you notice a new infestation, you need to use a different method of combating these bugs and this should be done as quickly as possible.

You can also visit the local gardening center to check out the sprays they have for eliminating mites. It is always best to use these treatment techniques for a few days or weeks to ensure complete eradication of spider mites from your grow room or cannabis garden.


Just like other plants, cannabis is predisposed to garden pests that can significantly affect the ability of the plant to grow and develop. Although spider mites can be dangerous to cannabis plants, an infestation does not always translate to no harvest. The best defense is by detecting these creatures early before they reproduce rapidly and cause massive damage to your plants.

You should rotate different eradication techniques to avoid resistance to one method. In addition, you should never let your guards down even if you notice no activity of spider mites on your grow room or garden. Always remember that these arachnids reproduce rapidly and a continuous campaign will eliminate them in different stages of their lifecycle. If you are proactive about the infestation, then it is possible to deal with the problem and eradicate spider mites completely.

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Bowden draws from over a decade of home growing experience as well as consulting for small-scale and hobbyist-level growers. He has written hundreds of articles, thought pieces, and tutorials about growing cannabis at home

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