Spider Mites and Cannabis

Spider mites have tiny sharp mouths that pierce individual plant cells and suck out the contents. This is what results in the tiny yellow, orange or white speckles you see on your plant leaves. Spider mites are common cannabis pests, especially when growing in soil. Although less common in hydroponics, spider mites can show up in any setup where cannabis is being cultivated!

Spider mites can be an especially tricky pest in the grow room. Since they are so small they can build up a big infestation before a grower even notices a single mite. Many growers see the distinctive tiny spots of a spider mite infestation and think it’s some sort of nutrient deficiency, not realizing it’s actually something far more sinister.

Spider mites are despised by growers. Here’s why…

  • Rapid reproduction – a single mature female spider mite can produce a million mites in less than a month
  • Disappearing act – spider mites often appear to be gone/killed, then they come back with a vengeance days or weeks later, right when you thought you’d gotten rid of them for good.
  • Big appetites – spider mites can eat up your tender plants in an amazingly short amount of time; a bad infestation has been known to kill plants overnight
  • Webbing – spider mites cover leaves and buds with a fine mesh of silk webbing, ruining whole crops even after you get rid of the spider mites
  • Zombie-like resistance – spider mites quickly become immune to whatever you do to try to kill them; if you don’t take care of your spider mite problem by eradicating them completely from your grow room, you may soon find you have a population of ‘Super-mites’. The two-spotted spider mite which specializes in cannabis seems to be particularly resistant to insecticides, and is sometimes referred to as “the borg” in the cannabis growing community. These ‘borg’ spider mites with two spots on their back can be almost impossible to get rid of! Read one grower’s journey to get rid of the “borg” spider mites in his grow room.

Spider mites often go unnoticed at first because they are so tiny that they look like spots to the naked eye. Male spider mites are about 1/50th of an inch long (.5mm) while females are slightly smaller at about 1/64″ (.4mm).

When spider mites attack a particular spot and you see lots of speckles near each other, the leaves may start looking yellow or bronzed. Badly attacked leaves often die prematurely. Although it starts with speckles, this pest has certainly earned the “spider” part of its name from the distinctive silk webbing they spin on vegetation, leaves and flowers once an infestation really sets in. Web-producing spider mites may completely coat the foliage and flowers with the fine silk, which collects dust and looks dirty.

Spider mites have a life cycle that helps them re-populate quickly and effectively after much of their population has been destroyed. Adult females begin the cycle by laying eggs, often on their host plants. In days or weeks an egg will hatch and become a larva, which is the first stage of life. Larvae are round bodied and have only three pairs of legs. The larvae feed for a few days, seek a sheltered spot to rest and then molt into the first nymphal stage. The first nymph now has four pairs of legs. The first nymphs feed a few days, rest and molt into the second nymph. The second nymphs feed, rest and molt into the adult stage. Overall, it can take days or weeks for spider mites to go through their whole life cycle.  Because of this variable growth process, it’s common to think that you’ve eradicated the spider mites in your grow room while they’re secretly building up numbers in one of their immature stages.

This is why it’s so important to keep treating your grow room after a spider mite infestation even if it appears that all the spider mites are gone. Just pretend they’re hiding and doing pushups, just building up their numbers for a second infestation. Treat your grow room like a war zone, and don’t allow the spider mites to build up any numbers and attack again!

 The best spider mite remedy is prevention! Early detection of spider mites is key!

Spider mites can be very quick to take over your plant, and even quicker to develop a resistance to almost any method you use to get rid of them, which is why it’s generally recommended to use multiple methods of offense against a spider mite infestation.

 

First, what type of spider mite do you have?

  • Tracked in from outside
    • Vegetable garden
    • Animals/pets
    • From a plant besides marijuana

If you have some spider mites which got tracked in randomly from outside, it’s likely you’ve got a run-of-the-mill spider mite that should be easy to get rid of. Although these guys are annoying as well, they almost seem nice compared to their cannabis-specialized counterparts. Chances are you’ll be able to successfully use one of the less harsh home remedies to stop your infestation.

  • From another marijuana garden
    • Clones were infested with spider mites
    • Tracked spider mites in from another marijuana garden
    • Any time the spider mites were living on another marijuana plant before they got to your plants

If you got your spider mites from a cannabis clone or plant from another cannabis grower, chances are you’ve got the type of spider mite that is an expert at infesting cannabis plants.

The (often two-spotted) mites often seem to be the worst spider mite in this category! These specialized spider mites are incredibly developed at living on marijuana plants, and may already be immune to many common spider mite remedies. If you believe you got your spider mites from another marijuana grower, then don’t play games. Get serious and get rid of your mites NOW, before they adapt to your grow room and become unstoppable.

 Kill Every Spider Mite You Can

Before your first treatment….Cut down their numbers!

​If it’s possible for you to bring your plants outside or somewhere safe, you might even consider spraying off as many spider mites as you can, to get their numbers down before you start your main treatments.

    • Get a fan blowing over the plants and top of growing medium Not only do plants grow better with a breeze, great air circulation is great for pest prevention. Spider mites love heat and stagnant, non-moving air. They can’t mate in windy conditions so a strong fan can help keep the infestation from getting worse. A breeze also helps pest treatments go better because fans help spray treatments dry on the plant.
    • Azamax is a time-tested way to rid your grow room of spider mites. Spray plants 15 minutes before lights out, making sure to drench the foliage under the leaves as well as the top of your soil. Use a fan to blow on your leaves to help things dry. Treat your room more than once, even if you believe the spider mites are gone. You can also add small amounts of Azamax when watering your plants, as it will not hurt your roots but will kill spider mites in the soil. You will need a mister (also called a “One-Hand Pressure Sprayer”) to spray all the leaves evenly.
      • Mighty Wash – Use just like Azamax (drench leaves top and bottom), though it works in a completely different way so you can use both of them to attack your spider mites (though not at the same time). You will need a mister (also called a “One-Hand Pressure Sprayer”) to spray all the leaves evenly.

Spinosad Products (safe & organic) – Spinosad products are organic and unlike many other spider mite pesticides, completely harmless to pets, children, and plants. Unlike many insecticides, you can spray spinosad heavily on leaves and roots with basically no negative effects. Spinosad products can be used directly to kill spider mites on contact, but can also be used when watering plants to systematically kill spider mites via the roots. Spinosad can also be effective at fighting caterpillars, thrips, and many other marijuana pests.

Can be used both as a topical spray like Azamax and Mighty Wash, and can also be used directly at the roots. Spinosad is an organic insecticide made from the fermentation of a specific soil bacteria (actinomycete Saccharopolyspora spinosa) and kills spider mites via ingestion or contact by effecting the insect’s nervous system. Spinosad can be a good choice for organic and outdoor growers, because it is very toxic to spider mites, but is less toxic to many beneficial arthropods.

Note: Most spinosad products are effective for only about 24 hours after being mixed with water, so only mix as much as you will need per application. Anything left over will be waste.

If you’ve had spider mite attack your grow room in the past, you might be unintentionally doing something to encourage or attract them.

 Keep a Clean Grow Space

Try to keep everything clean and tidy. Not only does this help prevent bugs but it protects buds so they don’t have fibers and dust all over them!

  • Make sure you have great airflow in your room because spider mites thrive in stagnant air. Creating lots of air movement will not only help prevent spider mites, fungus gnats and mold, but your plants love it too!
  • Spider mites like hot, dry weather. Maintaining a comfortable room temperature and a moderate amount of humidity in the grow room will help prevent or slow down a spider mite infestation.
  • Make sure your plants are growing in a breezy area that doesn’t get too hot – spider mites love hot weather and stagnant air. In addition to attracting pests, stagnant air can also trigger different types of mold, especially in the flowering stage!
  • If you have an air intake from outside, make sure you have some sort of filter to keep bugs from getting in
  • Collect any dead leaves or other plant matter regularly and remove them from your growing space. It doesn’t count if you put them in a neat pile or trash can in the corner, you need to keep dead plant matter out of your grow room.
  • Make sure that you or anyone who comes into your contact space is clean (don’t let anyone walk into your grow room directly from outside). Be especially cautious if the person has recently visited another grow space.
  • No dogs, cats, rabbits or any other pets in your grow space. In addition to shedding and possibly bringing in bugs, some cats will happily chew on your leaves and buds, so double reason not to let them anywhere near your plants!
  • Sprinkle Diatomaceous Earth on top of your soil and all around your grow room – this all-natural remedy is safe for humans (we can even eat it), and works because it is very jagged on the microscopic level. Tiny spider mites get ripped apart by diatomaceous earth while plants grow through it happilyMany indoor growers get spider mites from bringing in cannabis clones that are infected, or from visiting another grower or grow room with spider mites. Even just a few eggs on a clone or a few spider mites on your clothes is all it takes to start a full fledged infestation. This is the most common way people get spider mites, especially the marijuana-specialist spider mites (“the borg”) which can be almost impossible to kill!
  • Wipe up and sterilize everything in between grows.
  • Most importantly, never move plants or clones from the outside world into your grow room without treating and quarantining them. If you get a new plant, keep that plant away from your other plants until you know that it’s clean.

 

  • Dip new clones or small plants in room temperature water treated with Safer Soap, Mighty Wash or SM-90. If you can’t dip the plant, spray with a proven spider mite cure.
  • Keep new plants in quarantine for at least a week and check regularly to ensure they have no bugs before you bring them around your other plants.
  • Never go directly into the grow room from outdoors to avoid tracking in bugs. If you’ve visited another grower or grow room, it’s especially important to change your clothes and possibly shower before going to check on your plants. You don’t want to infect your plants with spider mites that are cannabis specialists!

 

If you’re growing just a small amount of marijuana for personal use and are really worried about spider mites, you might consider starting with seeds instead of clones. That way you don’t have to worry about accidentally getting cannabis zombie mites when starting from seed (plus you can choose to grow any strain you want!). Another way to help prevent some pests is to grow hydroponically, since spider mites and most pests are much less likely to thrive in a soilless environment!

Don’t Kill Beneficial Insects

  • A healthy population of predatory insects like lady bugs will help kill off pests including spider mites. The “Western Predatory Mite” is another great defense against spider mites since they specialize in killing mites.
  • Only use pesticides if you actually need them and avoid using broad-spectrum pesticides that kill lots of bugs indiscriminately. Instead, try to use narrow-spectrum pesticides that are meant to kill just the bugs you’re trying to get rid of. So for example if you have caterpillars, use something that mostly kills just caterpillars (like BT Spray which pretty much only kills things like caterpillars and fungus gnats) instead of using a pesticide that kills all kinds of bugs including caterpillars. It will not only work better to get rid of the specific pest you’re having trouble with, but it also prevents you from possibly killing some predatory insects that may be protecting your garden.
  • Don’t Kill Lady Bug Babies! These Are Beneficial to Your Garden