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Spider Mites


Spider mites (sometimes called spidermites) are part of the mite family and are related to ticks and other mites.

First Sign of Spider Mite Damage - Tiny Specks (Bite Marks) On Leaves

Tiny Specks - the first sign of spider mite damage on marijuana leaves

Table of Contents

Learn how to get rid of spider mites for good - this pest is a marijuana grower's worst nightmare!

Extreme Close-Up of Two-Spotted Spider Mites with Egg

Extreme close up of the two-spotted spider mite - Tetranychus urticae - a marijuana grower's worst garden pest

Growers Need to Take Spider Mites Seriously... Or This Can Happen!

Extreme spider mite damage - marijuana colas are literally covered in spider mite webs

Spider mites live on the undersides of marijuana leaves.

The first sign of a spider mite infestation is often the tiny white or yellow spots on leaves.

These tiny spots are bite marks.

Close-up of spider mite bites on a marijuana leaf

They get the "spider" part of their name from the distinctive silk webbing they spin on vegetation, leaves and flowers.

Spider mite webbing on a marijuana leaf - notice the bronze cast to the leaf - it's dying from all the tiny spider mite bites

Spider Mites and Marijuana

Spider mites are common marijuana pests, especially when growing in soil. Spider mites are less common in hydroponic setups as there is less dead organic matter, however, you can get spider mites in any setup where you're growing marijuana plants.

Spider mites are a marijuana soil grower's worst nightmare. Here's why...

Spider mites are known for:

  • Rapid reproduction (they lay millions of eggs) - one 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 when all those eggs hatch days or weeks later, right when you thought you'd gotten rid of spider mites 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
  • Webs - 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 huge population of Super mites. The two-spotted spider mite which specializes in cannabis seems to be particularly resistent to insecticides, and is sometimes referred to as "the borg" in the cannabis growing community. 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 tiny, they look like spots to the naked eye. Each spider mite is about the size of a pencil tip. Under a microscope you can see they have four pairs of legs, no antennae and a body that looks like an oval.

The spider mites with two spots on their back are often the worst for cannabis growers!

Spider mites can be an especially tricky pest in the grow room. Since they are so small they can build up quite an infestation before a grower even notices a single mite.

This cannabis leaf shows the first signs of a spider mite infestation: dozens of tiny yellow spots.

This cannabis leaf shows the first signs of spider mites - click for a closer look!
Click for a closer look

Spider mites have tiny sharp mouths that actually pierce individual plant cells and such out the contents. This results in tiny yellow, orange or white speckles on your plant leaves.

When spider mites attack a particular spot, and you see lots of speckles near each other, the leaves will often start looking yellow or bronzed. Badly attached leaves will often die prematurely, so a bad spider mite infestation can kill an entire plant.

Plants that are heavily infested with spider mites will become discolored, sickly and may even die.

Most spider mites have the ability to produce a fine silk webbing. Web producing spider mites may coat the foliage with the fine silk which collects dust and looks dirty. In a flowering room, it's common to see buds get covered in fine webbing from a spider mite infestation.

A marijuana bud covered in webbing from spider mites

Spider mites have a life cycle that helps them re-populate quickly and effectively after much of their population has been destroyed. All spider mites go through the same development stages in life.

Adult females begin the cycle by laying eggs, often on their host plants. The eggs hatch in days or weeks into the first stage, called a larva. 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.

Here are female adult spider mites with eggs
Adult female two-spotted spider mites with eggs and webbing

The males are usually the size of the second nymph and have pointed abdomens. The females have rounded abdomens and are the largest mites present.

Because of this variable growth process, it's common to think that you've erradicated 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, trying to build 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.

Solution: Early detection of spider mites, before damage is noticed, is VERY important.

Spider mites are tiny and can be detected only by a full and thorough leaf inspection (on both sides of the leaf). If you find Spider Mites you must act fast and hit them hard.

Spider mites are 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.

If you have problems with spider mites, keep a constant and varied offense for the best chance at success.

 

How To Get Rid of a Spider Mite Infestation

 

Step 1: Identify how/where you got spider mites

If you already have an infestation, you will immediately wan to start hitting them hard with something that will kill them on contact (several options are listed below). But....

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, chances are you've got a run-of-the-mill spider mite that should be easy to get rid of.

Chances are you'll be able to use one of the less harsh home remedies to stop your infestation.

  • From another marijuana grower
    • 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 marijuana grower, chances are you've got the type of spider mite that is an expert at infesting marijuana plants.

The 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 will 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.

 

Step 2: Kill Every Spider Mite That You Can Find

Now that you know what kind of mite you have, this is what you do.

Shake the plant, then kill the spider mites with something that kills them on contact, like...

Proven Spider Mite Remedies
(from serious chemical pesticides to organic repellants to home remedies)

  • 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 spidermites 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.

Azamax is a time-tested way of killing marijuana spider mites

Mighty Wash kills marijuana spider mites

  • Spinosad Products (safe & organic) - Spinosad products are organic and unlike many othe 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 is also effective at fighting caterpillers, 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 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.

Recommeded: Monterary Garden Insect Spray with Spinosad
Spinosad products are organic and kill spider mites, caterpillers and thrips

  • Doktor Doom Spider Mite Knockout Spray - This spray is hard on spider mites, but the main ingredient Pyrethrum can also be hard on plants (espcially in tight spaces without much ventilation) so use as a last resort if possible. Use with extreme care around humans as the ingredients can be toxic. Never use Pyrethrum-based products on your plants while your grow lights are on as it can burn your plants! Avoid using Pyrethrum products on young or sensitive plants as they can get burned even when the lights are left off. Do cover your grow lights and vents when bombing your plants with Pyrethrum and make sure you give the area at least 24 hours to air out before you try to breathe the air. This spray can works well for a couple of plants, but you'll want a Pyrethrum fogger if you have a lot of plants to treat. Outdoors, Pyrethrum can kill beneficial insects too, so keep that in mind if you're using natural predators to control pests (like ladybugs). All that being said, this spray will work to get rid of most spider mites, and it kills them on contact. Pyrethrum kills spider mites but not their eggs, so this product usually needs to be used 2-4 times (once every 2-3 days) to stop the breeding cycle and get rid of the toughest infestations.

No-Pest Strips kill marijuana spider mites

  • NoPest Strips - these emit a vapor that kills spider mites, do NOT use if you will be breathing air from your grow room. only get these if there will be no mammals breathing in the grow room while they're being used. These are only suitable if you're growing somewhere that is NOT your living space.

No-Pest Strips kill marijuana spider mites

  • Floramite - Strong stuff with harsh chemicals, incredibly expensive, but it often does the job when everything else fails. Use as directed and only as a last resort!

Floramite Kills Marijuana Spider Mites, but it's expensive and potentially dangerous! Use only as a last resort!

  • Bleach solution (1 tablespoon of bleach to 1 gallon of 95°F, pH balanced, water in a spray bottle) - make sure to clean all surfaces of your room, and bleach them too if possible.

  • Alcohol and Water mixed togther will also kill the bugs on contact and shouldn't hurt the plant as long as the solution contains at least 30% water.

  • SM-90 mixed with water (1 part SM-90 to 5 parts water) kills spider mites on contact and is organic (it even smells good!)

Nutrilife SM-90 kills spider mites

  • Neem Oil works in a similar way to SM-90, though Neem oil doesn't smell as nice and will leave an unpleasant taste/smell on buds when used to treat flowering plants. There's some evidence Neem oil may be harmful to humans so use with care!

  • Homemade Pepper Spray (or buy Hot Pepper Wax Spray) - make at home by mixing 9 parts water, 1 part additive-free dishwashing soap, and one tablespoon of cayanne pepper. This treatment is very effective against some types of spider mites, but is ineffective against other types.

  • Nicotine tea - hit or miss like pepper spray, but can be very effective against certain types of spider mite. Take 15 gram of organic tobacco and steep it in hot water overnight to make nicotine tea. You can also add a little bit of Safer Soap. Use like any other spider mite spray.

  • Insect predators - there are also insect predators such as lady bugs that can provide some control and reduce your spider mite numbers, but it is unlikely these will get rid of your spider mites on their own. Insect predators can be effective if you have a small problem or if you need to get to harvest and chemical sprays are not a good option.

  • Dichotomous earth - Basically, this is fossil dust - sprinkle on the top of your soil, and anywhere else in your room (window sills, doorways, etc). This powder-like substance is harmless to mammals and plants, but is incredibly sharp at the microscopic level. Therefore it will tear and dehydrate spider mites on physical contact. This will not get rid of an infestation, but can help control and slow things down when used effectively.

  • Treat Entire Grow Area With Insecticide - Treat complete room with broad spectrum insecticide (only do this for a really bad problem, or one that keeps coming back) - avoid this if you can!

Note: Many growers to avoid chemical sprays or miticides which contain Abamectin or lindane because these are harmful to humans. Please take a look at anything you use to treat your grow room, follow the directions closely, and heed all warnings. Some treatments will work for some setups or types of mites, but not for others. As mentioned earlier, if you got your spider mites from another marijuana grower, chances are you will need to resort to extreme measures to get rid of your infestation.

 

Step 3: Follow up in 2-3 days with a different method to kill them (you should also re-apply your first method)

Follow up in 2-3 days with something different that kills their eggs as well as a different method to kill the remaining adults (these ones will already be more resistant to your original method).

 

Step 4: Repeat Step 2 & 3 at least one more time - treat grow area at least once after you think spider mites are completely gone

Repeat those two step at least one more time to ensure that you have really cleaned out your grow room.

Some species of spider mite can take days or weeks to mature and will reappear in the grow room stronger than ever.

Because of this, you should treat your area at least once after you are almost certain all the spider mites are gone.

Using a mix of several different methods seems to work best for getting rid of spider mites. Some spider mites are more resistent to some methods than others.

If you can see spider mites with your eyes, it means you probably have millions in the room waiting to hatch.

 

Step 5: Prevention: thoroughly inspect and proof your grow area against future attacks

Once spider mites are gone, you need to worry about prevention.

With spider mites, the best offense is a good defense! Stop spider mites from ever getting hold of your grow room with good prevention....

 

Indoor Spider Mite Prevention

The best spider mite prevention is a clean grow room.

If you've had spider mite attack your grow room in the past, chances are you are unintentionally doing something to encourage or attract them.

There are many preventative products such as sprays or neem oil, which make plants less tasty to annoying spidermites. However, these should only be used to supplement good practices.

The most important aspect of spider mite (or any marijuana pest) prevention when growing indoors is a CLEAN GROW ROOM.

  • Never move other plants from the outside world into your grow room - this is the most common way people get spider mites, especially the marijuana specialist spider mites. If you get a clone or plant, keep that plant away from your other plants in quarantine for at least a couple weeks to ensure it has no bugs. Get a handheld microscope and use it to look for bugs on new plants, too.
  • No old dead leaves in your grow room at any time - you must collect old leaves regularly and completely 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 ever walk into your grow room directly from outside)
  • No dogs, cats, rabbits or any other pets in your grow space
  • Make sure you have good airflow in your room - spider mites like hot plants and low air movement
  • If you have an intake from outside, make sure you have some sort of filter to keep bugs from getting in
  • Dip new clones or small plants in room temperature water treated with Safer Soap and/or Neem Oil
  • Alternatively, if you're growing just a small amount of marijuana for personal use, it may be better to start with seeds than clones, since you don't have to worry about accidentally getting marijuana zombie mites when starting from seed (plus you can choose to grow any strain you want!)
  • 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 while plants grow through happily
  • Spider mites like hot, dry weather. Keeping temps cooler can help slow down a spider mite infestation
  • Keep a close watch on your plants, and react quickly at the FIRST site of spider mites!!!!

 

Outdoor Spider Mite Prevention

If you have a spider mite problem outdoors, you will want to...

  • Quarantine new plants or clones, or dip new clones in something that kills spider mites - most importantly, don't bring marijuana-specialized spider mites to your grow area!
  • Make sure there is a healthy population of predatory insects to kill off the spider mites (like lady bugs, though the "Western Predatory Mite" is your best defense against spider mites)
  • Make sure you have proper ground cover (cover your soil with a soil cover, weed barrier fabric, Diatomaceous Earth, or some other barrier). Basically, you want to prevent anything from being able to live or grow in the soil near your plants
  • If things get bad, invest in a strong pesticide that is specifically formulated for spider mites, take a look at this list for ideas, Floramite is considered a very strong and effective pesticide
  • Make sure your plants are growing in a breezy area that doesn't get too hot and stagnant - spider mites love hot weather with no breeze
  • Keep a close watch on your plants, and react quickly at the FIRST site of spider mites!!!!

 


 

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Here's a photo album of a spider mite invasion by LordLorax420
These vegetating clones were treated with Neem Oil then the entire plants were dipped in Azamax.

(Click gear icon in upper right corner to see full resolution pictures)

 

Picture: 
Default Cannabis Image - GrowWeedEasy.com
Big Symptom Picture: 
Leaf Color: 
Brown or Dark Spots
Mottling / Mosaic Pattern
Leaf Symptoms: 
Spots
Mottling / Mosaic
Slow Growth
Webbing on leaves
Plant Symptoms: 
Slow Growth
Plant Wilting / Drooping
Other Symptoms: 
Webbing
Bugs
Buds Not Fattening

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