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Spider mites




Let me first start out by offering you my sympathies... mites are one of the worst pests you can encounter while growing cannabis. They can reproduce at a phenomenal rate and easily have the potential to ruin your flowering crop, nay all your plant material IF you aren't vigilant about getting rid of them.

Scared yet? You should be! Hopefully this will wake you to the seriousness of the situation; trust me you don't want to see a full blown mite infestation. Not a pretty site. That having been said, if you take care and understand the life cycle of the mites, you should be able to rid yourself of them quite easily.

The Environment.

Mites have a life cycle that varies directly with the environment... in a very hot, dry climate they can complete a life cycle in a few weeks. If the environment is cooler, and has more humidity, it can take them over a month to hatch, mature and leave their own offspring for the next wave of attacks on your plants.

This is very important to understand, because it's easier to destroy the population if there aren't new ones popping up as fast as you can kill them.

So your first goal is to make the environment less hospitable for the evils... drop the temps as low as possible, and increase the humidity in your grow chambers. An evaporative cooler should help.... this can be as simple as a bucket with a fan pointing across the water. Stale air is a no no as well, so get some good fans constantly blowing across your plants (making it very difficult for mites to lay their eggs) and increase the ventilation if possible... depending on your setup, this should also help drop the temps, but may decrease overall humidity.

Biological Controls.

You can go bio and use predatory mites. Phytoseiulus persimillis is a voracious mite that feeds on the evil mites, but won't eat your plants. When they've eaten all the mites they can find, they run out of food and die.

If you choose to go this route, use one of the chemical sprays mentioned below (to knock down the spotted mite population), but discontinue it's use a week before introducing the predators; which are themselves susceptible to the chemical sprays.

*Studies have shown that mites were able to elude the persimillis by hiding in various nooks and crannies around the garden, only to return to and take over again when all the predators had died.

IF you do use predators, a time-release is recommended... add another dose to your plants each week for a month just to make sure you've got some fresh predators to hunt down any re-occurring mites that have been missed. The predator mites will eat all life stages of evil mite, from egg to adult. Adding predators can get expensive; only the truly organic tend to use this route.

Check online to find a cheap source of predators; a Google search for "predatory spider mites Phytoseiulus persimillis" should yield numerous places to purchase.

Environmental considerations for predator mites.

The environment plays a big role in biological predator mite control. In general, ?evil? mites prefer a HOT + DRY climate; the predators prefer a COLD + HUMID climate.

If you put the preds in a hot dry climate, the evil mites will out reproduce them, and the predators won't reproduce fast enough to kill them all. Same opposite for a colder/humid room... the predators will easily out reproduce the evils, and will have a much easier time of taking care of the problem.

Introducing predators to a flowering (12/12 light cycle) chamber is essentially futile according to leading cannabis researchers... the predators seem to just go to sleep. They are more suited to the longer light cycle in a veg room.

Chemical sprays.

Spraying daily with water is really hinders the spotted mite's reproduction.

There are many sprays that will kill spider mites. Kelthane, Malathion, Neem oil, pyrethrum based sprays.... the list goes on and on.

There is a product called AVID which is sold illegally under the counter in many hydro stores. AVID is similar to a systemic; it is translaminar. The safety of AVID in cannabis and breakdown periods in leaf tissue have never been shown adequately IMO, so I don't use it nor recommend its use to anyone. NEVER use AVID in flowering, if you feel you need to use it at all.

I've had great results using the 'softer' pyrethrum based products. Pyrethrum is a natural miticide produced by flowers in the chrysanthemum family, it works against all the different mite populations. Repeated treatment is key; most of the sprays are unable to penetrate to the eggs; so you need to re-apply the spray to take care of the hatched eggs before they have a chance to lay more eggs themselves.

Spray application.

Get yourself a quality pressure sprayer (a separate container and a wand type are the best) at home depot or Canadian Tire etc. The wand allows you to easily get under the leaves where the mites spend most of their time sucking the juices from your babies.

I highly recommend floramite (see link below).

Spray tips.

Always read the label for mixing direction, and never spray closer to harvest than recommended by the manufacturer (Never use a product recommended for ornamentals only... make sure it is safe for use on food crops.).

These types of sprays are contact sprays... if the solution doesn't come into contact with the pest, the pest won't die!! This is why it is so important to use a good sprayer and make sure you coat the entire plant- top and bottom of the leaves. Even spray the surface of the medium.
The mites MUST come into contact with the spray o be killed. Mite eggs are resistant and won't be destroyed, so you'll need to reapply the spray the before the hatched eggs can lay their own eggs.

Other homemade chemicals.

If you smoke cigarettes, you can also make a spray with a small amount of dish soap, and some tobacco. The nicotine is extremely toxic, and will kill the bugs if they come in contact with it. Break a bunch of cigarettes up and soak the tobacco in water overnight. Beware of the possibility of TMV (tobacco mosaic virus), unless you boil your solution for ~20 minutes (after adding the tobacco) to kill the virus. Let cool, add your few drops of detergent and voila. Strain it, spray it.

You can also add some types of hot pepper powder (cayenne etc), or if you have access to chrysanthemums... get a bunch, remove all the petals and blend them in a blender with water. Strain, and add to your soapy solution. This should work also.

Room sterilization and other tips.

Bug bomb your rooms (Dr Doom etc) between crops, or whenever you can get the plants out, if possible.

It is also very important to clean out your growth chambers.
I've used a second pressure sprayer filled with a strong bleach/water mix... the hotter the water the better. Remove all your plants from the room (After first spraying with endall- you don't want to bring bugs out of the chamber) and completely soak the chamber in the bleach/water spray. Get all the walls, the entire floor and don't forget the cracks in the walls or the base of the trim. Allow this to air dry. Repeat if possible. Spray the plants down again with your Endall solution before you put them back in, just in case you missed a few the first spray.

Don?t introduce mites to your room! Check other houseplants for mites, and treat them as well if infected. Pets should not be allowed into the garden, especially if they are outdoor pets. Same goes for you... change your clothes and shoes before working on you garden, and never use the same tools as you use for your outdoor veggies or houseplants.

Be particularly careful about changing your clothes/shoes if you've been walking in the woods, have been to a nursery or a garden store/ hydro store. You don't want to bring someone else's problem home on your clothes and introduce it to you garden!

The best product in my opinion for mites is FLORAMITE.

http://www.cdms.net/ldat/ld5GE007.pdf <<<<<<<

Spider mites are a common pest to be found feasting upon our lovely marijuana plants. They flourish in warm (greater than 85°F) and dry (less than 60% rH) environments, generally living on the underside of a plant's leaves and causing damage by puncturing the plant cells in order to feed upon the vital life juices inside! These evil doers can make quick work of a crop with their short generational cycle (about one week in between hatchings and one more week for the mite to reach adulthood), and should therefore be dealt with as soon as possible in order to avoid serious damage, including the potential death of your plants.

Prevention is better than the cure!
It is always better to prevent an infestation by practicing clean growing techniques.

•Sterilize your indoor grow room prior to growing (and in between harvests) with a dilute bleach solution.
•Keep things clean by removing dead plant material or other organic material from your grow space.
•Keep your indoor cultivation tools separate from your outdoor tools.
•Do not enter your indoor garden after having worked in your outdoor garden.
•Keep pets out of your grow area, wash hands and wear clean clothes whenever entering the grow area.
•If possible, use a closed grow room with a HEPA filter installed on the incoming air duct.
•In essence, just do everything you can to keep the grow environment (including yourself) clean and contaminant free!

Signs of Spider Mites.

Know what to look for when diagnosing the early stages of a spider mite infestation.

•Small (pin point) yellow or brown dots on the leaves of the plant.
•Very small strands of silk webbing on the plant, particularly underneath the leaves.
•Small (pin point) white dots on the underside of leaves (these are the eggs).
•Little buggers (depending on them ol' peepers of yours, you may need a magnifying glass to spot them!)

Treating a Spider Mite Infestation.

These practices can help control and eliminate a mite infestation when implemented carefully and deliberately.

I will begin by listing simple treatments and progress toward more complicated/severe treatments that may be required for heavily infested plants. The first course of action is to isolate infested plants in order to reduce the possibility of mite migration to mite-free plants. Keep your humidity levels up, but be careful if you're already in flowering as you don't want to induce fungal growth in your buds! Remember to water your plants 1/2 hour before spraying, as this will help reduce the amount of spray solution that is absorbed by your plants.

•Soap & Water - Mix a dilute solution of non anti-bacterial dish soap and water, and spray (fine mist) the leaves of your plant, particularly the underside where the mites like to live. May require multiple applications depending on how well you can cover each individual leaf of the plant. Make sure to rinse off the leaves with plain water 20 minutes after spraying in order to prevent the soap from clogging up the stomata on the leaves, which will stunt plant growth if not cared for.

•Soap & Water Plus Version 1 - Gather 1/4 cup baking soda, 1/2 cup apple cider vinegar, 1 tablespoon lemon juice, 2 drops dish detergent & 1/4 teaspoon epsom salt. Take one cup of hot water to dissolve epsom salts and pour into a clean 2 liter container with the rest of the ingredients. Add water to fill to 48 ounces (a 2 liter bottle will be 3/4 full) and shake well. Put into a spray bottle and cover your soil/medium with plastic. With the lights off, mist the plant all over concentrating on the underside of leaves. Wait 20 minutes and sprits off with clean fresh water, shaking as much water off the plant as you can. Solution is alkaline and rinsing is important in order to remove mites and eggs, and to prevent the solution from burning the plant leaves. Test on a small portion of the plant and wait 24 hours to observe before dousing the whole thing. If you see plant damage, dilute with more plain water and test again.

•Soap & Water Plus Version 2 - Gather 1/2 cup baking soda, 1 cup vinegar, 3 tablespoons lemon juice, 2 drops dish soap, mix and dilute with plain water to 40 fluid ounces. Use in the same manner as Version 1. Shown to work both indoor and out, with success on spider mites, thrips, aphids, clover mites, grass gnats and mosquitos.

•Soap & Water Variations - Since all plants will have varying degrees of sensitivity to these sprays, you can try to create your own by mixing water with a small amount of dish soap, as well as garlic, cinnamon, clove oil and lemon juice.

•Rubbing Alcohol - This poisonous liquid can kill mites and evaporate relatively quickly in order to reduce harm to plants. Varying degrees of success have been reported with solutions ranging from 1:3 (light) to 1:1 (strong) ratios of rubbing alcohol to water.

•Predatory Mites - These mites do not feed on plants but on other mites. Predatory mites can be mail-ordered from a horticultural warehouse or purchased online from gardening vendors. Three of the most common mites used to kill and control spider mites include Phytoseiulus persimilis, Metaseiulus occidentalis, and Phytoseiulus longpipes. The Phytoseiulus persimilis variety is nice because these guys cannibalizes on themselves after eating the problem mites, thereby reducing their own population naturally after they've finished their work. Phytoseiulus longpipes can stand higher temperatures, so if your grow space is above 89°F, you should try to find this variety.

•Miticides - When all else has failed, miticides will be one of the most effective forms of spider mite treatment. You should generally try not to use these more than necessary, as they are considerably more toxic than all of the above treatments, and can also cause resistant strains of mites if used repeatedly over time on the same population of mites.

Pyrethrins are natural organic compounds that provide potent insecticidal activity. While pyrethrins are slightly toxic, they are not very dangerous to humans and have been used as an organic crop dusting agent in agricultural farmling as well as indoor agriculture for some time. You can also find them in some shampoos designed to remove lice/ticks from humans and pets. Riptide 5.0% Pyrethrin is a common solution that works well.

Avid is a miticide/insecticide formulated by Syngenta corporation that will effectively kill spider mite populations. However, it is considerably more toxic than pyrethrin based insecticides. and should never be applied to plants that have already started their flowering phase. Avid is suitable for outdoor use while the plants are still in their vegetative state.

I hope that this has helped you to understand spider mite infestation and how to effectively deal with it. Most methods of treatment do not kill the mite eggs and will require re-treatment about 7 - 10 days after initial treatment. I'm sure that once you have dealt with an infestation, you will understand why prevention through cleanliness is well worth the effort if you want to have a hassle free, productive and bountiful grow.
(chopped/mixed and edited by me and other sources).



Active Member
Re: Spider mites.

What about soy oil based sprays for the small black flys we get here in the desert? Seems to work ok, but the best I can hope for is 22% humidity. Usually stays around 16%.(Indoor, closet and cabinet growing)
Mainly wondering about the soy oil seeping too far into the soil and getting to the roots.
Your thoughts?
Regards Deacn


Re: Spider mites.

What about soy oil based sprays for the small black flys we get here in the desert? Seems to work ok, but the best I can hope for is 22% humidity. Usually stays around 16%.(Indoor, closet and cabinet growing)
Mainly wondering about the soy oil seeping too far into the soil and getting to the roots.
Your thoughts?
Regards Deacn

Firstly the humidity is too low and there are many sprays suitable for all kinds of bugs. I have only ever had to deal with spider mites and its the worst thing that can happen.

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