Chimera’s Journal on Spider Mites

Contributed by: Chimera
Thanks to: Bunz
Submitted: 07-19-2003
Images archived: 2003

Introduction

Image by: Green Shaman

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 two product by ‘Safers’: EndAll and Trounce.
The active ingredient in both is pyrethrum, but Endall is based on canola oil, Trounce is based on soap and alcohol. Get the Endall and Trounce concentrate bottles, mix your own spray from these at home… it’s much cheaper, and you will be able to use your own sprayer.

Note: Safer’s insecticidal soap is pretty much the same as Trounce. Trounce contains alcohol and pyrethrum as well, which will further help kill the bugs.

I like the Endall because it coats the entire surfaces of the leaves well, and seems to penetrate the eggs and kills some of them, where as the trounce doesn’t seem to kill the eggs.

I like to apply Endall generously first (Day 1), and let it soak overnight, then rinse with plain water in the morning. Twice a day (if possible) on Days 2-5 spray the plants down using the same pressure sprayer with plain water… make sure you get both top and bottoms of the leaves each time.

On Day 5 mix a batch of the trounce up and again, spray before lights out. Rinse in the morning, and on days 6-10 spray twice daily with plain water.

Day 10- repeat the cycle

This should have killed all the mites on the plants, unless your population is resistant to pyrethrum. If they are resistant, you might substitute a harsher chemical (ie kelthane (flinch) or Malathion (flinch) ) for the second application of Endall.

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.

[Editor?s note: spot spray if you have never used the chemical before to prevent damage to your entire crop. Never spray with HIDs on, and use appropriate protective gear]

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!