Spider mites & cannabis

Published Jan 25, 2019 05:33 p.m. ET
What causes them and how to get rid of them

 The spider mite is a member of the mite family called Tetranychidae. The Tetranychidae family consists of 1200 different species that all spend most of their lives underneath the leaves of plants. It is there that they will start producing webs and reproducing. Spider mites damage the host plant when they puncture the plant to feed. These irritating pests are known to feed on hundreds of different types of plants and are a common occurrence in house plants. While spider mites look like regular spiders, they are very different because they feast on the plants themselves, not the bugs that land in their webs. Spider mites damage cannabis and can be a huge pain in the neck for marijuana growers.

What causes spider mites?

There is no one wrong move that will result in a spider mite infestation. These mites can do well in cool, humid conditions or warm, dry conditions. Spider mites are not something that just appears out of nowhere even though it sometimes may feel like it. They can travel long distances and tend to spread the most during their most active season which is in the spring and will go dormant for the winter. If you live in a climate that never freezes you will be more likely to experience an infestation. While there may not be a specific cause that creates a spider mite infestation, there are preventative measures that can be taken to keep them at bay.

Spider mite prevention

In this case, an ounce of prevention is worth an entire pound of cure. Spider mites will decimate even the healthiest plant in mere days making treating a plant covered in them incredibly difficult. To prevent spider mites from taking over your weed plants it’s best to start using a prevention method as early as possible. In a plant’s life cycle the plant is at its most vulnerable when it is small. The best way to prevent a surprise spider mite visit is to keep your plants moist, well hydrated, and dust free.

1. Keeping plants hydrated
This doesn’t mean you have to hose anything down. Routinely watering your cannabis plants as needed will help to keep spider mites at bay. Spider mites can only spread to dry plants, so keep them misted and watered. Using cold water is recommended because mites can’t stand cool temperatures.
2. Keep plants free of dust
This one is most important for those who live in older homes with larger volumes of dust that circulates. Dust is used by spider mites to nest and lay eggs. Dust also protects spider mites from being eaten by predator mites that naturally exist and are not harmful to the plant. Misting, wiping with a cloth, and dusting a minimum of once every two weeks is suggested for maximum effectiveness.
3. Provide a humid environment
This can be done by misting your plants 2-4 times a day and keeping the temperature above 24C. Fill water collecting trays underneath the plant pots with water for more humidity.
4. Shade plant from direct sunlight
Spider mites thrive in a warm environment full of light. While this may not always be a reasonable option with indoor grown marijuana plants, if you are concerned about an outbreak happening, placing the plants in indirect sunlight by shading with a thin veil whenever possible.
5. Predatory mites
This one makes some a bit squeamish, but plants naturally tend to have some sort of living organism attached to them. To keep spider mites at bay, you can purchase and place predatory mites on your weed plant. Though not ideal for everyone this is by far the most effective and most natural way to prevent a spider mite infestation.

How to get rid of spider mites on weed?

Spider mites rapidly reproduce making them extremely difficult to kill before the damage to the host plant is done. There are several different ways you can try to kill them if you are already experiencing a full-blown invasion.

1. Ladybugs
Ladybugs will eat mites at an astonishing rate. While these bugs may not be enough on their own to completely get rid of the problem, they are a practical and effective addition when used to battle mites.
2. Soak the plant
If you have a large population already, you may want to consider hitting your plant with a high-pressure water spray three times a day. The trick is to make the water hit hard enough to work while also keeping the plant intact and undamaged. It’s suggested to soak the plant for three days in a row in the morning giving it all day to perk back up from the beating. This will remove the mite’s protective barrier of webbing and make them easier to kill. Without the web, they will slowly starve as the webbing is required for them to reach the leaves to feast on.
3. Vacuum
Not a preferred method, but vacuuming can be used to effectively remove adult mites from a plant if done carefully. Using a small handpiece accessory vacuum the underside of each leaf and then the plant’s stem.
Mites have been a nuisance amongst growers for thousands of years, and despite that, there are no sure-fire or guaranteed successful solutions. The best way to keep your plants safe is with a thorough inspection every single day and a proper care regime so that if you do find yourself with some, you are able to catch them early enough to hopefully save the plant and remember, the most effective treatment is always a preventative treatment. Hope you enjoyed some of our tips and tricks for combatting the notoriously difficult to manage spider mite.

Happy growing!


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