Spider mites love to infest cannabis gardens and eat your plants. Spider mites are not actually spiders, but they sure act like them with their web-weaving ways. Spider mites are actually tiny mites that only resemble spiders. The most common spider mite in the US is the “tetranychus urticae” AKA “two-spotted spider mite.” Spider mites spell bad news for cannabis plants. They reproduce quickly, feast on your plants, and eventually weave webs around your precious flowers, so you’ll want to avoid them AT ALL COSTS. Their ability to develop resistance to pest controls and their overall ability to demolish cannabis gardens should concern you. 

Home growers strive to avoid spider mites. They do it by regular observation of leaves and spider mite control practices.

1. Observe the undersides and tops of the leaves for signs of spider mites on your cannabis. 

Spider Mites will unfortunately show up in your cannabis plants unannounced. They don’t sing, carry signs or bite humans. But they leave behind their telltale sign, “spider mite bite marks” which are on the tops of the leaves. On the bottoms will be eggs and spider mites. So you’ve got to make it a priority to look at leaves closely.

Observation is key to spotting spider mites. First be ready to use your hands to look under the leaves. You can also use a flashlight from your phone. Some people are able to see them scurrying about the backside of leaves, while others need the aid of a jewelers scope. Either way, make sure they are inspected regularly to keep your plants happy and healthy. If you are seeing webs, you are certainly dealing with a spider mite infestation. Catch them before they create webbing. And don’t be surprised if you end up throwing away plants once in a while. It happens to many home-growers. Don’t worry, you are not alone. 

One important distinction to make with infestations is that if you see a few spider mites, you don’t have an infestation. An infestation can happen quickly, so don’t waste any time with implementing your mite control treatment plan. When you see a few spider mites under the leaves, remove those leaves right away. Cut them into a bag and get it out of the grow. 


2. Mite control strategies will help you prevent, eliminate and control spider mites.

A high humidity will slow down those spider mites, but be sure to use a variety of preventatives and killers in your home grow and don’t let up. You can of course, use organic strategies and biological techniques. Try using predatory mites, Captain Jack’s Garden Dust, Bug Buster O, Horticultural Oil, Plant Therapy or Green Cleaner. Some growers swear by neem oil (but no one is spraying during flowering – it would cause your flowers to smell absolutely horrible), but many people are not comfortable using neem oil and it’s a very contentious issue in the pest control world. 

In severe cases, rotate products every 3 – 4 days. As a note, you need to kill the spider mite adults and the eggs too. Horticultural oil is known to smother the eggs, so be sure to add it to your arsenal. 

And don’t forget, when you have leaves with tons of spider mites crawling, cut the leaves into a bag and get it out of your garden at once. As a general rule: avoid foliar spraying during the flowering growth phase. Most growers don’t do foliage sprays after flower week 2 or 3 the latest. 

About predatory mites for spider mites: there are a wide variety of predatory mites to kill spider mites like Californicus, Percimillis, and Andersoni. There is even a type of lady bug who is a real spider mite killer called Stethorus Punctillum. These lady bugs are black, not red. Red ladybugs which we all love and know are not spider mite killers (but they kill aphids.) If you want to prevent and eliminate spiders, predatory mites are your best biological friends.

Lastly, you’ll want to clean your grow room, grow tent, or green house if you’ve had spider mites. There are many ways to clean and disinfect including the individual use of Green Cleaner, bleach, hydrogen peroxide, or alcohols. If you’re only cleaning with 1 solution, try rotating them with another cleaner after 24 hrs of drying. Be thorough, be clean and be patient. Don’t rush the cleaning process because “better safe than sorry!”


Want to learn more about spider mites? Listen to what entomologist Matthew Gates has to say about spider mites. 


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