I’ve had the most success with using environmental controls to combat spider mites. Keep in mind that mites love hot and dry temperatures. Mite reproduction seriously slows down at about 52 degrees F. At 48 degrees, it just about stops all together. If you can bring it down to 40-42, you’ll successfully “freeze” a majority of your mite population.
Fifty is thought to be the minimum for most cannabis plants. Keep in mind, this is gonna be incredibly variety dependent. Indicas generally tolerate lower temperatures better than sativas. Plants with high-altitude or mountainous origins will be a bit more hardy than a variety hailing from a humid sea level climate. Pay attention to your plants and where they come from. Look for signs of stress and plants beginning to turn purple. Only you will be able to know what your temperature limit is for the plants you are growing.
Once you’ve knocked the mites back with temperature, spray down your plants with high pressured water. This water stream will knock mites off the plant and make the environment too wet for spider mites to thrive. After hitting them with the water spray, allow plants to dry before hitting them with Flying Skull “Nuke Em” insecticide to kill the remaining mites. Beyond this, a once weekly rotation of SNS 217 Mite Control -> Mite-X (or substitute a pyretherin based insecticide) -> Nuke Em should keep them under control for the remainder of the season.
After harvest, be sure to remove any and all bit of plant material that is remaining. A serious scrub down and disinfecting of your grow room will help to prevent future infestations. The room should be as sterile as possible to maximize results.